revisão bibiliográfica

Ttulo

THERMAL PROPERTIES OF POLY(LACTIC ACID)/ORGANO-MONTMORILLONITE NANOCOMPOSITES

Effect of expanded graphite/layered-silicate clay on thermal, mechanical and fire retardant properties of poly(lactic acid)

Mechanical performance of biocomposites based on PLA and PHBV reinforced with natural fibres A comparative study to PP

Polylactide/montmorillonite nanocomposites: Structure, dielectric, viscoelastic and thermal properties

Preparation and biodegradation of clay composites of PLA

Preparation and Characterization of Polylactic Acid/Polycaprolactone Clay Nanocomposites

Preparation and Properties of PolylactideSilica Nanocomposites

Processing and mechanical properties of natural fiber reinforced thermoplastic starch biocomposites

Rheology and thermal stability of polylactide/clay nanocomposites

Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

Processing of poly(lactic acid): Characterization of chemical structure, thermal stability and mechanical properties

Biodegradable self-reporting nanocomposite films of poly(lactic acid) nanoparticles engineered by layer-bylayer assembly

Biodegradable Polylactide/Montmorillonite Nanocomposites

Revista/Ano

Autores

Journal of Thermal Analysis and Calorimetry, Vol. 95 (2009) 2, 627632

W. S. Chow; S. K. Lok

Polymer Degradation and Stability 95 (2010) 1063-1076

Fukushima, K.; Murariu, M.; Camino, G.; Dubois, P.

Composites Science and Technology 70 (2010) 16871696

Bledzki, A. K.; Jaszkiewicz, A.

European Polymer Journal 43 (2007) 28192835

Pluta, M.; Jeszka, J. K.; Boiteux, G.

Reactive & Functional Polymers 69 (2009) 371379

Nieddu, E.; Mazzucco, L.; Gentile, P.; Benko, T.; Balbo, V.; Mandrile, R.; Ciardelli, G.

Journal of Applied Sciences, 10 (2): 97-106 (2010)

Hoidy, W.H.; M.B. Ahmad; E.A.J. AlMulla; N.A.B. Ibrahim

Published online 28 January 2010 in Wiley InterScience

Zhu, A. P.; Diao, H. X.; Rong, Q. P.; Cai, A. Y.

Journal of Thermoplastic Composite Materials 2007 20: 207

Torres, F. G.; Arroyo, O. H.; Gomez, C.

Polymer Degradation and Stability 91 (2006) 3149e3155

Wu, D. F.; Wu, L. A.; Wu, L. F.; Zhang, M.

Polymer Degradation and Stability 91 (2006) 2198e2204

Wu, T. M.; Wu, C. Y.

Polymer Degradation and Stability 95 (2010) 116e125

Carrasco, F.; Pages, P.; Gamez-Perez, J.; Santana, O. O.; Maspoch, M. L.

Polymer 51 (2010) 4127e4139

Orozco, V. H.; Kozlovskaya, V.; Kharlampieva, E.; Lopez, B. L.; Tsukruk, V. V.

Journal Nanosci Nanotechnol. 2003 Dec;3(6):503-10.

Ray S. S.; Yamada K.; Okamoto M.; Ueda K.

Palavras chave

Materiais

PLA; OMMT (Nanomer I.28E Nanoclay); maleic anhydride grafted EPMgMA, nanocomposites, organoethylene propylene rubber (EPMgMA); montmorillonite, poly(lactic acid), thermal single-screw extruder (Betol Machinery properties Ltd., England); compression molding (Gotech, Taiwan).

