S2Biocomposite02_03_04th

1Natural Fibers, Biopolymers, andBiocomposites: An Introduction

Amar K. Mohanty, Manjusri Misra, Lawrence T. Drzal, Susan E. Selke,Bruce R. Harte, and Georg Hinrichsen

CONTENTS1.1 Introduction1.2 Motivation: Biobased Materials vs. Environmental Impact1.3 What Are Biocomposites?1.4 Natural/Biofibers as Reinforcements in Biocomposites1.5 Biodegradable/Biobased Polymers as Matrices for

Biocomposite Applications1.5.1 Biodegradable Polymers from Starch and Cellulose1.5.2 Biobased/Biodegradable Plastics from Soybeans

and Other Plant Resources1.5.3 Biodegradable Polyesters from Renewable Resources

and Petroleum Resources1.5.4 Biobased Polymeric Materials from Mixed Resources

(Renewable and Petroleum Resources)1.6 Biocomposites as Alternatives to Petroleum-Based Composites:

Recent Trends and Opportunities for the Future1.7 Sustainable Biobased Products: New Materials for a

New Economy1.8 ConclusionsAcknowledgmentsReferences

ABSTRACT Persistence of plastics in the environment, the shortage oflandfill space, the depletion of petroleum resources, concerns over emis-sions during incineration, and entrapment by and ingestion of pack-aging plastics by fish, fowl and animals have spurred efforts to develop

Copyright 2005 by Taylor & Francis

biodegradable/biobased plastics. This new generation of biobased poly-meric products is based on renewable biobased plant and agricultural stockand form the basis for a portfolio of sustainable, eco-efficient products thatcan compete in markets currently dominated by products based on petro-leum feedstock in applications such as packaging, automotives, buildingproducts, furniture and consumer goods. It is not necessary to produce 100%biobased materials as substitutes for petroleum-based materials immedi-ately. A viable solution is to combine petroleum and bioresources to producea useful product having the requisite cost-performance properties for real-world applications. Biopolymers or synthetic polymers reinforced with nat-ural/biofiber frequently termed 'biocomposites' can be viable alternatives toglass fiber reinforced composites. The combination of biofibers like kenaf,industrial hemp, flax, jute, henequen, pineapple leaf fiber, sisal, wood andvarious grasses with polymer matrices from both non-renewable (petroleum-based) and renewable resources to produce composite materials that arecompetitive with synthetic composites such as glass-polypropylene, glass-epoxies, etc., is gaining attention over the last decade. This chapter providesa general overview of biopolymers, natural biofibers, biocomposites and theresearch and applications of these materials. Biobased polymers such aspolylactic acid (PLA), polyhydroxybutyrate (PHB), cellulose esters, soy-based plastic, starch plastic, poly (trimethylene terephthalate), biobasedresins from functionalized vegetable oils and biocomposites are also intro-duced in the chapter along with petroleum derived biodegradable polymers.Detailed discussions about the chemical nature, processing, testing andproperties of these polymers, fibers and composites will be discussed in theremaining chapters of the book.

1.1 Introduction

As a result of a growing awareness of the interconnectivity of global envi-ronmental factors, principles of sustainability, industrial ecology, ecoeffi-ciency, and green chemistry and engineering are being integrated into thedevelopment of the next generation of materials, products, and processes.17

The depletion of petroleum resources coupled with increasing environmen-tal regulations are acting synergistically to provide the impetus for newmaterials and products that are compatible with the environment and inde-pendent of fossil fuels. Composite materials, especially green composites,fit well into this new paradigm shift. Simply stated, biobased materialsinclude industrial products for durable goods applications, made fromrenewable agricultural and forestry feed stocks, including wood, agricul-tural waste, grasses and natural plant fibers composed of carbohydratessuch as sugars and starch, lignin and cellulose, as well as vegetable oils andproteins. Producing chemical products and new materials from renewable


userHighlight

userHighlight

userHighlight

resources is not a new idea. Most of the chemical products and materialscame from renewable resources until the early part of the 20th century.1 Thesuccess and tremendous growth of the petrochemical industry in the 20thcentury, however, slowed the growth of biobased products. Environmentalas well as economic factors are now driving the trend toward greater uti-lization of biobased polymers and materials.25 The challenge to scientistsand engineers is to develop the technology needed to make the biobasedmaterials revolution a reality.

The production of chemicals and materials from biobased feedstocks1 isexpected to increase from todays 5% level to ~12% in 2010, ~18% in 2020,and ~25% in 2030. Expectations are that two-thirds of the $1.5 trillion global chemical industry can eventually be based on renewable resources.The U.S. agricultural, forestry, life sciences, and chemical communities havedeveloped a strategic vision6 for using crops, trees, and agricultural residuesto manufacture industrial products, and have identified major barriers7 to itsimplementation. The Technology Road Map for Plant/Crop-basedRenewable Resources 2020, developed by the U.S. Department ofAgriculture (USDA) and the U.S. Department of Energy (DOE), has set a tar-get of 10% of basic chemical building blocks arising from plant-derivedrenewables by 2020, with developed concepts in place by then to achieve afurther increase to 50% by 2050.

Petroleum transitioned from a single product (kerosene in the early 1900s)to a multiproduct industry (fuel gas, gasoline, jet fuel, naphtha, diesel fuel,asphalt, chemicals, etc.) between the late 19th century and the middle of the20th century. Research conducted from the 1990s to the present has led tomany new biobased products.814 Some examples include polylactic acid(PLA) from corn; polyurethane products from soy oil; soy protein adhesives;solvents from soy and corn oil; lubricants from vegetable oil; thermoset andthermoplastic polymers from soy and corn; organic acids from crop sources;and biocomposites from lignocellulosic fibers combined with petroleum-based polymers like polypropylene (PP) and polyethylene (PE), or biopoly-mers like PLA, cellulose esters, polyhydroxyalkanoates, and vegetableoil-based bioresins. Recent advances in genetic engineering, natural fiberdevelopment, and composite science offer significant opportunities for new,improved materials from renewable resources, which can be biodegradableand recyclable but also obtained from sustainable sources at the same time.

The persistence of plastics in the environment, the shortage of landfillspace, concerns over emissions during incineration, and entrapment andingestion hazards from these materials have spurred efforts to developbiodegradable plastics. Several of the worlds largest chemical companies,including DuPont, Monsanto, Dow, and Cargill have announced a major shiftin their base science and technology from traditional petrochemical process-ing to life sciences.15 DuPont and Monsanto have invested $12.5 billion toacquire expertise in agricultural biotechnology.16 Biopolymers are nowstarting to migrate into the mainstream and biobased polymers may soon becompeting with commodity plastics. The best examples of biopolymers


userHighlight

userHighlight

userHighlight

userHighlight

userHighlight

derived from renewable resources are cellulosic plastics like celluloseacetate, starch plastics like starch esters, and corn-derived plastics, i.e., PLA(polylactic acid). Sales growth rates of more than 2030%/yr are expectedalong with improved economics as production and sales increase. The chal-lenge in replacing conventional plastics with biodegradable materials is todesign materials that exhibit structural and functional stability during stor-age and use, yet are susceptible to microbial and environmental degradationonly upon disposal and without any significant environmental impacts.

1.2 Motivation: Biobased Materials vs. Environmental Impact

The successful transition to a biobased economy challenges the global aca-demia, government, and industry. The world technology (WTEC) panelreport17 has reviewed the status of environmentally benign manufacturing(EBM) technologies, applications, and policies in Europe and Japan in com-parison to those in the United States. In this report, the main focus was givento polymers, electronics, transportation applications, and energy-relatedissues as well as the broader issues of government policies affecting envi-ronmental issues. The Biomass Research and Development Act of 2000 (U.S.Public Law 106-224), presidential executive orders 13134 (calling for triplingAmericas use of biobased products by 2010) and 13101 (greening the gov-ernment through recycling and waste prevention), and the Farm Securityand Rural Investment Act of 2002 (Public Law 107-17), also known as the2002 Farm Bill, together are creating an environment where there is an eco-nomic incentive to seriously consider biobased alternatives to petroleum-based materials. Biobased alternatives would play a role in reducing U.S.dependence on foreign oil. Biobased product development would have sig-nificant benefits for our citizens and society.

1.3 What Are Biocomposites?

Composite materials are attractive because they combine material propertiesin ways not found in nature. Such materials often result in lightweight struc-tures having high stiffness and tailored properties for specific applications,thereby saving weight and reducing energy needs. Fiber-reinforced plasticcomposites began with cellulose fiber in phenolics in 1908, later extending tourea and melamine, and reaching commodity status in the 1940s with glassfiber in unsaturated polyesters. From guitars, tennis racquets, and cars tomicrolight aircrafts, electronic components, and artificial joints, compositesare finding use in diverse fields. The fiber-reinforced composites market


userHighlight

userHighlight

userHighlight

userHighlight

userHighlight

userHighlight

userHighlight

(Figure 1.1) is a multibillion-dollar business.18 Glass fiber is the dominantfiber and is used in 95% of cases to reinforce thermoplastic and thermosetcomposites. Current research findings show that in certain composite appli-cations, natural fibers demonstrate competitive performance to glass fibers.Broadly defined, biocomposites (Figure 1.2) are composite materials madefrom natural fiber and petroleum-derived nonbiodegradable polymers likePP, PE, and epoxies or biopolymers like PLA and PHAs. Composite materi-als derived from biopolymer and synthetic fibers such as glass and carbonalso come under biocomposites. Biocomposites derived from plant-derivedfiber (natural/biofiber) and crop/bioderived plastic (biopolymer/bioplas-tic) are likely more ecofriendly, and such biocomposites are sometimestermed green composites.

31%

26%

12%

10%

8%

8%4%

(1%) Aerospace Miscellaneous

Automotives

Construction

Marine

Electronic components

Appliances

Consumer products

FIGURE 1.1Fiber-reinforced plastic composites used in 2002 2.28 3 109 lb. (Adapted from Plast. News.August 26, 2002.)

