Mechanical, Morphological and Thermal Properties of Pine Needle-Reinforced Polymer Composites

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Mechanical, Morphological and Thermal Propertiesof SEBS, SIS and SBR-type Thermoplastic ElastomersToughened High Impact PolystyreneMünir Taşdemir a & Ebru Uluğ ba Department of Metallurgical and Materials Engineering, Technology Faculty, MarmaraUniversity, Goztepe, Istanbul, Turkeyb Institute for Graduate Studies in Pure and Applied Science, Marmara University, Goztepe,Istanbul, Turkey

Available online: 24 Jan 2012

To cite this article: Münir Taşdemir & Ebru Uluğ (2012): Mechanical, Morphological and Thermal Properties of SEBS, SIS andSBR-type Thermoplastic Elastomers Toughened High Impact Polystyrene, Polymer-Plastics Technology and Engineering, 51:2,164-169

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Mechanical, Morphological and Thermal Properties of SEBS,SIS and SBR-type Thermoplastic Elastomers ToughenedHigh Impact Polystyrene

Munir Tasdemir1 and Ebru Ulug21Department of Metallurgical and Materials Engineering, Technology Faculty, Marmara University,Goztepe, Istanbul, Turkey2Institute for Graduate Studies in Pure and Applied Science, Marmara University, Goztepe, Istanbul,Turkey

In this article the effect of PS on the mechanical, thermal andmorphological properties of SEBS, SIS and SBR type elastomers–based material was investigated in flow direction 0o and flow direc-tion 90o. The structure and properties of the composites are charac-terized using a scanning electron microscopy (SEM), Differentialscanning calorimeter (DSC) and Energy dispersive X-ray spec-troscopy (EDS). Furthermore, SEBS/PS, SIS/PS and SBR/PSpolymer blends were subjected to examinations to obtain their elas-ticity modulus, yield strengths, strength at break, elongation atbreak, hardness, Izod impact strength, wear rate, melt flow index(MFI), vicat softening point and heat deflection temperature(HDT). In two directions, with the increased amount of HIPS inSEBS/HIPS/CaCO3, SIS/HIPS/CaCO3 and SBR/HIPS polymerblends, the elasticity modulus, yield strengths, strength at break,hardness, Izod impact strength, MFI, HDT, vicat value and wearrate of the resultant material increased, whereas the elongation atbreak decreased.

Keywords High impact polystyrene; Polymer blends; Styrenebutadiene rubber; Styrene ethylene butadiene styrene;Styrene isoprene styrene; Thermoplastic elastomer

INTRODUCTION

Elastomers, so-called natural and synthetic rubbers, arewidely used in automotive and other industries for theirmany special properties. Elastomers are usually mixed withdifferent materials to increase the values of physicalproperties. Especially, in industrial elastomers, consider-able amount of filler materials is put in blends as a costreducer and physical property riser[1]. Thermoplastic elas-tomers (TPE) belong to a relatively new and small classof engineering plastics.

Nevertheless, they enjoy a steady growth because of theirunusual and very important combination of properties.

During service, TPE behave as elastomers (e.g., as vulca-nized natural rubber) but, in contrast to the classical elasto-mers, they can be processed by means of the conventionaltechniques and equipment utilized for all thermoplastics.This peculiarity of TPE is related to their different type ofcross-linking. Unlike the classical elastomers, TPE arecross-linked by thermally labile aggregates, which meltduring processing and regenerate after cooling down.

This is because TPE are always block copolymerscomprising the so-called ‘‘hard blocks’’ (forming solid crys-tallites or glassy regions), and ‘‘soft blocks’’ (imparting theelastomeric properties)[2]. The thermoplastic elastomersconcern large industrial and commercial fields, as well asacademic and applied research. Often the TPE are con-sidered as being only an important part of the block copo-lymers, but they are present in many other polymericmaterials, as clearly shown by Holden et al.[3,4] andRader[5–7].

They are characterized by a set of properties inherent toblock and graft copolymers, different blends, and somevulcanized materials. Styrene block copolymers are themost widely used TPEs, accounting for close to 45% oftotal TPE consumption worldwide at the close of the twen-tieth century[8]. Styrenic TPEs are usually styrene buta-diene styrene (SBS), styrene ethylene=butylene styrene(SEBS), and styrene isoprene styrene (SIS). Styrenic TPEsusually have about 30 to 40% (wt) bound styrene; certaingrades have a higher bound styrene content.