Poly(lactic acid); Expanded graphite; Clay; Nanocomposites; Biodegradable polymer

The poly(lactic acid) (PLA, 4032D) was a commercial grade supplied by NatureWorks LL

Poly-(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV); Polylactid 4042D (PLA); Polypropylene 575P (PP); Poly(butylene adipate-co-butylene A. Short-fibre composites, B. Mechanical terephthalate) (PBAT); Abaca; Jute; properties, B. Impact behaviour, Man-made cellulose; poly(butylene Biocomposites adipate-co-butylene terephthalate); maleic-acid anhydride; TP Licocene PP MA 6452

Polylactide; Nanocomposites; Compatibilization; Thermal properties; Viscoelastic properties; Dielectric properties

Polylactide (Cargill-Dow); Organically treated montmorillonite Cloisite_ 30B (Southern Clay Products (Gonzales, TX)); ExxelorTM VA1803 (ExxonMobil Chemical)

Polylactide, Nanocomposites, Degradation, Silicates, Blood plasma

Sepiolite CD1 (without organic modifier) (Tolsa); Bentone SD2 (montmorillonite with an aryl modifier) (Elementis); Somasif MEE (fluorohectorite with a dihydroxy organic modifier) (Unicoop); Nanofil 804 (montmorillonite with a dihydroxy organic modifier) (Sd Chemie); Cloisite 30B (montmorillonite with a dihydroxy organic modifier) (Southern Clay)

Polylactic acid, polycaprolactone, fatty hydrixamic acid, octadecylamine, nanocomposites, blending

Sodium montmorillonite (Kunimine Ind. Co. Japan); Hexane(T.J. Baker, USA (2009)); Octadecylamine (Acros Organics, USA); Polylactic acid (Japan); Polycaprolactone (Solvay Caprolactone, Warrington, England); Hydrochloric acid HCl (Sigma-Aldrich, Germany).

adhesion; composites; dispersions; nanocomposites

PLA (Biomer L9000 - Biomer, Inc. (Krailling, Germany); oleic acid (Shanghai Chemical Reagent Co., Ltd. Shanghai, China); Fumed silica (Nanjing University of Technology (Nanjing, China)

compression molding, starch polymers, natural fiber composites

starch; natural fibers (sisal, jute, cabuya); 3% non-ionic detergent; distilled water; potato, sweet potato, corn (maize) starch; plasticizers (ethylene glycol, glycerol, propylene glycol, chitosan, and water in concentrations between 0 and 10%)

Polylactide; Clay; Nanocomposites; Rheology; Thermal stability

Poly(butylenes terephthalate) (PLA, 3051D - NatureWorks Co. Ltd., USA); organoclay (DK2 - Fenghong Clay Co. Ltd., PR China); methyl tallow bis(2hydroxyethyl) ammonium;

natural sodium montmorillonite with a trioctahedral smectite structure and a cation exchange capacity; poly(lactic Poly(lactic acid); Nanocomposite; acid) (Wei Mon Industry Co., LTD Chitosan; Dynamic mechanical property; (Taipei, Taiwan)); Na+ in layered silicate Biodegradability galleries; n-hexadecyl trimethylammonium bromide; chitosan; methylene chloride solution; deionized water.

Poly(lactic acid) polymer 2002D Poly(lactic acid), Injection, Extrusion, (Natureworks - Nupik International Crystallinity, Degradation, Tensile testing (Poliny, Spain); 1,1,1,3,3,3-hexafluoro2-propanol ; sodium trifluoroacetate.

The poly-(D,L-lactic acid) (PLA Mn 136,000) - Jamplast Inc (Ellisville, USA); PAA (Mw 90,000); PVPON (Mw 55,000); poly(ethylene imine) (PEIMw 70,000, 30% aqueous solution); monoBiodegradable, Layer-by-layer composite and dibasic sodium phosphate; 1-ethylfilms, Poly(D,L-lactic acid) particles 3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC); ethylene diamine (EDA); HAuCl4 solution; acetone; 0.1 M borate buffers (pH 10); silica microspheres; silicon wafers; quartz slides

PLA with D content of 1.11.7% (supplied by Unitika Co. Ltd., Japan); Polylactide, Montmorillonite, organically modified montmorillonite Nanocomposite, Crystallization, Materials (Hojun Yoka Co., Japan) (synthesized Properties by replacing Na+ in montmorillonite with dimethyldioctadecylammonium cation by ion exchange reaction).