Natural/biofiber composites (biocomposites*)

Hybrid biocomposites(fiber blending/matrix blending)

*Composites made from synthetic fiber; likeglass and bioplastic; like PLA can also come under biocomposite,,

Partly ecofriendly Ecofriendly/green

Biofiber-petroleum-based plastic

(polypropylene/polyester, etc.)

Biofiber-renewableresource-based bioplastic

(soy plastic/cellulosic plastic/PLA, etc.)

FIGURE 1.2Classification of biobased composites.


After decades of development of high-performance artificial fibers like car-bon, aramid, and glass, natural fibers have gained renewed interest, espe-cially as a glass fiber substitute in automotive industries. Advantages ofnatural fibers over synthetic or man-made fibers such as glass and carbon areas follows: low cost, low density, acceptable specific strength properties, easeof separation, carbon dioxide sequestration, and biodegradability. Naturalfiber composites are now emerging as a realistic alternative to wood-filledand glass-reinforced plastics. Ecofriendly biocomposites have the potential tobe the new material of the 21st century and be a partial solution to manyglobal environmental problems.

1.4 Natural/Biofibers as Reinforcements in Biocomposites

The worlds supply of natural resources is decreasing and the demand forsustainable and renewable raw materials continues to rise. In 1997, approx-imately 25 million metric tons of man-made fibers and about 20 million met-ric tons of natural fibers were produced worldwide.19 Biofiber-reinforcedcomposites represent a potential nontraditional, value-added source ofincome to the agricultural community.3 Jute is from India and Bangladesh;coir is produced in the tropical countries of the world, with India account-ing for 20% of the total world production; sisal is also widely grown in trop-ical countries of Africa, the West Indies, and the Far East, with Tanzania andBrazil being the two main producing countries; kenaf is grown commer-cially in the United States; flax is a commodity crop grown in the EuropeanUnion as well as in many diverse agricultural systems and environmentsthroughout the world, including Canada, Argentina, India, and Russia. Flaxfiber accounts for less than 2% of world consumption of apparel and indus-trial textiles, despite the fact that it has a number of unique and beneficialproperties. Hemp originated in Central Asia, from which it spread to China,and is now cultivated in many countries in the temperate zone. Ramie fibersare the longest and one of the strongest fine textile fibers and mostly avail-able and used in China, Japan, and Malaysia. The price for natural fibervaries depending on the economy of the countries where such fibers areproduced.

Most plastics by themselves are not suitable for load-bearing applicationsdue to their lack of sufficient strength, stiffness, and dimensional stability.However, fibers possess high strength and stiffness but are difficult to use inload-bearing applications by themselves because of their fibrous structure.In fiber-reinforced composites, the fibers serve as reinforcement by givingstrength and stiffness to the structure while the plastic matrix serves as theadhesive to hold the fibers in place so that suitable structural componentscan be made. A broad classification (nonwood and wood fibers) of naturalfibers is represented schematically in Figure 1.3, whereas Figure 1.4 displaysimages of several natural fibers with reinforcement potential.


userHighlight

userHighlight

Currently several nonwood fibers (e.g., hemp, kenaf, flax, and sisal) arebeing utilized commercially in biocomposites in combination withpolypropylene for automotive applications. More details on various plant

Bast Leaf Seed/fruit

Examples:

Reinforcing natural/biofibers

Nonwood natural/biofibers Wood fibers

Strawfibers

Grassfibers

Recycledwood fibers

Examples:Newspaper/magazine

fibers

Examples:Soft and

hard woodsExamples

Cotton, coir

Examples:Kenaf, flax,jute, hemp

Examples:Bamboo fiber, switch

grass, elephant grass Rice/wheat/corn straws

Examples:Henequen, sisal,

pineapple leaf fiber

FIGURE 1.3Schematic representation of reinforcing natural/biofibers classification.

FIGURE 1.4Digital photographs of some natural fibers and sources of natural fibers.


fibers, the processing of bast fiber plants, and retting of natural fibers can befound in Chapters 24 of this book. Native grass fibers also are gaining theattention of scientists as reinforcing fibers for biocomposites applications.20,21

Similarly, recycled wood fibers such as newspaper fibers are another viablepotential source of fiber reinforcement.22 Straw fibers from rice, wheat, orcorn are widely available in different parts of the world and can also be usedas very inexpensive reinforcements for biocomposites.23 Chapter 14 discussesmore about straw-based biomass and biocomposites whereas the alternativelow-cost biomass for the biocomposite industry is discussed in Chapter 5.

Thermoplastic/wood composites have been known for many years.24 Theproduction of wood-plastic composites has grown fourfold25 between theyears 1997 and 2000. Thermoplastics like polyethylene (PE), polypropylene(PP), and polyvinyl chloride (PVC) are widely used in wood-plastic com-posite industries.26 Historically, most of these used wood flour to producefilled plastics. The wood flour decreased the cost, but was not usuallyintended to improve the performance in any substantial way.

All natural fibers, whether wood or nonwood types, are cellulosic in nature.The major constituents of natural biofibers are cellulose and lignin. Theamount of cellulose, in lignocellulosic systems, can vary depending on thespecies and age of the plant. Cellulose is a hydrophilic glucan polymer con-sisting of a linear chain of 1,4- anhydroglucose units, which contain alcoholichydroxyl groups (Figure 1.5). These hydroxyl groups form intermolecular andintramolecular hydrogen bonds with the macromolecule itself and also withother cellulose macromolecules or polar molecules. Therefore, all natural fibersare hydrophilic in nature. Although the chemical structure of cellulose fromdifferent natural fibers is the same, the degree of polymerization (DP) varies.The mechanical properties of a fiber are significantly dependent on the DP.

During the biological synthesis of plant cell walls, polysaccharides such ascellulose and hemicellulose are produced, and simultaneously lignin fills thespaces between the polysaccharide fibers, cementing them together. Thislignification process causes a stiffening of cell walls, and the carbohydrate isprotected from chemical and physical damage. Lignin is a biochemicalpolymer that functions as a structural support material in plants. Lignin is ahigh molecular-weight phenolic compound, generally resistant to microbialdegradation. The exact chemical nature of lignin still remains obscure.

OCH2OH CH2OH

CH2OHCH2OH

H

HO

H HH

OH

OH

HO

H HOH

H

H

OH

HH O

H

H

OH

OH OHH

OHH

O

HO

H O

H O

H

H

OH

n

FIGURE 1.5Cellulose structure.


userHighlight

userHighlight

userHighlight

The main difficulty in lignin chemistry is that no method has been estab-lished by which it is possible to isolate the lignin in its native state from thefiber. The chemical nature of lignin in lignocellulosic materials has been animportant subject of study. A probable structure of lignin27 is represented inFigure 1.6. Although the exact structural formula of lignin has not yet beenestablished, most of the functional groups and units, which make up themolecule, have been identified. The high carbon and low hydrogen contentof lignin suggest that it is highly unsaturated or aromatic in nature. Lignin ischaracterized by its associated hydroxyl and methoxy groups. The topologyof lignin from different sources may be different but it has the same basiccomposition. Although the exact mode of linkages of lignin with cellulose inlignocellulosic natural fiber is not well known, lignin is believed to be linkedwith the carbohydrate moiety through two types of linkages, one alkali sen-sitive and the other alkali resistant. The alkali-sensitive linkage forms anester-type combination between lignin hydroxyls and carboxyls of hemicel-lulose uronic acid. The ether-type linkage occurs through the lignin hydrox-yls combining with the hydroxyls of cellulose. The lignin, beingpolyfunctional, exists in combination with more than one neighboring chainmolecule of cellulose and/or hemicellulose, making a cross-linked structure.

The tensile strengths as well as Youngs modulus of natural fibers likekenaf, hemp, flax, jute, and sisal are lower than that of E-glass fiber com-monly used in composites. However, the density of E-glass is high, ~2.5 g/cc,while that of natural fibers is much lower (~1.4 g/cc). The specific strengthand specific moduli of some of these natural fibers are quite comparable toglass fibers.3,4 This becomes particularly important where the weight of thestructure needs to be reduced. The chemical compositions as well as proper-ties of different natural fibers are discussed in more detail by Bismarck et al.in Chapter 2. The place of origin and climatic conditions also affect the physi-comechanical properties of these natural fibers. To create confidence in the

OHOH

OOCH3

OHOH

O

CH3O

OCH3O

OHOH

HO

HO

HOO

CH3O OCH3O

O

OH

OCH3

OH

OHOH

OCH3

HO

O

OH

OCH3

OCH3O

OH

OHOH

CH3O

OH

OH OH

OH

OOCH3

OH

OHCH3O

OCH3OO

OCH3O

HO

FIGURE 1.6Lignin structure. (Adapted from Rouchi, A.M., Chem. Eng. News, Nov. 13, 2000, pp. 2932.)


userHighlight

userHighlight

userHighlight

consistent quality of specific biofibers among the industrial users is a seriouschallenge to researchers. Genetic manipulation, which produces fibers withlow lignin content and with consistent properties is poised to produce a newgeneration of cellulose-rich biofibers for wide-scale industrial uses.

1.5 Biodegradable/Biobased Polymers as Matrices forBiocomposite Applications

The classification of biodegradable/biobased polymers is represented inFigure 1.7. Biobased polymers may or may not be biodegradable, dependingon their composition and structure as well as on the environment in whichthey are placed.