The polystyrene endblocks create a network of revers-ible physical cross-links which allow thermoplasticity formelt processing or solvation. With cooling or solvent evap-oration, the polystyrene domains reform and harden, andthe rubber network is fixed in position[9]. Principal styrenicTPE markets are: molded shoe soles and other footwear;extruded film=sheet and wire=cable covering; and pressuresensitive adhesives and hot-melt adhesives, viscosity indeximprover additives in lube oils, resin modifiers, and asphalt

Address correspondence to Munir Tasdemir, MarmaraUniversity, Technology Faculty, Department of Metallurgicaland Materials Engineering, Goztepe 34722, Istanbul, Turkey.E-mail: [email protected]

Polymer-Plastics Technology and Engineering, 51: 164–169, 2012

Copyright # Taylor & Francis Group, LLC

ISSN: 0360-2559 print=1525-6111 online

DOI: 10.1080/03602559.2011.618169

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modifiers[4]. A vast amount of research, particularly in thearea of thermoplastic elastomers, has been focused instudying the relation between the processing conditions inextrusion and the final polymer morphology.

Savasci et al. pointed out that the ideal filler materials inelastomers exhibited an increase in bending strength, ulti-mate tensile stress, and toughness and a decrease in cost[10].Matinez et al. reported that mechanical and processingproperties of PS=SBR blend[11]. Sreenivasan et al. investi-gated the mechanical properties and morphology of nitrilerubber toughened polystyrene[12]. Blends of SEBS, SBRand SIS have been studied by many researchers suchas Savadekar et al.[13], Chow et al.[14], Noriman et al.[15],Noriman et al.[16], El-Nashar[17], Botros et al.[18], Tasdemiret al.[19] and Raghu et al.[20].

In this study, the effect of PS on the mechanical, thermaland morphological properties of SEBS, SIS and SBR typeelastomers based shoe sole material was investigated inflow direction 0o and flow direction 90o.

EXPERIMENTAL

Compositions and Materials

Fifteen different polymer composites were prepared.Compositions of SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3

and SBR=HIPS polymer composites that were formed aregiven in Table 1.

Styrene ethylene butylenes styrene block copolymer(SEBS) (calprene H6110) was supplied by Dynasol Elasto-mers (Houston, TX-USA). Total styrene ratio is 30%. Meltflow rate (230�C=2.16 kg) is 1.5 g=10min. Styrene isoprenestyrene block copolymer (SIS) (Europrene Sol T 190) wassupplied Polimeri Europa (Milan, Italy). Its specific gravityis 0.928 g=cm3, melt flow rate (190�C=5.0 kg) is 9.0 g=10min. Styrene ratio is 16%. Styrene butadiene blockcopolymer (SBR) (calprene 411) was supplied by DynasolElastomers (Houston, TX, USA).

Its specific gravity is 0.938 g=cm3, melt flow rate (190�C=5.0 kg) is 1.0 g=10min. Styrene ratio is 30%. High impactpolystyrene (HIPS) (porene PS HI650) was supplied byIRPC public company limited (Bangkok, Thailand). Meltflow rate (200�C=5.0 kg) is 8.0 g=10min. Calcium carbon-ate (CaCO3) (Esen calcite A-3) was supplied by Esenmikronize (Istanbul, Turkey). CaCO3 ratio is �98%. Itsspecific gravity is 2.7 g=cm3, particle size is 2.70–3.30 m.Paraffinic oil was supplied Petroyag (Kocaeli, Turkey).Its density is 0.8576 g=cm3.

Composite Preparation

CaCO3 was dried in a Yamato Vacuum oven ADP-31(Yamato=VWR Scientific Products, Japan) at 110�C for24 h before being blended with SEBS=HIPS and SIS=HIPS.Mechanical premixing of solid compositions was done usinga LB-5601 liquid-solids blender (The Patterson-Kelley Co.,

Inc. east Stroudsburg, PA – USA) brand batch blender at10min.