Tcnicas

X-ray diffraction (XRD); Differential scanning calorimetry (DSC); Thermogravimetry analysis (TG);

Brabender 50 EHT; Agila PE20 hydraulic press; DSM MicroInjection Moulding Machine; Wide Angle X-Ray Scattering Analysis (Siemens D5000 diffractometer); Transmission Electron Microscopy (PhilipsCM100; Reichert Jung Ultracut 3E FC4E ultracryomicrotome); Differential Scanning Calorimetry (Q200 -TA Instruments - Differential Scanning Calorimeter); Thermogravimetric Analysis (TGA Q500-TA Instruments); Tensile testing measurements (Lloyd LR 10K; ASTM D638-02a); Notched impact strength measurements (IZOD RAYRAN 2500; ASTM D256); Horizontal burning test (UL94 HB - ASTM D635 and ISO 1210); Vertical burning test (UL94 V - ASTM D3801 and ISO 1210);

extruder; Zwick/Roell UPM 1446 universal testing machine; Anotch Charpy impact strength (machine NOTCHVIS by CEAST); scanning electron microscopy (SEM)(Cam-Scan MV 2300); Keyence VHX-600K microscope (VHX analysis software)

counterrotating internal mixer (Brabender OHG, Duisburg, Germany); size exclusion chromatography (SEC) method in methylene chloride; X-ray diffraction (XRD); rheometer (ARES; Rheometric Scientific); Thermal properties - DSC 2920, TA Instruments; Dynamic mechanical properties - MkIII DMTA apparatus (Rheometric Scientific, Inc.); Novocontrol Concept 40 a-analyzer interfaced to the sample by a broadband dielectric converter (BDC, Novocontrol); lock-in amplifier (Stanford Research 810).

Brabender counter-rotating internal mixer W50E; XRDanalyses (Thermo ARL diffractometer X-tra 48 using Cu Ka Xray source); Scanning electron microscopy (LEO 1450 VP instrument); Differential scanning calorimetry (TA Q1000 instrument); Thermogravimetry (TA Q 500 instrument); Transmission FTIR spectra (PerkinElmer Spectrum GXIII spectrophotometer); Tensile test (MTS Qtest Elite 10, MTS Systems Corporation, Eden Prairie, MN); Laboratory Press Gibitre; Hydraulic Press Specac; incubator; enzymatic colorimetric assay (Advia Chemistry Systems Bayer Germany); Size Esclusion Chromatography (Waters HPLC Pump515 instrument, Waters R401 differential refractometer); Polymer Labs Caliber software (Polymer Laboratories) Synthesis of (FHAs); Preparation of organoclay; Preparation of PLA/PCL-clay nanocomposites, by solution casting (Ultra Sonic Cathode); Preparations of PLA/PCL-clay nanocomposites by melt blending (internal mixer - Haake Polydrive); Characterization (KBr disk method (Perkin Elmer FTIR 1650 spectrophotometer); Elemental analyser (LECO CHNS-932); X-ray Diffraction (shimadzu XRD 6000 diffractometer); TG analysis (Perkin Elmer model TGA 7 Thermogravimetric analyzer); SEM (JEOL attached with Oxford Inca Energy 300 EDXFEL scanning electron microscope)

Modification of the nanosilica by OA (ultrasound bath; magnetic stirrer; centrifugal); Preparation of the sheets (Carver laboratory press - model 3925 hydraulic unit, Carver, Inc., Wabash, IN); Rheological properties ( Rheometric Scientific (Waltham, MA) advanced research-grade rheometer with a parallel-plate geometry); Characterization ( Fourier transform infrared (FTIR) spectroscopy; Thermogravimetric analysis (TGA) measurements - Netzsch STA 409PC thermogravimetric analyzer (Selb, Bavaria, Germany); Morphologies of the fracture surfaces (fieldemission scanning electron microscopy (FESEM; S-2150, Hitachi)); Dynamic thermomechanical properties of the nanocomposites (Rheometric Scientific analyzer (DMA 242C, Netzsch)); Tensile properties of the nanocomposites (AG2000 universal material testing machine (Shanghai Hua Long Test Instrument Factory, Shanghai, China); Melting behaviors of the PLA nanocomposites (204 F1 differential scanning calorimeter from Netzsch Gerateban GmbH Instruments).