Renewable sources of polymeric materials offer an answer to maintainingthe sustainable development of economically and ecologically attractivetechnology. The innovations in the development of materials from biopoly-mers, the preservation of fossil-based raw materials, complete biologicaldegradability, the reduction in the volume of waste and compostability,reduction of atmospheric carbon dioxide released, as well as increased uti-lization of agricultural resources for the production of new green materialsare some of the reasons for the increased public interest. Biodegradable poly-mers have offered scientists a possible solution to waste disposal problems

Aliphatic polyesters

Aliphatic-aromaticpolyesters

Poly(ester amide)

Poly(alkyenesuccinate)s

Poly(vinyl alcohol)

Polyhydroxy-alkanoates (PHAs)

Polylactides (PLA)

Cellulose esters

Starch plastics

SORONATM (condensation polymer of corn-derived 1,3 propane diol & petroleum- derived terephthalic acid)Blendings of:

Two/more biodegradable polymers(example: starch plastic + PLA)

One biodegradable + onefossil fuel-made polymer(example: starch plastic+ polyethylene)Epoxidized soybean oil +petro-based epoxy resin

Biodegradable/biobased polymers

Successful blending: newpolymeric materials of desired

properties(such materials may be termedas biobased & may or may not

be biodegradable)

Renewableresource-based

Petroleum/fossilfuel-based

Mixed resource-based:renewable resources +petroleum resources

FIGURE 1.7Broad classification of biodegradable polymers/biobased polymers.


userHighlight

associated with traditional petroleum-derived plastics. Rising oil priceshelped to stimulate early interest in biodegradables in the 1970s, and con-cerns over the dwindling availability of landfill sites, environmental regula-tions, and increasing oil prices are reviving interest in biodegradablematerials today. Biodegradable polymers may be defined3 as those whichundergo microbially induced chain scission leading to photodegradation,oxidation, and hydrolysis, which can alter the polymer during the degrada-tion process. Another definition states that biodegradable polymers arecapable of undergoing decomposition primarily through enzymatic action ofmicroorganisms to carbon dioxide, methane, inorganic compounds, or bio-mass in a specified period of time. The biopolymers may be obtained fromrenewable resources and also can be synthesized from petroleum-basedchemicals. Blending of two or more biopolymers can produce a new biopoly-mer designed for specific requirements. Biodegradability is not only a func-tion of origin but also of its chemical structure and degrading environment.When a biodegradable material (neat polymer, blended product, or compos-ite) is obtained completely from renewable resources, it may be termed as agreen polymeric material. The life cycle of compostable biodegradable poly-mers is represented schematically in Figure 1.8.

Processing

Sunlight

Innovation:Polymer production

Biodegradation

H2O + CO2

Photosynthesis

Use & discard

Photosynthesis

Natural resources

FIGURE 1.8Life cycle of biodegradable polymers can maintain CO2 balance in the environment.


Traditional plastics like polypropylene, polyethylene, polyester, andepoxy have a development history and have attained adequate status incomposite applications. Several biodegradable polymers need to be devel-oped so as to make them suitable as matrix polymers for composite applica-tions. Originally biopolymers were intended to be used in packaging,farming, and other industries with minor strength requirements. The per-formance limitations and high cost of biopolymers are major barriers fortheir widespread acceptance as substitutes for traditional nonbiodegradablepolymers. The high cost of some biopolymers as compared to traditionalplastics is not due to the raw material costs for biopolymer synthesis butmainly to the low volume of production. New and emerging applications ofbiopolymers need to be developed for their high-volume applications. Thechallenge for development of biodegradable polymers lies in the fact thatthey should be stable during storage or use and again should degrade onlywhen they are disposed of after their intended lifetime. Biopolymers rein-forced with biofibers can produce novel biocomposites to replace and sub-stitute for glass fiber-reinforced composites in various applications.

1.5.1 Biodegradable Polymers from Starch and Cellulose

Biopolymers evolved to function as cellular components of the organisms. Inorder to produce useful plastics from biopolymers, biopolymers have to bemodified. The best-known renewable resources capable of makingbiodegradable plastics are starch28,29 and cellulose.30 More detailed descrip-tions of cellulose ester and starch plastics can be found in Chapters 19 and20, respectively, of this book.

Starch and cellulose are not plastics in their native form, but are convertedinto plastics through various approaches, including extrusion cooking, func-tionalization, and plasticization. Starch is one of the least expensivebiodegradable materials available in the world market today. It is a versatilebiopolymer with immense potential for use in non-food industries. Starch-based polymers can be produced from corn, rice, wheat, or potatoes. Starchis produced in plants and is a mixture of linear amylose (poly--1,4-D-glu-copyranoside) and branched amylopectin (poly--1,4-D-glucopyranosideand -1,6-D-glucopyranoside). Starch can be made thermoplastic throughdestructurization in the presence of specific amounts of plasticizers (waterand/or polyalcohols) under specific extrusion conditions. Three phenomena(i.e., fragmentation of starch granules, hydrogen-bond cleavage betweenstarch molecules leading to loss of crystallinity, and partial depolymeriza-tion of the virgin starch polymers) generally occur during conversion ofstarch to starch plastic under extrusion conditions. Unmodified thermoplas-tic starch alone can be processed as a traditional plastic; however, its sensi-tivity to humidity makes it unsuitable for many applications. Unmodifiedthermoplastic starch is mainly used in soluble compostable foams, loose-fillmaterials, expanded trays, shape-molded parts and expanded layers, and as


a replacement for polystyrene. Poly(-caprolactone), PCL, a fossil fuel- orpetroleum-derived synthetic biodegradable polymer, provides water resist-ance to starch-based formulations, making them attractive for commercialenterprises. The strength and stiffness of starch plastic is enhanced consid-erably31 as a result of reinforcement with surface-treated jute fibers, and bio-composites made with 50 wt% jute improve the tensile strength of virginstarch plastic by more than 150%.

Cellulose from trees and cotton plants is a substitute for petroleum feed-stocks to make cellulosic plastics.30 The structures of cellulose esters includ-ing cellulose acetate (CA), cellulose acetate propionate (CAP), and celluloseacetate butyrate (CAB) are represented in Figure 1.9. CAB and CAP are nowused in a variety of plastic applications. For instance, premium toothbrushhandles are typically made of CAP, and screwdriver handles are often madefrom CAB. Recently, cellulosic plastics have gained importance in biocom-posite formulations.32,33 Chapter 19 discusses biobased composite materialsfrom cellulose esters and natural fibers.

1.5.2 Biobased/Biodegradable Plastics from Soybeans and Other PlantResources

In recent years, engineering of bioplastics and biobased materials fromplant-based proteins and oils has gained global attention. Considering theimportance of the research and development in this area as well as the com-mercial value of such protein and vegetable oil-based biobased materials, theeditors have included four chapters (Chapters 2225) describing recentdevelopments. In the United States, soybeans provide over 60% of the fatsand oils used for food. Research on applications of soybeans for non-fooduses in plastics and composites is under way at various U.S. universities.Soybeans typically contain about 20% oil and 40% protein. Soy protein isavailable in three different forms as soy flour, soy isolate, and soy concen-trate. Soy protein, soy meal, and soy oil from soybean can be converted toplastic resins.

OCH2OR

CH2OR

CH2OR

CH2OR

OOR

OR

OROROH

OO

O

O OHO

OROR

OR

ORn

n = 400750; R = H (cellulose), acetyl (cellulose acetate), acetyl and propionyl(cellulose acetate propionate), or acetyl and butyryl (cellulose acetate butyrate)

FIGURE 1.9Structures of cellulose esters.


Chemically, soy protein is an amino acid polymer or polypeptide whilesoy oil is a triglyceride. Through extrusion processing and blending technol-ogy, soy protein polymers are converted into biodegradable plastics,34

whereas through fuctionalization of soy oil, a matrix resin suitable for natu-ral fiber composites is also reported.35 Soy protein-based bioplastics are ther-moplastics and likely to be biodegradable. Soy oil-based resins are usuallythermosets and likely to be nonbiodegradable, based on the existing litera-ture. Green composites from soy protein-based bioplastics and naturalfibers3638 show potential for rigid packaging and even for housing andtransportation applications.

1.5.3 Biodegradable Polyesters from Renewable Resources and PetroleumResources

Biodegradability is not only a function of origin but also of chemical struc-ture and degrading environment. Sometimes thermoset bioresins, even ifmade or derived from bioresources, may not be biodegradable. The chemi-cal structures of some important members of the polyester class ofbiodegradable polymers are represented in Figure 1.10. PLA as well as PHAsare renewable resource-based biopolyesters, in contrast to PCL, PBS andaliphatic-aromatic polyesters, which are petroleum-based biodegradablepolyesters. Aliphatic polyesters are readily biodegradable, whereas aromaticpolyesters like poly(ethylene terephthalate) (PET), are nonbiodegradable.However, aliphatic-aromatic copolyesters have been shown to be biodegrad-able, and recently these polyesters have gained commercial interest, espe-cially for packaging applications.39 Eastmans Easter Bio and BASFsEcoflex are two examples of aliphatic-aromatic copolyesters based onbutanediol, adipic acid, and terephthalic acid. Eastar Bio is highly linear instructure while Ecoflex has a long-chain branched structure.

As early as 1973, the biodegradability of PCL was demonstrated.40 It is atough and semirigid material at room temperature with a modulus betweenlow-density and high-density polyethylene.3 PCL has a low melting point(~60C), low viscosity, and can be melt processed easily. It possesses goodwater, oil, solvent, and chlorine resistance. PCL is widely used as a blendingpartner with a number of polymers, especially with hydrophilic starch plas-tic.41,42 Biocomposites from PCL and natural fibers have been developed.43

The tensile strength and Youngs modulus of PCL improved by 450% and115%, respectively, after reinforcement with 40 wt% wood flour. Poly(alky-lene dicarboxylate) biodegradable aliphatic polyesters have been developedby Showa Highpolymer under the trade name Bionolle. Different grades ofBionolle include polybutylene succinate (PBS), poly(butylene succinate-co-butylene adipate) (PBSA), and poly(ethylene succinate). SK Chemicals alsoproduces aliphatic PBS polyesters. DuPont`s biodegradable Biomax copoly-ester resin, a modified form of PET, was launched in 1997. Its properties,according to DuPont, are diverse and customizable, but they are generally


formulated to mimic polyethylene or polypropylene.44 The biodegradableplastics from polyesters are mostly used in packaging applications.