Samples with various proportions of SEBS=HIPS,SIS=HIPS and SBR=HIPS were produced between150–210�C at 5–14 bar pressure, and a production rateof 40–44 rpm, with a Microsan co-rotating twin-screwextruder (L=D ratio is 30, Ø:25mm, Microsan Instru-ment Inc. Kocaeli-Turkey). Polymer composites werealso dried in Vacuum oven at 110�C for 6 hours afterextrusion. Extrusion conditions are given in Table 2.Plate samples of the granulated polymeric blends weremade in plate machine.

Test Procedure

Composite specimens were conditioned at 23�C and50% humidity for 24 h before testing (ASTM D618).Tensile tests were performed according to ASTM D638specification. They were carried out using a Zwick Z010(Zwick GmbH, Ulm-Germany) testing machine with a loadcell capacity of 10 kN at a cross-head speed of 50mm=min.Hardness test were done according to the ASTM D2240method with Zwick hardness measurement equipment.To investigate fracture behavior, Izod impact test

TABLE 1Composition of the different rubber formulations

GroupsSEBS(%)

HIPS(%)

CaCO3

(%)ParaffinicOil (%)

SEBS=HIPS=CaCO3

1 30 30 10 302 27.5 35 10 27.53 25 40 10 254 22.5 45 10 22.55 20 50 10 20

GroupsSIS(%)

HIPS(%)

CaCO3

(%)ParaffinicOil (%)

SIS=HIPS=CaCO3

1 55 30 10 52 50 35 10 53 45 40 10 54 40 45 10 55 35 50 10 5

Groups SBR (%) HIPS (%)

SBR=HIPS1 65 352 60 403 55 454 50 505 45 55

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(notched) was done at room temperature according to theASTM D256 method with Zwick B5113 impact test device(Zwick GmbH & Co. KG Ulm, Germany).

The wear tests were done according to the DIN 53 516method with Devotrans DA5 (Devotrans quality controltest equipment Istanbul-Turkey) abrasion test equipment.Flow behavior testing of all the mixtures was doneaccording to ISO 1133 standard with Zwick 4100 MFIequipment. The fractured surfaces of the composites were

coated about 10 nm in thickness with gold (Au) (80%)=palladium (Pd) (20%) alloys to prevent electrical chargingby Polaron SC 7620 (Gala Instrumente GmbH, BadSchwalbach-Germany). The surfaces of the prepared sam-ples were observed by the JEOL-JSM 5910 LV (JEOL Ltd.,Tokyo, Japan) scanning electron microscopy (SEM) at anacceleration voltage of 20 kV.

Elemental analysis was done using energy dispersiveX-ray spectroscopy (EDS) (Incax-sight-model: 7274,Oxford Instruments, England). Heat deflection tempera-ture (HDT) and Vicat softening point tests were doneaccording to ISO 75 and ISO 307 standard with determinedby CEAST 6521 (Ceast SpA Pianezza, Italy) HDT-vicattest equipment. Five samples were tested in each set andthe average value was reported.

RESULTS AND DISCUSSION

Mechanical properties of the SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymer composites aregiven in Fig. 1. In two directions (flow direction 0o and flow

TABLE 2Extrusion conditions of the SEBS=HIPS=CaCO3,

SIS=HIPS=CaCO3 and SBR=HIPS polymer composites

ProcessSEBS=HIPS=

CaCO3

SIS=HIPS=CaCO3

SBR=HIPS

Temperature (�C) 150–190 150–190 170–210Pressure (bar) 5–6 5–6 13–14Screw speed (rpm) 40 40 44

FIG. 1. Mechanical properties of the SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymer composites.

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direction 90o) with the increased amount of HIPS in SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymerblends, the elasticity modulus, yield strengths, strength @break, hardness, izod impact strength and wear rate ofthe resultant material increased, whereas the elongation@ break decreased. Because of rigid structure of the HIPS,these values were increased. For example the elasticitymodulus value of the SEBS=HIPS=CaCO3 (Group 1) poly-mer composite was 28.3MPa. However, the increasing ofHIPS contends to the polymer composite resulted in higherelasticity modulus values. Also hardness value of theSEBS=HIPS=CaCO3 (Group 1) polymer composite was77.6 Shore A. However, the increasing of HIPS contendsto the polymer composite resulted in higher harness values.