Processing: Starch blends were prepared by mixing the starch powders with the plasticizing agent (modified commercial drill); Fibers were added; A thermoregulated compression molding press was used to prepare the specimens; A malefemale mold was used to prepare the specimens for mechanical characterization. Mechanical Properties: Tensile tests (Type W Monsanto tensile testing machine); Impact tests (Hounsfield impact testing machine); Morphological Characterization: typical processing defects (trinocular stereomicroscope); voids content of the biocomposites (IA software ImageJ) The voids content of the biocomposites was assessed using image analysis (IA); tensile and impact fracture surfaces (high vacuum Phillips scanning electron microscope). Material preparation: PLA/clay nanocomposites (PLACNs) were prepared by direct melt compounding DK2 with PLA in a HAAKE Polylab rheometer (Thermo Electron Co., USA); Microstructure characterization: X-ray diffractometer (D8 ADVANCE diffractometer (BRUKER AXS Co., Germany); transmission electron micrographs (Tecnai 12 transmission electron microscope (TEM) (PHILIPS Co., Netherlands)); Rheological measurements: rheometer(HAAKE RS600 rheometer, Thermo Electron Co., USA); 200 FRTN1 transducer; TGA analyses: Netzsch Instruments STA409PC. Characterization: structure (FTIR spectroscopy); X-ray q/2q diffraction scans (3 kW Rigaku III diffractometer equipped with Ni-filtered CuKa radiation in the reflection mode); degree of crystallinity (calculated from the integrated area of X-ray diffraction data); Thermal analysis (Perkin Elmer PYRIS Diamond differential scanning calorimeter); Thermal stability (Perkin Elmer TGA 7 Series Apparatus): DMA experiments (Perkin Elmer instrument DMA 7e apparatus equipped with a film tension clamp). In vitro degradation: phosphate buffer saline (PBS) solution under PH 7.2.

Material processing: Unprocessed raw material; Injected; Extruded and injected; Injected and annealed; Extruded, injected and annealed; Chemical structure: Melt flow index (apparatus CEAST 6542/002); Gel permeation chromatography (Hitachi chromatograph, Data were digitally collected using Empower Software from Waters (Milford, MA, USA); Nuclear magnetic resonance (Bruker Advance DPX200). FTIR spectroscopy (Infrared spectra (FTIR/FTNIR Nicolet 6700, using an ATR Smart Orbit; X-ray diffraction (Bruker D8 Advance powder diffractometer). Thermal characterization: Differential scanning calorimetry (Perkin Elmer calorimeter, model Pyris 1 (with 2P intracooler)). Thermogravimetric analysis (Mettler Toledo thermogravimetric analyzer, model TGA-SDTA851). Mechanical behaviour: Tensile tests (type 1A injected specimens and a universal testing machine Galdabini Sun 2500, equipped with a 25 kN load cell) Deformations (video extensometer, a Mintron OS-65D CCD video camera in conjunction with Messphysik Windows based software). PLA nanoparticles fabrication: using acetone as a solvent for PLA; Fabrication of LbL assemblies of PLA nanoparticles; Growth of gold nanoparticles within PLA nanoparticle films; Film biodegradation; Characterization: Molecular weights (gel permeation chromatography on a Waters-2414 instrument with the refractive index detector; z-potential measurements of PLA nanoparticle dispersions (DT 300 equipment (Dispersion Technology)); Transmission electron microscopy (TEM) (JEOL 1200EX electron microscope operated at 100 kV).