PLA, a polymer of the relatively simple lactide molecule, is not a newpolymer. The manufacture of polyester from lactic acid was pioneered in1932 by Carothers45 and further developed by DuPont46 and Ethicon. The useof PLA in biomedical applications47 began in the 1970s. High production

O

CCH

n

(O2 x)

O

x C

O

O CCHn

(O2) yHC( 2)

O (CH2)4O

CC (CH2)4CO

O O CO O

H2C CR

CHn

O

O

CRCH

n

OO R = H, Poly(glycolic acid), PGA

R = CH3, Poly(lactic acid), PLA

R = CH3, Poly(-hydroxybutyrate), PHB R = CH3, C2H5, Poly(-hydroxybutyrate-co-valerate), PHBV copolymer

Poly(-hydroxyalkanoate)

x = 5, Poly(-caprolactone), PCL

x = 4, y = 2; Poly(butylene succinate), PBSx = 4, y = 2,4, Poly(butylene succinate-co-butylene adipate), PBSA

Poly(alkylene dicarboxylate)

Aliphatic-aromatic polyester

Aliphatic polyesters

Poly(-hydroxy acid)

Poly(-hydroxy acid)

Chemical Structures Examples

H CCCHn

O

2

CH3O

m

(Hydroxybutyrate, HB) (Hydroxyvalerate, HV)PHBV copolymer containing HB and HV units

H CCCHO

2 O

C2H5

FIGURE 1.10Structures of some aliphatic and aliphatic-aromatic polyesters (biodegradable polymers ofcommercial interest).


costs restricted the applicability of these polymers outside the medical fielduntil the late 1980s. Recent developments in the economical manufacture ofmonomer of PLA from agricultural products has placed this material at theforefront of the emerging biodegradable plastics industries. Polylactide(PLA) is a highly versatile biopolymer derived from renewable resourceslike corn.48 The use of PLA as a cost-effective alternative to commodity petro-leum-based plastic will increase the demand for agricultural products. ACargill-Dow plant in Nebraska is capable of producing 300 million poundsof renewable resource-based PLA per year from 40,000 bushels of corn perday. More details on PLA technology are in Chapter 16. Cargill-Dow uses asolvent-free process and a novel distillation process49 in contrast to MitsuiChemicals, which uses a solvent-based process50 to make high molecular-weight PLA. Biocomposites from natural fiber and PLA have useful proper-ties5153 and are discussed more in Chapter 17.

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters, which areproduced by bacterial fermentation. The first PHA discovered was polyhy-droxybutyrate (PHB). Figure 1.11 shows a photograph of the formation of bac-terial polyesters during fermentation by microorganisms. PHA polymers aresynthesized in the bodies of bacteria fed with glucose (e.g., from sugarcane)in a fermentation plant. Over one hundred PHA compositions have beenreported in the literature. In the late 1980s, ICI Zeneca commercialized PHAsproduced by microbial fermentation under the trade name Biopol. PHB andthe copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) werealso produced by Monsanto and sold under the trade name Biopol.

White patches in microorganism are PHB

FIGURE 1.11Photograph showing bacterial polyester (PHB) formation during fermentation by microorganisms. (Courtesy: Biomer, Germany.)


These bacterial polyesters were originally intended as biodegradable substi-tutes for oil-based polyolefins in films, bottles, and plastic containers.54 Theactual and potential uses of PHB and PHBV for containers, films, and paper-coating materials have been reviewed.55 In 1990, the manufacture of blow-molded bottles using Biopol for packaging shampoo was started in Germanyby Wella AG, Darmstadt. The range of possible uses of Biopol polymers hasbeen summarized by Amass et al.56 PHBVs are highly crystalline polymerswith melting points and glass transition temperatures similar to polypropy-lene (PP).57 Due to their characteristics of biodegradability through nontoxicintermediates and easy processibility, PHBV polymers are being developedand commercialized as ideal candidates for the substitution of nonbiodegrad-able polymeric materials in commodity applications.58,59 However, their highcost, the small difference between their melting and thermal degradation tem-peratures, and their low-impact resistance at ambient and subambient tem-peratures prevented their larger commercial applications. Recentdevelopments in bacterial polyester technology look promising. Differentcompanies such as Metabolix (Cambridge, MA), Proctor & Gamble, Biomer inGermany, and PHB Industrial S. A. in Brazil are pursuing commercializationpathways to make these bacterial polyesters competitive with traditionalpolyolefins like polyethylene and polypropylene. Metabolix recently pro-duced PHBV in a commercial-scale fermentation plant39 and is pursuing atransgenetic approach to develop PHAs from switchgrass. Proctor & Gambleis looking to commercialize their specific branched PHAs (Nodax). The long-chain branching of such polyesters allows a considerable range for tailoringthe crystallinity, stiffness, toughness, and melting point of the Nodax poly-mers. Green composites from PHAs and natural fibers5961 are gaining impor-tance in recent years. This area is comprehensively discussed in Chapter 18.

The strength of biodegradable polyester may be increased by substitutinga fraction of ester links by amide groups. On a call from the Government ofGermany for research and development on biodegradable thermoplasticswith good performance and processing behavior, Bayer, in 1990, presentedtwo grades of polyester amides,62 namely, BAK 1095 and BAK 2095. BAK1095 is based on caprolactam (Nylon 6), butanediol, and adipic acid, whereasBAK 2195 is synthesized from adipic acid and hexamethylene diamine(Nylon 6,6) and adipic acid with butanediol and diethylene glycol as estercomponents. BAK 1095 has mechanical and thermal properties resemblingthose of polyethylene.63 The resin is also noted for its high toughness and ten-sile strain at break. It can be processed into film and also into extruded andblow-molded parts. It is suitable for thermoforming and can be colored,printed, hot-sealed, and welded. BAK 2195 resin is an injection-moldinggrade biodegradable thermoplastic that exhibits greater stiffness. The prop-erty profile of BAK 2195 can also be extended through the addition of fillersand reinforcing substances, such as starch, natural fibers, wood flour, andminerals.64 The combined performance of both BAK grades and the com-pounds open a wide range of applications like disposable plant pots, agricul-tural films, biowaste bags, plant clips, cemetery decorations, and one-way


TAB

LE 1

.1

Pro

per

ties

of

So

me

Tra

dit

ion

al P

oly

mer

s an

d B

iod

egra

dab

le P

oly

mer

s

PB

S

PL

AP

HB

P

CL

BA

KE

ast

er

(Bio

no

lle 1

001

b)

Pro

pert

y(E

co-P

LA

)(P

226

a)

PH

BV

(To

ne 7

87)

1095

Bio

Eco

flex

Fil

m G

rad

eP

SL

DP

EP

P

Den

sity

(g

/cm

3 )1.

211.

251.

251.

145

1.07

1.22

1.25

1.26

1.04

1.0

90.

920.

90M

elti

ng

po

int

(C

)17

718

016

817

213

560

125

108

110

115

115

12

416

4T

ensi

le s

tres

s at

4524

27

2541

2522

3657

356

48

1034

bre

ak (

MP

a)T

ensi

le m

od

ulu

s28

0017

002

000

1000

386

220

100

80

2800

350

010

020

0

(MP

a)E

lon

gat

ion

36

925

900

400

700

820

700

12.

515

060

012

at b

reak

(%

)

aP

last

iciz

ed P

HB

, S

ourc

e: B

iom

er,

Ger

man

y, h

ttp

://

ww

w.b

iom

er.d

e/b

Fro

m t

ech

nic

al d

ata

shee

t, S

ho

wa

Hig

hp

oly

mer

Co

. L

td.

Copyright

2

005 b

y T

aylo

r &

Fra

ncis

dishes. BAK 1095 breaks down into water, carbon dioxide, and biomassunder aerobic conditions. The degradation rate is comparable to that of otherorganic materials that are composted.63 Bayer has recently withdrawn theproduction and sale of their polyester amide products.65

Table 1.1 represents some comparative properties2,6671 of a few traditionalpolymers and biodegradable polymers.

Biodegradable polymers will play a prominent role in plastic packagingapplications. In the United States alone, over 25 million tons of plastics enteredthe municipal solid waste stream (MSW), which is over 11% of the total MSWgeneration in the year 2001 (Figure 1.12, after ref. 72). Plastic packaging mate-rials are everywhere in our daily lives. Around $450 billion worth of packag-ing materials are used each year across the world. From food wrappings andcontainers to detergent and soft drink bottles to foam packaging used in ship-ping delicate goods, many products are surrounded by or contained in poly-meric materials. Packaging dominates the plastics use (Figure 1.13, after ref.73). It is forecasted that in the year 2005 more than $27 billion worth of plasticwill be used in packaging (Figure 1.14, after ref. 74). At present most polymericpackaging materials are based on nonrenewable fossil fuel feedstocks. Mostnotably, polyethylene is currently produced from ethylene gas, a product ofcracking of ethane, which comes from nonrenewable petroleum resources.Incineration of these materials makes a net contribution to atmospheric CO2,and plastics currently account for in excess of 20% of the nations landfill. Inaddition, many widely used materials, notably polystyrene and PVC, aremade from noxious or toxic monomeric components. Packaging now domi-nates the plastics industries. Out of 71 billion pounds of plastic use in differ-ent areas like building products, consumer products, and transportation, themaximum share (27.3%) goes to packaging. Petroleum-based nonbiodegrad-able plastic bags have already been restricted in Germany, Ireland, SouthAfrica, and Taiwan due to concerns about their disposability.

1.5.4 Biobased Polymeric Materials from Mixed Resources (Renewableand Petroleum Resources)

In day-to-day life most people are interested in using green materials but donot want to spend more money or use materials having inferior performancethan the existing dominant fossil fuel-based polymers and materials.Currently it is difficult to replace petroleum-based materials, from a cost andperformance perspective. It is not necessary to make a 100% substitution forpetroleum-based materials immediately. A viable solution is to combine thedifferent features and benefits of both petroleum and bioresources to pro-duce a useful product having the requisite cost-performance properties forreal-world applications. Biobased products may be categorized as follows:

(a) Low biobased content product (20% or less biobased content)(b) Medium biobased content product (2150% biobased content)(c) High biobased content product (5190% biobased content)


Some examples of biobased polymeric materials are the following:Biobased Sorona: DuPont Sorona polymer e.g., poly(trimethylene

terephthalate), PTT, a 3-carbon glycol terephthalate (3GT), is an example ofa condensation polymer that can be made from 1,3-propanediol (derivedfrom renewable corn sugar) and petroleum-derived terephthalic acid (TPA).DuPont received the 2003 Presidential Green Chemistry Award for the suc-cessful development of 1,3-propanediol (PDO) by a biological process. Moredetails on Sorona polymer can be found in Chapter 15.

