Effect of maleated polypropylene and impact modifiers on the morphology and mechanical properties of PP/Mica composites

Composites of polypropylene (PP) with mica powder and impact modifiers were produced by internal mixer. A major drawback in the use of mica‐filled PP is its low impact resistance. In the present study, the effect of the maleated PP (MAPP) and impact modifiers was evaluated on the composite properties separately and together. Thus, two different styrene‐ethylene/butylene‐styrene triblock copolymers (SEBS) and one ethylene‐propylene‐diene terpolymer (EPDM) have been used as impact modifiers in the PP‐mica composites. Addition of MAPP had a negative effect on the composite notched impact strength and elongation at break but had a positive effect on tensile strength when used together with impact modifiers. All three elastomers increased the impact strength of the PP‐mica composites but the addition of maleated SEBS (SEBS‐MA) granted the greatest improvement in impact strength. It was inferred from the scanning electron microscopy that SEBS‐MA had a stronger interaction with mica surface than the other impact modifiers. POLYM. COMPOS., 27:614–620, 2006. © 2006 Society of Plastics Engineers     

Influence of thermoplastic elastomers on adhesion in polyethylene–wood flour composites

The mechanical properties of recycled low-density polyethylene/wood flour (LDPE/WF) composites are improved when a maleated triblock copolymer styrene–ethylene/butylene–styrene (SEBS–MA) is added as a compatibilizer. The composites' tensile strength reached a maximum level with 4 wt % SEBS–MA content. The compatibilizer had a positive effect on the impact strength and elongation at break but decreased the composites' stiffness. Dynamic mechanical thermal analysis (DMTA), a lap shear adhesion test, and a scanning electron microscope (SEM) were used to investigate the nature of the interfacial adhesion between the WF/SEBS and between the WF/SEBS–MA. Tan δ peak temperatures for the various combinations showed interaction between the ethylene/butylene (EB) part of the copolymer and the wood flour in the maleated system. The shear lap test showed that adhesion between the wood and SEBS–MA is better than between the wood and SEBS. The electron microscopy study of the fracture surfaces confirmed good adhesion between the wood particles and the LDPE/SEBS–MA matrix. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1845–1855, 1998     

Impact modification of polypropylene‐based composites using surface‐coated waste rubber crumbs

Blends of maleated polypropylene (MAPP) with high contents of waste rubber powder, namely ground tire rubber and waste ethylene propylene diene monomer (EPDM) powder, were used as impact modifiers for polypropylene (PP) based composites with different reinforcements (hemp, talc, and milled glass fiber). Adding reinforcements led to increase in modulus (tensile, flexural, and torsion moduli) of PP, while its impact strength decreased noticeably. Impact modification of PP‐based composites was successfully performed via inclusion of MAPP/waste rubber compounds, especially compounds containing waste EPDM powder. Inclusion of such impact modifiers increased impact strength of composites over 80%. The effects of impact modification were more significant for hemp‐ and glass‐filled composites compared to composites containing talc. However, slight decrease in tensile, flexural, and torsion moduli (up to 30%) of the composites was also observed after inclusion of impact modifiers. POLYM. COMPOS., 35:2280–2289, 2014. © 2014 Society of Plastics Engineers     

Preparation and performance characteristics of short‐glass‐fiber/maleated styrene–ethylene–butylene–styrene/polypropylene hybrid composites

Eighty/twenty polypropylene (PP)/styrene–ethylene–butylene–styrene (SEBS) and 80/20 PP/maleated styrene–ethylene–butylene–styrene (SEBS‐g‐MA) blends reinforced with 30 wt % short glass fibers (SGFs) were prepared by extrusion and subsequent injection molding. The influence of the maleic anhydride (MA) functional group grafted to SEBS on the properties of SGF/SEBS/PP hybrid composites was studied. Tensile and impact tests showed that the SEBS‐g‐MA copolymer improved the yield strength and impact toughness of the hybrid composites. Extensive plastic deformation occurred at the matrix interface layer next to the fibers of the SGF/SEBS‐g‐MA/PP composites during impact testing. This was attributed to the MA functional group, which enhanced the adhesion between SEBS and SGF. Differential scanning calorimetry measurements indicated that SEBS promoted the crystallization of PP spherulites by acting as active nucleation sites. However, the MA functional group grafted to SEBS retarded the crystallization of PP. Finally, polarized optical microscopy observations confirmed the absence of transcrystallinity at the glass‐fiber surfaces of both SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrid composites. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1303–1311, 2002     

Drop weight impact and work of fracture of short glass fiber reinforced polypropylene composites toughened with elastomer