Nanocomposite Preparation: dry-mixed; extruder (PCM-30, Ikegai machinery Co.) operated; dried under vacuum. WAXD analyses (MXlabo X-ray diffractometer (MAC Science Co., generator of 3 kW, graphite monochromator, CuKa radiation (wavelength, l 0.154 nm), operated at 40 kV/20 mA). TEM (high-resolution TEM (H-7100; Hitachi Co.). Gel Permeation Chromatography (LC-VP, Shimadzu Co.). Differential Scanning Calorimetry (MDSC, TA2920, TA instruments). Light Scattering and Polar Optical Micrographic Observations (Hv scattering mode with the radiation of a polarized He-Ne laser at 632.8-nm wavelength); optical micrograph (Nikon OPTIPHOTO2-POL); thermostatted hot stage (Linkam RTVMS; Linkam Scientific Instruments, Ltd.). Dynamic Mechanical Analysis: Reometrics Dynamic Analyzer. Flexural Properties and Heat Distortion Temperature: injection machine (IS-80G; Toshiba Machinery Co.); strength (ASTM D-790 method (model 2020; Intesco Co.) The heat distortion temperature (HDT Tester;Toyoseiki Co.) Measurement of O2 Gas Transmission Rates: ASTM D-1434 differential pressure method (GTR-30XAU; Yanaco Co.).

Abstract

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted e

Preparation of PLA based nanocomposites was carried out by using two different nanofillers: expanded graphite and organically modified montmorillonite. The addition and co-addition of these nanofillers to PLA using the melt-blending technique provides nanocomposites that showed significant enhancements in rigidity, thermal stability and fire retardancy of the polymer matrix. The presence of dispersed graphite nanolayers in PLA significantly accelerated the polyester crystallization, whereas the essential increase of thermal resistance is mainly connected to the addition of organoclay. The structure of the nanocomposites was examined by Wide Angle X-ray Scattering Analysis and Transmission Electron Microscopy. The improvement of thermal and mechanical properties obtained by the presence of both nanoparticles in PLA were associated to the good (co)dispersion and to the co-reinforcement effect, whilst the fire retardant properties were found to be related to the combined additive action of both nanofillers. (C) 2010 Elsevier Ltd. All rights reserved. In the given research paper, the effects of reinforcing polylactid (PLA) and poly(3-hydroxybutyrate-co-3hydroxyvalerate) (PHBV) biopolymers on the mechanical performance were studied. Both PLA and PHBV were compounded with man-made cellulose, jute and abaca fibres. The test bar specimens were processed via injection moulding. Various testing methods, including tensile and impact tests, were used to investigate the composites' mechanical performance. Scanning electron microscopy was carried out to study the fibre-matrix interphasial adhesion. To determine the fibre-size distribution, optical microscopy was used. Finally, the obtained results were compared to composites on PP basis with the same reinforcing fibres. The reinforcing with fibres increased the tensile stiffness and strength significantly: however, depending on the fibre type, different improvements of the mechanical parameters were achieved. The main enhancement was realised in impact and tensile strength by reinforcing biopolymers with man-made cellulose fibres. SEM photographs show a largely differing fibre/matrix bonding for PLA and PHBV compared to PP composites. The broadest fibre-size distribution can be found in abaca composites. (c) 2010 Elsevier Ltd. All rights reserved. Polylacticle-based systems composed of an organoclay (Cloisite (R) 30B) and/or a compatibilizer (Exxelor VA 1803) prepared by melt blending were investigated. Two types of not compatibilized nanocomposites containing 3 wt% or 10 wt% of the organoclay were studied to reveal the effect of the filler concentration on the nanostructure and physical properties of such systems. The 3 wt%nanocomposite was also additionally compatibilized in order to improve the nanoclay dispersion. Neat polylactide and polylactide with the compatibilizer processed in similar conditions were used as reference samples. The X-ray investigations showed the presence of exfoliated nanostructure in 3 wt%nanocomposite. Compatibilization of such system noticeably enhanced the degree of exfoliation of the organoclay. Viscoelastic spectra (DMTA) showed an increase of the storage and loss moduli with the increase of the organoclay content and dispersion. Dielectric properties of the nanocomposites show a weak influence of the nanoclay on segmental (alpha(s)) and local (beta)-relaxations in PLA, except for the highest nanoclay content. Above T-g a strong increase of dc conductivity related to ionic species in the clay is observed. It gives rise also to the Maxwell-Wagner-Sillars interfacial polarization and both real and imaginary parts of strongly increase. In the temperature dependence of low frequency dielectric constant and mechanical moduli (at 1 Hz) an additional maximum around 80-90 degrees C is observed due to cold crystallization of PLA. (c) 2007 Elsevier Ltd. All rights reserved.