Biobased thermoset resins: Petroleum-derived epoxy resins can beblended with epoxidized vegetable oil in the presence of suitable curingagents to make biobased epoxies.75,76 Petroleum-based epoxy resins areknown for their superior tensile strength, high stiffness, and exceptional

Wood 5.7%

Rubber,leather &textiles

7.1%

Metal 7.9%

Paper35.7%

Other 3.4%

Food scrapsYard trimmings

Plastics11.1%

Glass 5.5%

12.2% 11.4%

FIGURE 1.122001 total municipal solid waste (MSW) generation, 229 million tons (before recycling). (Adaptedfrom Municipal Solid Waste in the United States: 2001, U.S. Environmental Protection Agency.)

Transportation5%

Consumer &institutional

14%

Electrical3%

Building &construction

17%Furniture4%

All other14%

Industrial/machinery

1%

Exports12%

Adhesives/coatings2%

Packaging28%

FIGURE 1.13Packaging dominates plastic use: 2002 U.S. plastic use areas. Total 86.7 billion lb. (Adapted from American Plastic Council 2002.)


solvent resistance. One of the chief drawbacks of such epoxies is their brit-tleness or very low impact strength. However, the petroleum-based epoxiescan show improvement of impact strength when blended with epoxidizedvegetable oil, with a reduction in stiffness.76 A balance of stiffness and tough-ness can be obtained by adjusting the amount of epoxidized vegetable oiland petroleum-based epoxy in the resulting biobased epoxy. The biobasedresins are formed by blending ortho unsaturated polyester resins with func-tionalized vegetable oils; such bioresins on reinforcement with natural fibersmake a biobased composite material.14 Using bioresins as polymer matricescan improve the impact strength of the resulting biobased resin and can pro-duce a material with higher biobased content.

1.6 Biocomposites as Alternatives to Petroleum-BasedComposites: Recent Trends and Opportunities for the Future

Fiber-reinforced plastic composites began with cellulose fiber-reinforcedphenolics in 1908, later extending to urea and melamine, and reaching com-modity status in the 1940s with glass fiber-reinforced unsaturated poly-esters. The manufacture, use, and removal of traditional compositestructures, usually made of glass, carbon, or aramid fibers reinforced withepoxy, unsaturated polyester resins, polyurethanes, or phenolics, is beingscrutinized from an environmental and legislative perspective.3 The disposalof composites after their intended life span is becoming critical and expen-sive. The recycling as well as reuse of composite materials is not easy sincethey are made from two dissimilar materials; however, we find continuedefforts of such practice. Two disposal alternatives are land filling and

Metal: 16%

Paper: 10%

Plastics: 26%

Paperboard/molded pulp: 39%Metal: 16%

Paper: 10%

Glass: 4%

Wood: 4%

Textile: 1%

FIGURE 1.14U.S. packaging materials consumption, forecast (year 2005), excluding fast-food packaging,plastic food and garbage bags, tubes and cores, reconditioned barrels and drums, gas cylinders,and bulk containers. (Adapted from Plast. News, Sept. 9, 2002.)


incineration. Landfill space is decreasing due to heavy ongoing waste dis-posal. In the United States, the number of landfills dropped from 8000 to2314 between 1988 and 1998.77 Reports suggest that five states have less than5 years of landfill capacity; close behind are 14 more states with 5 to 10 yearsof landfill capacity.78

Biocomposites consist of reinforcing biofibers and matrix polymer sys-tems. Since the biofiber is biodegradable and traditional thermoplastics (likepolypropylene) and thermosets (like unsaturated polyester) are non-biodegradable, biocomposites from such fiber-reinforced polymers are clas-sified as the partially biodegradable type. If the matrix resin/polymer isbiodegradable, the biofiber-reinforced biopolymer composites would comeunder the completely biodegradable category, as represented in Figure 1.2.Two or more biofibers in combination with a polymer matrix result inhybrid biocomposites. The purpose of hybrid composites is the manipula-tion of properties of the resulting biocomposites.

The interrelationship between the development and applications of bio-composite materials is schematically represented in Figure 1.15. Some of thegrowing areas of applications for green/biocomposite materials are inautomotive parts, housing products, and packaging. The challenge in replac-ing conventional glass-reinforced plastics with biocomposites is to design

Expanding bio-compositematerials

complexity

Performance

Interface chemistry

Processingsynthesis

Energy/environment

Civilinfrastructure

(green housing)

Information/communication

PackagingValue-addedagriculturalproducts

Substitute ofpetroleum-

based materials

Transportation(auto parts)

Structurecomposition Value-added

forestproducts

FIGURE 1.15Biocomposite materials limits/complexity, interface chemistry, processing, structure/composition, and performance are to be governed to exploit their uses via value-added forest and agricultural products for various applications in transportation, packaging, green housing panels, etc., from energy/environmentally beneficial perspectives throughuniversity-industrial interactions, thus creating effective communication that would enablereal-world use of biocomposite materials.


materials that exhibit structural and functional stability during storage anduse, yet are susceptible to microbial and environmental degradation upondisposal without any adverse environmental impact.

Automakers will see potential in biocomposites7983 if these materials candeliver the same performance as conventional composites with lowerweight. Moreover, they exhibit nonbrittle fracture on impact, which isanother important requirement. In the United States, 10 million to 11 millionvehicles reach the end of their useful lives annually. A network of salvageand shredder facilities processes about 96% of these old cars. About 25 wt%of these vehicles, including plastics, fibers, foams, glass, and rubber, remainas waste. The car parts made from green composites would simply be buriedafter their lifetime and would in time be consumed naturally by bacteria.

The use of biocomposites in making interior automotive parts with natu-ral fiberpolypropylene and exterior parts from natural fiber polyester resin-based composites has been reported.80 Johnson Controls has startedproduction81 of door-trim panels from natural fiber and polypropylene. It isestimated that ~75% of a vehicles energy consumption is directly related tofactors associated with the vehicles weight, resulting in a critical need toproduce safe and cost-effective lightweight vehicles. Auto companies areseeking materials with sound abatement capability as well as reducedweight for fuel efficiency. Natural fibers possess excellent sound-absorbingefficiency and have excellent energy management characteristics. In auto-motive parts, compared to glass composites, the composites made from nat-ural fibers reduce the mass of the component and lower the energy neededfor production82 by 80%. Table 1.2 (after ref. 84) demonstrates how theweight of materials can be lowered by going from steel to glass fiber-reinforcedplastic (GFRP). Natural fiber composites can reduce the mass in a properlydesigned component. Chapter 7 provides a more detailed description of cur-rent trends of natural fiber composites in automotive applications.

Ford has a long history of R&D on new materials.83 Henry Ford beganexperimenting with composites around 1941, initially using compressed

TABLE 1.2

Weight Savings of Materials

Lightweight Material Percent Reduction Relative Cost

Material Replaced of Mass per Part*

High-strength steel Mild steel 10 1Aluminum Steel, cast iron 4060 1.32Magnesium Steel or cast iron 6075 1.52.5Magnesium Aluminum 2535 11.5Glass fiber- Steel 2535 11.5

reinforcedcomposites

* Cost includes both materials and manufacturing.

Source: Adapted from Powers, W.F., Adv. Mater. Process, 3841, 2000.


soybeans to produce composite plastic-like components. During that periodpetroleum-based chemicals were very inexpensive, so soy-based plastic didnot grow in importance. New environmental regulations and depletion ofand uncertainty about petroleum resources have revived interest in com-posite materials from soybean-based plastics and natural fibers. NorthAmerican market studies identify the potential impact and opportunities fornatural fiber composites.85 In the year 2000, the North American market fornatural fiber composites exceeded $150 million, By 2005, this market isexpected to reach nearly $1.4 billion in sales. The future of biobased com-posite materials for building product applications is bright (Table 1.3, afterref. 86), and several new natural fiber-based building materials are alreadymaking their way into the building industry. The majority of resins used inthe composite industry are thermosets.87 About 65% of all composites pro-duced currently for various applications use glass fiber and polyester orvinyl ester resins. Unsaturated polyester (USP) resins are widely used,thanks to a relatively low price, ease of handling, and a good balance ofmechanical, electrical, and chemical properties. Natural fiber-thermoset-based biocomposites are discussed extensively in Chapters 8 and 9.

Although natural fiber-reinforced nonbiodegradable polymer-basedcomposites are gaining interest, the challenge is to replace conventional glass-reinforced plastics with biocomposites that exhibit structural and functionalstability during storage and use, yet are susceptible to microbial and envi-ronmental degradation upon disposal without any adverse environmentalimpact. A three-cornered approach in designing biocomposites of superiorand desired properties include efficient but low-cost natural and biofibertreatment, matrix modification through functionalization and blending, andselection of appropriate and efficient processing techniques (Figure 1.16).

Since the significant attraction of natural fibers is their low cost, inexpen-sive yet effective surface treatments that avoid organic solvents are logicalways of making a reactive natural fiber surface.4,88 Aqueous silane solutionand a water emulsion of maleated polypropylene can be mixed together toproduce a novel sizing for natural fibers and thus make polypropylene-basedbiocomposites of superior mechanical properties.89 Through utilization of an

TABLE 1.3

North American Market Forecast for NWFCs

Market Year 2002 Year 2005 Year 2010

Building products 1062 2324 3375Infrastructure 126 163 185Transportation 63 78 88Consumer 32 56 89Industrial 28 45 61Total 1311 2667 3799

Source: Adapted from Principia Partners, Exton, Pennsylvania,

USA. With permission.


engineered natural fibers concept (Figure 1.17), superior strength biocom-posites can be obtained.90 This concept is defined as a suitable blend of sur-face-treated bast fibers (e.g., kenaf and hemp) and leaf fibers (e.g., henequen,sisal, and pineapple leaf fiber). Selection of blends of biofibers is also basedon the fact that the correct blend achieves an optimum balance in mechani-cal properties. The kenaf- or hemp/flax-based composites exhibit excellenttensile and flexural properties, while leaf fiber-based composites give better

Extrusion

CompressionMolding

InjectionMolding

Polymer matrixmodification

Reactiveblending

Maleatedmatrix as:

compatibilizer

efficient surfacetreatments ofnatural fibers

Water emulsion-based (silane+

maleated couplingagent) sizing

Silanetreatment

Alkalitreatment

SYNERGISM

Efficientbiocompositeprocessing

Extrusion

Compressionmolding

Injectionmolding

Biocompositestampable

sheet process

Polymer matrixmodification

Reactiveblending

Maleatedmatrix as

compatibilizer

efficient surfacetreatments ofnatural fibers

Water emulsion-based (silane+


Silanetreatment

Alkalitreatment

Low-cost butefficient surface

treatments ofnatural fibers

Water emulsion-based (silane +


Silanetreatment

Alkalitreatment

SYNERGISM

High-performancebiocompositeformulation

FIGURE 1.16Tricorner coordinate approach in designing and engineering of high-performance biocomposites.