Similar result was obtained in SIS=HIPS=CaCO3 polymercomposites.

The thermal properties of the polymer composites aregiven in Table 3. As shown in Table 3, the melt flowindex value of the SEBS=HIPS=CaCO3 (Group 1) poly-mer composite was 2.6 g=10min. However, the increasingof HIPS contends to the polymer composite resulted inhigher MFI values. The maximum melt flow indexis observed at Group 5. Similar result was obtained inSIS=HIPS=CaCO3 polymer composites. The melt flowindex value of the SIS=HIPS=CaCO3 (Group 1) polymercomposite was 39.7 g=10min. However, the addition ofHIPS to the polymer composite resulted in higher MFIvalues.

TABLE 3Thermal properties of the SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymer composites

Thermal Properties Group 1 Group 2 Group 3 Group 4 Group 5

SEBS=HIPS=CaCO3

MFI (g=10min) (230�C� 3.8 kg) 2.6� 0 9.2� 2 20.1� 2 24.2� 4 25.2� 2Vicat Softening Point (�C- 1 kg) 57.8 59.8 64.2 67.6 73.2HDT (�C� 1.80MPa) - – – – 52.6

SIS=HIPS=CaCO3

MFI (g=10min) (230�C� 3.8 kg) 39.7� 3 46.9� 5 48.5� 1 50.1� 2 51.1� 1Vicat Softening Point (�C� 1 kg) – – – – –HDT (�C� 1.80MPa) – – – – –

MFI (g=10min) (230�C� 3.8 kg) There was no flow

SBR=HIPSVicat Softening Point (�C� 1 kg) 65.2 66.5 67.8 87.3 91.9HDT (�C� 1.80MPa) 50.3 51.7 52.2 55.3 66.5

FIG. 2. SEM micrographs of the SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymer composites.

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There was no flow in the SBR=HIPS polymer blend. TheHDT and vicat softening temperature measurementsshowed that the addition of HIPS to the SEBS=HIPS=CaCO3 and SBR=HIPS increased the heat deflection tem-perature and vicat softening point values, as shown inTable 3. The HDT and vicat values of SIS=HIPS=CaCO3

polymer composite were not measured. The HDT experi-ment was started at room temperature with a heating rateof 120�C=h and under a load of 1.8MPa

The fracture surfaces of the polymer composites wereexamined via SEM in an attempt to correlate the mechan-ical properties to the microstructural characteristics. Scan-ning electron micrographs of fractured surfaces of theSEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPSpolymer composites taken after Izod impact tests areshown in Figure 2 and energy dispersive X-ray spec-troscopy (EDS) spectrums of the polymer composite aregiven in Figure 3.

The micrographs indicate that the CaCO3 particulatesare homogeneously dispersed on the fractured surfaces ofpolymer matrix. With addition of SEBS, SIS and SBR rub-ber to the HIPS, the adhesion and distribution of thepresent phases were considerably enhanced as well.

For example the SEM images of SEBS=HIPS=CaCO3

composites (groups 1–5) given in Figure 2. In this systemthe SEBS particles exist as irregularly shaped domains inthe HIPS matrix.

CONCLUSIONS

In two directions (flow direction 0o and flow direction90o) with the increased amount of HIPS in SEBS=HIPS=CaCO3, SIS=HIPS=CaCO3 and SBR=HIPS polymerblends, the elasticity modulus, yield strengths, strength @break, hardness, izod impact strength, MFI, HDT, vicatvalue and wear rate of the resultant material increased,

whereas the elongation at break decreased. The micro-graphs indicate that the CaCO3 particulates are homoge-neously dispersed on the fractured surfaces of polymermatrix. With addition of SEBS, SIS and SBR rubber tothe HIPS, the adhesion and distribution of the presentphases were considerably enhanced as well.

ACKNOWLEDGMENTS

This work has been supported by the Scientific ResearchProject Program of Marmara University (Project no:FEN-C- YLP-060510-0144). The authors are grateful toMarmara University for their financial support and theprovision of laboratory facilities.

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