Purpose: Perspective applications of nanocomposites in biomedical applications are investigated in this work by producing intercalated dispersions of clays into a biodegradable polymer matrix. Poly(lactic acid) (PLA) was selected being produced from renewable resources and approved by the Food and Drug Administration for medical use. In order to improve PLA mechanical properties and to accelerate its degradation, different layered silicate nanoclays are added: montmorillonites and fluorohectorites, without or with organic modifiers. Preparation, characterization, mechanical properties and biodegradation in blood plasma are evaluated. Results: New biodegradable materials were obtained, with improved mechanical properties (Young modulus, Peak stress and Strain at break) and with increased degradation rate (weight loss and lactic acid release). (C) 2009 Elsevier Ltd. All rights reserved.

Biopolymer nanocomposites, which have attracted much attention due to their biodegradability and biocompatibility, have been prepared by melt blending polylactic acid (PLA)/polycaprolactone (PCL) and two types of organoclay (OMMT) include octadecylamine-montmorillonite (ODA-MMT) and fatty hydroxamic acid- montmorillonite (FHA-MMT). Materials were characterized using X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), elemental analysis and scanning electron microscopy (SEM). Mechanical properties were also investigated for these nanocomposites. The nanocomposites showed increasing mechanical properties and thermal stability. XRD results indicated that the materials formed intercalated nanocomposites. SEM morphology showed that increasing content of OMMT reduces the domain size of phase separated particles. Additionally, a solution casting process has been used to prepare these nanocomposites and characterized to compare these results with above process. These nanocomposites offer potential for diversification and application of biopolymer due to their good properties such as improved thermal and mechanical properties.

Poly(lactic acid) (PLA)/SiO2 nanocomposites were prepared via melt mixing with a Haake mixing method. To improve the dispersion of nanoparticles and endow compatibility between the polymer matrix and nanosilica, SiO2 was surface-modified with oleic acid (OA). The interfacial adhesion of the PLA nanocomposites was characterized by field-emission scanning electron microscopy. The storage modulus and glass-transition temperature values of the prepared nanocomposites were measured by dynamic mechanical thermal analysis. The linear and nonlinear dynamic rheological properties of the PLA nanocomposites were measured with a parallel-plate rheometer. The effects of the filling content on the dispersability of the OA-SiO2 nanoparticles in the PLA matrix, the interface adhesion, the thermomechanical properties, the rheological properties, and the mechanical properties were investigated. Moreover, the proper representation of the oscillatory viscometry results provided an alternative sensitive method to detect whether aggregation formed in the polymeric nanocomposites. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2866-2873, 2010

Natural fiber reinforced starch polymers are processed by compression molding. Potato, sweet potato, and corn starch are used as matrices. Three types of natural fibers, namely sisal, jute, and cabuya, are used in concentrations varying from 2.5 to 12.5% w/w in the composites. Different plasticizers are used for the starch polymers, such as water and glycerol. Mechanical properties are assessed by tensile and impact tests. In both cases, improved mechanical properties are obtained at increasing fiber contents. Tensile strength appears to be markedly improved with the addition of 10% by weight of sisal fibers, while the best results for impact strength are obtained for cabuya fibers.

Polylactide/clay nanocomposites (PLACNs) were prepared by melt intercalation. The intercalated structure of PLACNs was investigated using XRD and TEM. Both the linear and nonlinear rheological properties of PLACNs were measured by parallel plate rheometer. The results reveal that percolation threshold of the PLACNs is about 4 wt%, and the network structure is very sensitive to both the quiescent and the large amplitude oscillatory shear(LAOS) deformation. The stress overshoots in the reverse flow experiments were strongly dependent on the rest time and shear rate but shows a strainscaling response to the startup of steady shear flow, indicating that the formation of the long-range structure in PLACNs may be the major driving force for the reorganization of the clay network. The thermal behavior of PLACNs was also characterized. However, the results show that with the addition of clay, the thermal stability of PLACNs decreases in contrast to that of pure PLA. (c) 2006 Elsevier Ltd. All rights reserved.