Bast

f iber

s Kenaf

Sisal

Lea

f fib

ers

Flax

Henequen

Low

-cos

t but

effi

cient

sur

face

trea

tmen

t

Nat

ural

/bio

fiber

s

Bast

f iber

s Kenaf

Sisal

Lea

f fib

ers

Flax

Henequen

Different ratiosblends of desired bast

and leaf fibers aremixed, in a specificcase, 1:1 blend of

chopped kenaf andhenequen fiber may

be chosen.

"Engineerednatural/biofibers"

ready forbiocompositefabrications

FIGURE 1.17Concept on design of engineered natural fiber for biocomposite formulations.


impact properties to the composites. The combination of bast and leaf fiberis expected to provide a stiffness-toughness balance in the resulting bio-composites.

A strong fiber-matrix interface bond is critical for high mechanical prop-erties of the composites. In polymer matrix composites, there appears to bean optimum level of fiber-matrix adhesion, which can provide the best com-posite properties. Chapter 6 highlights this important aspect. Since naturalfibers are inexpensive, one should approach making a reactive surface ofnatural fibers through a low-cost but effective surface treatment and/or byusing a compatibilizer during biocomposite fabrication.91 Alkali treatment isan effective method to improve fiber-matrix adhesion in natural fiber com-posites.60,9294 It is believed that alkali treatment leads to fiber fibrillation, i.e.,the breaking down of fibers into smaller thin fibrils, thereby increasing theeffective surface area for contact with the matrix resin. Maleated polypropy-lene (MAPP) has received widespread application as a coupling agent or acompatibilizer in natural fiber-reinforced polypropylene composites.9598

Maleated polyethylene (MAPE) is used as a compatibilizer for natural fiber-polyethylene composites. The molecular weight and acid number of suchmaleated coupling agents affect the compatibilization chemistry. Maleatedpolyolefins of varying molecular weights and acid numbers are now com-mercially available.

There are two ways by which the maleic anhydride compabilizationchemistry can be implemented during biocomposite fabrication: First, natu-ral fibers are pretreated with maleated polymer and the treated fibers arethen dispersed into the desired polymer matrix during melt processing toobtain the biocomposites. The maleated coupling agent needs to be dis-solved in an appropriate concentration of specific organic solvents for fibertreatment. Such processes are not economical and also add volatile organiccompounds (VOCs) to the atmosphere. Second, in a reactive extrusionprocess one can add chopped biofiber, polymer matrix, and maleated cou-pling agent in one step, processing them into compatibilized biocompositepellets for further compression/injection molding. Such processing tech-niques are of commercial importance. In making compatibilized green com-posites from natural fibers and biopolymers like PLA and PHB, maleatedcompatibilizers (with appropriate molecular weight and acid number) arebeing developed at the laboratory scale but are not yet commercialized. Intime, with the widespread use of green composites, it is expected that com-mercial maleated biopolymers will be available.

In an industrial process, reducing the number of processing steps reducesthe overall cost of the product. Biopolymers like PHAs and PLA are plasti-cized with citrate or a combination of citrate and functionalized vegetableoil. The commercial polyhydroxybutyrate (PHB) from Biomer is plasticizedwith a proprietary citrate plasticizer system. On the industrial scale one cantarget doing the plasticization of the biopolymer along with natural fiberreinforcement in the presence of a compatibilizer in a one-step process(Figure 1.18) to make it more commercially attractive.


1.7 Sustainable Biobased Products: New Materials for a NewEconomy

The most common definition of sustainable is the following: sustainabledevelopment meets the needs of the present without compromising theneeds of future generations. The sustainability issues of bioplastics, e.g.,polylactic acid (PLA), polyhydroxyalkanoate (bacterial polyesters), and cel-lulosic plastics (cellulose esters), are the subject of scientific and engineeringstudies and divergent views.99105 The evaluation of a bioplastic or biocom-posite products sustainability is a complex problem. Life cycle assessment(LCA) analysis is a framework being developed that incorporates severalparameters to be considered, including the raw materials from which thebioplastic is generated, the energy consumed during bioplastic conversion,and its ultimate disposal or recycle. While comparing the sustainability of anewly emerging bioplastic with a petroleum-based plastic, considerationshould also be given to the technology development time gap betweenpetrochemicals (~100 years old) and developing bioplastics (~5 to 10 yearsold). Detailed descriptions of each of these factors are beyond the scope of

PHA/PLA + maleatedcompatibilizer

Addition of choppedengineered biofiber

K-Tron T-20feeder

Liquid plasticizer

Green composite pelletsfor further processing

Twin screw extruder

Pelletizer

Peristaltic pump

FIGURE 1.18Schematic representation in fabricating bio/green composite pellets through reactive extrusionprocessing.


this chapter, but the interested reader can find contemporary references onthe subject.

It is encouraging to derive cost-effective biobased products or biocompos-ites from inexpensive bioplastics through inexpensive natural and biofiberreinforcements. Although most bioplastics cannot compete economically intheir present state with petroleum-based plastic, cost-effective biocompositeformulations and designs with natural fiber reinforcements can compete at theeconomic level. The emergence of new applications of biocomposites will spurlarge-scale demand for bioplastics, which would help the long-range attain-ment of sustainability. A detailed understanding of natural and biofibers, bio-plastics, and their biocomposite formulations will be the foundation fordeveloping new and emerging biobased composite materials. Sustainabilityissues of biopolymers and biobased products are discussed in Chapter 27.

Since natural fibers are inexpensive reinforcements for use with biopoly-mers, their use would be to provide new biobased and green materials thatcan attain sustainability. Green composite formulations incorporating5060% inexpensive natural fiber are expected to be cost-effective, withadditional environmental benefits. A biobased product derived from renew-able resources that can have the attractive attributes of recyclability, trig-gered biodegradability (i.e., stable in use but biodegradable after disposal),along with commercial viability and environmental acceptability is a sus-tainable biobased product (schematic representation is given in Figure 1.19).An additional benefit is that eventual decomposition of the biocompositedoes not add any new net CO2 to the global environment, since the compo-nents came from plant material (overall balance; see Figure 1.8).

Product realization of green/biobased/natural fiber composite materialsrequires a complete LCA. The glass fiber-reinforced plastics (GFRP) are thepredominant composites in our industries today. The natural fiber compositeshave the potential to replace GFRP in many applications. A simplified LCAstudy approach of green composites vs. traditional glass fiber composites isshown schematically in Figure 1.20. LCA studies comparing natural fibercomposites and glass fiber composites have recently been reviewed.102 The

Renewable/biobased

Recyclable/natural

recycling

Sustainable

Triggeredbiodegradable

Commercial viability&

environmental acceptibility

FIGURE 1.19One concept of sustainable biobased product that can fit well to green composites.


discussion of this review centers mostly on composites from glass and naturalfibers using traditional plastics like polypropylene and ethylene propylenediene (EPDM), especially for automotive applications. Natural fiber compos-ites are likely to be environmentally superior to GFRP. Some of the importantreasons are the following. (1) the production of natural fiber poses lower envi-ronmental impact compared to glass fiber production; (2) natural fiber-tradi-tional plastic composites can have higher biofiber content for equivalentperformance of a GFRP, thus reducing more polluting base polymer content,and (3) natural fiber composites can provide lighter weight as compared toGFRP, which, for automotive parts use, can improve fuel efficiency.

1.8 Conclusions

New environmental regulations and societal concerns have triggered thesearch for new materials, products, and processes that are compatible with

bioplasticglass fiber &

traditional plastic

Cropproduction

Compositepart use

composite partmanufacture

Bioplasticmanufacture

Fiberextraction

End of lifemanagement

(recycling, disposal)

Petroleumextraction

Compositepart use

Glass fiberplasticcomposite part

manufacture

Plasticmanufacture

Refining

End of life management

(recycling, disposal)

Glassfiber

manufacture

natural fiber &

Green

Conventionalcomposites from

Greencomposites from

FIGURE 1.20Simplified LCA study approach for green composites vs. glass fiber-reinforced composites.


the environment. The incorporation of bioresources into the materials, prod-ucts, and processes of today can satisfy these concerns and reduce furtherdependency on petroleum reserves. Biocomposites can supplement andeventually replace petroleum-based composite materials in several applica-tions, thus offering new agricultural, environmental, manufacturing, andconsumer benefits. Several critical issues related to biofiber surface treat-ment to make it more reactive, bioplastic modification to make it a suitablematrix for composite application, and processing techniques depending onthe type of fiber form (chopped, nonwoven/woven fabrics, yarn, sliver, etc.),need to be solved to design biocomposites of commercial interest. Recentadvances in genetic engineering, natural fiber development, and compositescience offer significant opportunities for improved value-added materialsfrom renewable resources with enhanced support for global sustainability.Thus, the main motivation for developing biocomposites has been and stillis to create a new generation of fiber-reinforced plastics competitive withglass fiber-reinforced composites but which are environmentally compatiblein terms of production, use, and removal. Natural fibers are biodegradableand renewable resource-based bioplastics can be designed to be eitherbiodegradable or not, according to the specific demands of a given applica-tion. Bioplastics and biocomposites based on renewable agricultural and bio-mass feedstocks can form the basis for a portfolio for sustainable andecoefficient biobased products that can compete and capture markets cur-rently dominated by products based exclusively on petroleum feedstocks.There is an immense opportunity in developing new biobased products, butthe real challenge is to design sustainable biobased products through inno-vative ideas. Green materials are the wave of the future.

Acknowledgments

We acknowledge NSF/EPA (Award #DMI-0124789) under the 2001Technology for a Sustainable Environment (TSE) Program, EPASTARaward #RD-83090401 under the 2002 Environmental Futures Research inNanoscale Science Engineering and Technology, and NSF 2002 Award#DMR-021686, NSF- PREMISE (Product Realization and EnvironmentalManufacturing Innovative System) 2002 Award #0225925, , NSF-NER 2002Award #BES- 0210681 under the Nanoscale Science and Engineering (NSE);Nanoscale Exploratory Research (NER) Program, NSF-Partnership forAdvancing Technology in Housing (PATH) 2001 Award #0122108, NSF 2002Award #DMR-0216865, under the Instrumentation for Materials Research(IMR) Program, USDA-NRI (Grant No. 2001-35504-10734) and GREEEN(Generating Research and Extension to meet Economic and EnvironmentalNeeds) (Grant Nos. GR01-037 and GR02-066), USDA-MBI Award No. 2002-34189-12748-S4057 for the project Bioprocessing for Utilization of


Agricultural Resources and Michigan State Universitys start-up fundingto A.K. Mohanty.

References

1. Wedin, R., Chemistry on a High-Carb Diet, American Chemical Society,Washington, D.C. 2004, pp. 3035.

2. Gross, R.A. and Karla, B., Biodegradable polymers for environment, Science,297, 803807, 2002.

3. Mohanty, A.K., Misra, M., and Hinrichsen, G., Biofibers, biodegradable poly-mers and biocomposites: an overview, Macromol. Mater. Eng., 276/277, 125,2000.

4. Mohanty, A.K., Misra, M., and Drzal, L.T., Sustainable Bio-Composites FromRenewable Resources: Opportunities and Challenges in the Green MaterialsWorld, J. Polym. Environ., 10, 1926, 2002.

5. Netravali, A.N. and Chabba, S., Composites get greener, Mater. Today, April2003, pp. 2229.

6. Plant/Crop-based Renewable Resources 2020, URL: http://www.oit.doe.gov/agriculture/pdfs/vision2020.pdf.

7. The Technology Roadmap for Plant/Crop-based Renewable Resources 2020,URL: http://www.oit.doe.gov/agriculture/pdfs/ag25942.pdf.

8. Drumright, R.E., Gruber, P.R., and Henton, D.E., Polylactic acid technology,Adv. Mater., 12, 18411846, 2000.

9. Petrovic, Z., Guo, A., and Javani, I., Process for the Preparation of Vegetable OilBased Polyols and Electroninsulating Casting Compounds Created fromVegetable Oil Based Polyols, U.S. Patent 6,107,433, 2000.

10. Thomas, S.M., Biomass Grass makes for composite Cars, Mater. World, 9, 24,2001.

11. Berenberg, B., Natural Fibers and Resins Turn Composites Green, Compos.Technol., 13, 2001.

12. Mapleston, P., Automakers see strong promise in natural fiber reinforcements(thermoplastic reinforced with natural fiber), Modern Plast., 76, 7374, 1999.

13. Mohanty, A.K., Wibowo, A., Misra, M., and Drzal, L.T., Effect of ProcessEngineering on the Performance of Natural Fiber Reinforced Cellulose AcetateBiocomposites, Compos. Part A: Appl. Sci. Manufac., 35, 363370, 2004.

14. Mehta, G., Mohanty, A.K., Misra, M., and Drzal, L.T., Biobased resin as a tough-ening agent for biocomposites, Green Chem., 6, 254258, 2004.

15. Thayer, A.M., Living and Loving Life Sciences, Chem. Eng. News, 76, Nov. 23,1998, pp. 1724.

16. Thayer, A.M., Chasing the Innovation Wave, Chem. Eng. News, 77, Feb. 8, 1999,pp. 1722.

17. Gutowski, T.G., Murphy, C.F., Allen, D.T., Bauer, D.J., Bras, B., Piwonka, T.S.,Sheng, P.S., Sutherland, J.W., Thurston, D.L., and Wolf, E.E., WTEC Panel Reporton Environmentally Benign Manufacturing, NSF-DOE Report, April 2001.

18. Fiber reinforced plastics use, Plast. News, August 2002.19. Barghoorn, P., Stebani, U., and Balsam, M., Trends in Polymer Chemistry 1997.

Part 2: Applied Polymer Chemistry, Acta Polymerica, 49, 266267, 1998.


20. Thomas, S.M., Biomass Grass makes for composite Cars, Mater. World, 9, 24, 2001.21. Liu, W., Mohanty, A.K., Drzal, L.T., Askeland, P., and Misra, M., Effect of alkali

treatment on the structure, morphology and thermal properties of native grassfibers as reinforcements for polymer matrix composites, J. Mater. Sci., 39,10511054, 2004.

22. Huda, M.S., Mohanty, A.K., Drzal, L.T., Misra, M., and Schut, E., Physico-mechanical Properties of "Green" composites from Poly(lactic acid) andCellulose Fiber, Proceedings of the 10th Annual Global Plastics EnvironmentalConference (GPEC 2004), Feb. 18 and 19, 2004, Detroit, MI, Paper # 11.

23. Mohanty, A.K., Drzal, L.T., Ferguson, K.J., Dale, B.E., Misra, M., and Schalek, R.,Explosion Treatment of Corn Stalk Fibers and Their Characterizations: A NewLook At Value Added Applications, Polym. PreprintPolym. Chem. Div., Am.Chem. Soc., 43, 749750, 2002.

24. Selke, S.E. and Wichman, I., Woodfiber/polyolefin composites, Compos. Part A:Appl. Sci. Manufac., 35, 321326, 2004.

25. Smith, P., Proceedings of the 6th International Conference on WoodfiberPlasticComposites, Forest Products Society, Madison, WI, May 2001, pp. 1317.

26. Harper, D. and Wolcott, M.P., Wolcott, "Interaction between coupling agentsand lubricants in wood-polypropylene composites, Compos. Part A: Appl. Sci.Manufac., 35, 385394, 2004.

27. Rouchi, A.M., Lignin and Lignan Biosynthesis, Chem. Eng. News, 78, 2000, pp.2932.

28. Narayan, R., Commercialization technology: a case study of starch basedbiodegradable plastics, in Paradigm for Successful Utilization of Renewable Resources,Sessa, D.J. and Willett, J.L., Eds., AOCS Press, Champaign, IL, 1998, p. 78.

29. Hocking, P.J., The classification, preparation, and utility of degradable, J.Macromol. Sci. Rev. Macromol. Chem. Phys., C32, 3554, 1992.

30. Wilkinson, S.L., Nature`s Pantry is open for business, Chem. Eng. News, Jan. 22,2001, pp. 6162.

31. Misra, M., Mohanty, A.K., and Drzal, L.T., Environmentally-FriendlyComposites from Jute and Mater-Bi, SAMPE, Society for the Advancement ofMaterial and Process Engineering, Dearborn, MI, USA, Sept. 1214, 2000. Fullpaper published in the Proceedings, 2000, pp. 189196.

32. Mohanty, A.K., Wibowo, A., Misra, M., and Drzal, L.T., Effect of ProcessEngineering on the Performance of Natural Fiber Reinforced Cellulose AcetateBiocomposites, Compos. Part A: Appl. Sci. Manufac., 35, 363370, 2004.

33. Wibowo, A.C., Mohanty, A.K., Misra, M., and Drzal, L.T., Chopped IndustrialHemp Fiber Reinforced Cellulosic Plastic Bio-composites: Thermo-Mechanicaland Morphological Characterization, Ind. Eng. Chem. Res., 43, 48834888, 2004.

34. John, J. and Bhattacharya, M., Properties of reactively blended soy protein andmodified polyesters, Polym. Int., 48, 11651172, 1999.

35. Williams, G.I. and Wool, R.P., Composites from natural fibers and soy oil resins,Appl. Compos. Mater., 7, 421432, 2000.

36. Liu, W., Mohanty, A.K., Misra, M., and Drzal, L.T., Injection molded Greencomposites from native grass and soy based bioplastic, American Society forComposites (18th Annual Technical Conference), Oct. 1922, 2003, Gainesville, FL(Full Paper Published: Proceedings of the American Society for Composites 2003,Sankar, B.V., Ifju, P.G., and Gates, T.S., Eds.)

37. Tummala, P., Mohanty, A.K., Misra, M., and Drzal, L.T., Eco-compositeMaterials from Novel Soyprotein-Based Bioplastics and Natural Fibers,


Proceedings of the 14th International Conference on Composite Materials (ICCM14),San Diego, CA, USA, July 1418, 2003 (Full paper published in the ICCM14Conference Proceedings, #1759).

38. Lodha, P. and Netravali, A.N., Characterization of interfacial and mechanicalproperties of green composite with soy protein isolate and ramie fiber, J. Mat.Sci., 37, 36573665, 2002.

39. Leaversuch, R., Biodegaradable polyester: packaging goes green, Plast. Technol.,48, p. 66, 2002.

40. Potts, J.E., Clendinning, R.A., Ackart, W.B., and Niegish, W.D., Biodegradabilityof synthetic polymers, Polym. Sci. Technol., 3, 61, 1973.

41. Averous, L., Moro, L., Dole, P., and Fringant, C., Properties of thermoplasticblends: starch-polycaprolactone, Polymer, 41, 41574167, 2000.

42. Kweon, D.K., Kawasaki, N., Nakayama, A., and Aiba, S., Preparation and char-acterization of starch/polycaprolactone blend, J. Appl. Polym. Sci., 92,17161723, 2004.

43. Nitz, H., Semke, H., Landers, R., and Mulhaupt, R., Reactive extrusion of poly-caprolactone compounds containing wood flour and lignin, J. Appl. Polym. Sci.,81, 19721984, 2001.