In this study, the biodegradable poly(lactic acid) (PLA)/montmorillonite (MMT) nanocomposites were successfully prepared by the solution mixing process of PLA polymer with organically-modified montmorillonite (m-MMT), which was first treated by n-hexadecyl trimethylammonium bromide (CTAB) cations and then modified by biocompatible/biodegradable chitosan to improve the chemical similarity between the PLA and m-MMT. Both X-ray diffraction data and transmission electron microscopy images of PLA/m-MMT nanocomposites indicate that most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties and thermal stability of the PLA/m-MMT nanocomposites performed by dynamic mechanical analysis and thermogravimetric analysis have significant improvements in the storage modulus and 50% loss in temperature when compared to that of neat PLA matrix. The degradation rates of PLA/m-MMT nanocomposites are also discussed in this study. (c) 2006 Elsevier Ltd. All rights reserved.

The processing of poly(lactic acid) (injection and extrusion/injection) as well as annealing of processed materials were studied in order to analyze the variation of its chemical structure, thermal degradation and mechanical properties. Processing of PLA was responsible for a decrease in molecular weight, as determined by GPC, due to chain scission. The degree of crystallinity was evaluated by means of differential scanning calorimetry and X-ray diffraction. It was found that mechanical processing led to the quasi disappearance of crystal structure whereas it was recovered after annealing. These findings were qualitatively corroborated by means of FTIR. By analyzing H-1 NMR and C-13 NMR chemical shifts and peak areas, it was possible to affirm that the chemical composition of PLA did not change after processing, but the proportion of methyl groups increased, thus indicating the presence of a different molecular environment. The thermal stability of the various materials was established by calculating various characteristic temperatures from thermograms as well as conversion and conversion derivative curves. Finally, the mechanical behaviour was determined by means of tensile testing (Young modulus, yield strength and elongation at break). (C) 2009 Elsevier Ltd. All rights reserved.

We designed and fabricated multilayer assemblies of biodegradable poly(lactic acid) (PLA) nanoparticles based on hydrogen-bonding or electrostatic interactions. The PLA nanoparticles were prepared by precipitation method and their surface charge was switched by modified precipitation in the presence of poly(ethylene imine) (PEI). Moreover, gold nanoparticles were grown within the PLA nanoparticle assemblies either through UV-irradiation or under mild reducing conditions to create biodegradable nanocomposites with distinct optical response which allows monitoring biodegradation of the films. The nanocomposite coatings of PLA nanoparticles were enzymatically degraded by alpha-chymotrypsin. We demonstrated that the biodegradation process can be colorimetrically monitored with UV-vis spectroscopy thus opening the way for facile and real-time monitoring useful for biotechnology applications. (C) 2010 Elsevier Ltd. All rights reserved.

Our continuing research on the preparation, characterization, materials properties, and biodegradability of polylactide (PLA)/organically modified layered silicate (OMLS) nanocomposites has yielded results on PLA/montmorillonite nanocomposites. Montmorillonite (mmt) modified with dimethyldioctadecylammonium cation was used as an OMLS for nanocomposite preparation. The internal structure of nanocomposites on the nanometer scale was established with the use of wide-angle X-ray diffraction patterns and transmission electron micrographic observation. All nanocomposites exhibited significant improvement in crystallization behavior, mechanical properties, flexural properties, heat distortion temperature, and O2 gas permeability when compared with pure PLA.

rcalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility a

PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed b

were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studi

MgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differe

omposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (Tm),

try analyzer (TG). The melting temperature (Tm), glass transition temperature (Tg), crystallization temperature (Tc), degree of crystallinity (Xc), and therm

erature (Tc), degree of crystallinity (Xc), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properti

been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.