44. Marshall, D., Eur. Plast. News., Mar. 1998, p. 23.45. Carothers, W.H., Dorough, G.L., and Van Natta, F.J., Studies of polymerization

and ring formation. x. The reversible polymerization of six-membered cyclicesters, J. Am. Chem. Soc., 54, 761772, 1932.

46. Lowe, C.E., Preparation of High Molecular Weight Polyhydroxy Acetic Ester,U.S. Patent 2,668,162, 1954.

47. Lipinsky, E.S. and Sinclair, R.G., Is lactic acid a commodity chemical? Chem.Eng. Prog., 82, 2632, 1986.

48. Drumright, R.E., Gruber, P.R., and Henton, D.E., Polylactic acid technology,Adv. Mater. 12, 18411846, 2000.

49. Gruber, P.R., Hall, E.S., Kolstad, J.J., Iwen, M.L., Benson, R.D., and Borchardt,R.L., Continuous Process for Manufacture of Lactide Polymers with ControlledOptical Purity, U.S. Patent 5,142,023, 1992 (to Cargill).

50. Enomoto, K., Ajioka, M., and Yamaguchi, A., Polyhydroxycarboxylic Acid andPreparation Process Thereof, U.S. Patent 5,310,865, 1994 (to Mitsui Tuatsu).

51. Lanzillotta, C., Pipino, A., and Lips, D., New functional biopolymer naturalfiber composite from agricultural resources, ANTEC-2002, 2002.

52. Plackett, D., Andersen, T.L., Pedersen, W.B., and Nielsen, L., Biodegradable com-posites based on L-polylactide and jute fibres, Compos. Sci. Technol., 63, 1317, 2003.

53. Oksman, K., Skrivfars, M., and Selin, J.-F., Natural fibres as reinforcement inpolylactic acid (PLA) composites, Comp. Sci. Technol., 63, 1317, 2003.

54. Pool, R., In search of Plastic Potato, Science, 245, 1187, 1989.55. Hocking, P.J. and Marchessault, R.H., Chemistry and Technology of Biodegradable

Polymers, Blackie & Son, Glasgow, 1994, p. 48.56. Amass, W., Amass, A., and Tighe, B., A review of biodegradable polymers: uses,

current developments in the synthesis and characterization of biodegradablepolyesters, blends of biodegradable polymers and recent advances in biodegra-dation studies, Polym. Int., 17, 89, 1998.

57. Avella, M., Immirzi, B., Malinconico, M., Martuscelli, E., and Volpe, M.G.,Reactive blending methodologies for biopol, Polym. Int., 39, 191, 1996.

58. King, P.P., Biotechnology: an industrial view, J. Chem. Technol. Biotechnol., 32, 2,1982.


59. Fernandes, E.G., Pietrini, M., and Chiellini, E., Bio-based polymeric compositescomprising wood flour as filler, Biomacromolecules, 5, 12001205, 2004.

60. Mohanty, A.K., Khan, M.A., Sahoo, S., and Hinrichsen, G., Effect of chemicalmodification on the performance of biodegradable Jute yarnBiopol compos-ites, J. Mater. Sci., 35, 25892595, 2000.

61. Luo, S. and Netravali, A.N., Interfacial and mechanical properties of environ-ment -friendly "green" composites made from pineapple fibers andpoly(hydroxybutyrate-co-valerate) resin, J. Mater. Sci., 34, 37093719, 1999.

62. Grigat, G., Koch, R., and Timmermann, R., BAK 1095 and BAK 2195: completelybiodegradable synthetic thermoplastics, Polym. Degrad. Stab. 59, 223, 1998.

63. Polym. News, 23, 129, 1998.64. Marshall, D., Eur. Plast. News, Mar. 1998, p. 23.65. Frankfurter Allegemeine Zeitung, 24 Dec. 2001, p.19.66. http://www.basell.com/portal/site/basell/index.jsp67. Bastioli, C., Properties and applications of Mater-Bi starch-based materials,

Polym. Degradation Stab., 59, 263272, 1998.68. http://www.dow.com/webapps/lit/litorder.asp?filepath5tone/pdfs/noreg/

321-00052.pdf&pdf5true69. Grigat, E., Koch, R., and Timmermann, R., BAK 1095 and BAK 2195: completely

biodegradable synthetic thermoplastics, Polym. Degradation Stab., 59, 223226,1998.

70. http://www.eastman.com/Product_Information/ProductHome.asp?Product51469&familyGMN

71. Asrar, J. and Gruys, K.J., Biodegradable polymer (Biopol), Biopolymers, Doi,Yoshiharu, Steinbruchel, Alexander, Eds., 4, 5390, 2002.

72. Municipal Solid Waste in the United States: 2001 Facts and Figures ExecutiveSummary, U.S. Environmental Protection Agency, http://www.epa.gov/epaoswer/non-hw/muncpl/pubs/msw-sum01.pdf

73. American Plastic Council 2002 Percentage Distribution of Thermoplastic ResinSales & Captive use by Major Market. http://www.americanplasticscouncil.org/benefits/economic/PIPSmajmktchart_2002.pdf

74. Impact Marketing Consultants Inc. Manchester Center, VT; Plast. News, Sept. 9,2002.

75. Miyagawa, H., Mohanty, A.K., Misra, M., and Drzal, L.T., Thermo-physical andImpact Properties of Epoxy Containing Epoxidized Linseed Oil: Part 1:Anhydride-cured Epoxy, Macromol. Mater. Eng., 289, 629635, 2004.

76. Miyagawa, H., Mohanty, A.K., Misra, M., and Drzal, L.T., Thermo-physical andImpact Properties of Epoxy Containing Epoxidized Linseed Oil: Part 2: Amine-cured Epoxy, Macromol. Mater. Eng., 289, 636641, 2004.

77. Stevens, E.S., Green Plastics, Princeton University Press, Princeton, 2002.78. Mase, T., Drzal, L.T., and Jurek, B., Development of a Heat/Pressure Formable

Wood Fiber Thermoplastic Composite from Recycled Paperboard, Proceedings ofthe 8th Annual Global Plastics Environmental Conference, GPEC, SPEEnvironmental Division, 2002, pp. 245249.

79. Mapleston, P., Automakers see strong promise in natural fiber reinforcements(thermoplastic reinforced with natural fiber), Mod. Plast., pp. 7374, 1999.

80. Grown to Fit the Part, DaimlerChrysler High Tech. Report, 1999, pp. 8285.81. Green door-trim panels use PP and natural fibers, Plast. Technol., 46, 27, 2000.82. Broge, J.L., Natural fibers in automotive components, Automotive Eng. Int., 108,

120, 2000.


83. Brouwer, W.D., Natural Fibre Composites: Where Can Flax Compete WithGlass, SAMPE J., 36, 1823, 2000.

84. Powers, W.F., Automotive materials in the 21st century, Adv. Mater. Process, 157,3841, 2000.

85. Eckert, C. (Kline & Co, NJ), Opportunities for natural fiber in plastic compos-ites, Oct. 46, 2000, Memphis, TN, USA.

86. Personal correspondence with Jim Morton, Principia Partners, Exton,Pennsylvania, USA. The data and projections are based on multiclient reportand study released to industry in 2003.

87. Mohanty, A.K. and Misra, M., Studies on Jute CompositesA Literature Review,Polym.Plast. Technol. Eng., 34, 729792, 1995.

88. Drzal, L.T., Mohanty, A.K., and Misra, M., Environmentally Benign PowderImpregnation Processing and Role of Novel Water Based Coupling Agents inNatural Fiber-Reinforced Thermoplastic Composites, Polym. PreprintPolym.Chem. Div. Am. Chem. Soc., 42, 3132, 2001.

89. Mohanty, A.K., Drzal, L.T., and Misra, M., Novel Hybrid Coupling Agent asAdhesion Promoter in Natural Fiber Reinforced Powder PolypropyleneComposites, J. Mater. Sci. Lett., 21, 18851888, 2002.

90. Mohanty, A.K., Drzal, L.T., and Misra, M., Engineered Natural Fiber ReinforcedComposites: Influence of Surface Modifications and Novel PowderImpregnation Processing, J. Adhes. Sci. Technol., 16, 9991015, 2002.

91. Mohanty, A.K., Misra, M., and Drzal, L.T., Surface modifications of naturalfibers and performance of the resulting biocomposites: an overview, Compos.Interface, 8, 313343, 2001.

92. Bisanda, E.T.N. and Ansell, M.P., The effect of silane treatment on the mechan-ical and physical properties of sisal-epoxy composites, Compos. Sci. Technol., 41,165, 1991.

93. Gassan, J. and Bledzki, A.K., Possibilities for improving the mechanical proper-ties of jute/epoxy composites by alkali treatment of fibres, Compos. Sci. Technol.,59, 1301, 1999.

94. Prasad, S.V., Pavithran, C., and Rohatgi, P.K., Alkali treatment of coir fibers forcoir-polyester composites, J. Mater. Sci., 18, 1443, 1983.

95. Felix, J. and Gatenholm, P., The nature of adhesion in composites of modifiedcellulose fibers and polypropylene, J. Appl. Polym. Sci., 42, 609, 1991.

96. Gassan, J. and Bledzki, A.K., The influence of fiber-surface treatment on themechanical properties of jute-polypropylene composites, Compos. Part A: Appl.Sci. Manufac., 28A, 1001, 1997.

97. Sanadi, A.R., Caulfield, D.F., Jacobson, R.E., and Rowell, R.M., RenewableAgricultural Fibers as Reinforcing Fillers in Plastics: Mechanical Properties ofKenaf Fiber-Polypropylene Composites, Ind. Eng. Chem. Res., 34, 1889, 1995.

98. Keener, T.J., Stuart, R.K., and Brown, T.K., Maleated coupling agents for naturalfibre composites, Compos. Part A: Appl. Sci. Manufac., 35, 357362, 2004.

99. Gerngross, T.U. and Slater, S.C., How green are green plastics? Sci. Am., August2000, pp. 3741.

100. Scott, G. and Wiles, D.M., Programm

S2Biocomposite02_03_04th

Documents

biobased materials

petroleumbased composites

petroleum resources1

biobased polymeric materials

new materials

nonrenewable petroleum

biodegradable polymers

sustainable biobased