Short glass fiber (SGF) reinforced polypropylene composites toughened with styrene‐ethylene butylene‐styrene (SEBS) or maleated SEBS (SEBS‐g‐MA) triblock copolymer were injection molded. Charpy drop‐weight impact properties and the impact essential work of fracture (EWF) of the SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrids were investigated. Drop‐weight impact results revealed that the SGF/SEBS/PP hybrid exhibits higher impact strength than the SGF/SEBS‐g‐MA/PP hybrid at low impact speeds. This was derived from the pull‐out of fibers from the SGF/SEBS/PP hybrid. At high impact speeds, the impact strength of the SGF/SEBS‐g‐MA/PP hybrid was slightly higher than that of the SGF/SEBS/PP hybrid. Impact EWF measurements showed that the hybrids only exhibit specific essential work (W_e) at a high impact speed of 3 ms⁻¹. The non‐essential work does not occur in the hybrids under high impact rate loading conditions. Moreover, SEBS or SEBS‐g‐MA addition was beneficial in enhancing the high‐rate specific essential work of the SGF/SEBS/PP and SGF/SEBS‐g‐MA/PP hybrid composites.     

软木纤维增强PP复合材料的研究

采用软木纤维作为增强材料提高聚丙烯性能。为了改善软木纤维和聚丙烯母体之间的相容性,用马来酸酐接枝聚丙烯(MAPP)对软木纤维进行接枝处理,用MAPP或用三元乙丙橡胶(EPDM)对软木纤维进行改性处理。结果表明,与未经处理木纤维的复合材料相比,三种处理方法都使复合材料的热性能、加工性能和力学性能有了较大的提高。用MAPP接枝和用MAPP表面处理木纤维的方法比用EPDM表面处理木纤维的方法在提高复合材料热性能、加工流动性和拉伸强度方面更为显著。用EPDM表面处理木纤维在改善复合材料的冲击强度、断裂伸长率上更明显。此外,木纤维在复合材料中的浓度对复合材料其它性能的影响,以及MAPP接枝木纤维和MAPP处理木纤维的不同实验结果也进行了评价。     

Conifer fibers as reinforcing materials for polypropylene‐based composites

Conifer fibers were used to reinforce polypropylene (PP). To improve the compatibility between the conifer fibers and the PP matrix, the fibers were either grafted with maleated PP (MAPP), treated by adding MAPP, or mixed with ethylene/propylene/diene terpolymer (EPDM). The treatments resulted in improved processing, as well as improvements in the thermal and mechanical properties of the resultant composites compared with the composites filled with untreated conifer fibers. Moreover, MAPP grafting and MAPP treating displayed more obvious benefits than EPDM treating in terms of thermal properties, processing flowability, and tensile strength improvements. EPDM treating also produced more significant benefits than either MAPP grafting or MAPP treating in terms of impact strength and tensile elongation improvements. These improvements were attributed to surface coating of the fibers when EPDM was used. In addition, the effect of the concentration of the conifer fibers on the properties of the composites and the difference between MAPP grafting and MAPP treating were evaluated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2833–2841, 2001     

Effect of fiber pretreatment condition on the interfacial strength and mechanical properties of wood fiber/PP composites

The effect of fiber surface pretreatment on the interfacial strength and mechanical properties of wood fiber/polypropylene (WF/PP) composites are investigated. The results demonstrate that fiber surface conditions significantly influence the fiber–matrix interfacial bond, which, in turn, determines the mechanical properties of the composites. The WF/PP composite containing fibers pretreated with an acid–silane aqueous solution exhibits the highest tensile properties among the materials studied. This observation is a direct result of the strong interfacial bond caused by the acid/water condition used in the fiber pretreatment. Evidence from coupling chemistry, rheological and electron microscopic studies support the above conclusion. When SEBS‐g‐MA copolymer is used, a synergistic toughening effect between the wood fiber and the copolymer is observed. The V‐notch Charpy impact strength of the WF/PP/SEBS‐g‐MA composite is substantially higher than that of the WF/PP composite. The synergistic toughening mechanisms are discussed with respect to the interfacial bond strength, fiber‐matrix debonding, and matrix plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1000–1010, 2000     

Effects of styrene–ethylene–butylene–styrene based additives on the mechanical properties of rice hull/polypropylene composites

The purpose of this study was to improve the mechanical properties (such as tensile, flexural, and impact strength) of rice hull/polypropylene composites, with the use of styrene–ethylene–butylene–styrene copolymer (SEBS) and maleated styrene–ethylene–butylene–styrene copolymer (SEBS-MA). The results suggested that both types of additives increased the impact strength of the composites significantly as their contents increased. However, only SEBS-MA improved the tensile and flexural strength of the composites. The results also indicated that the composites with SEBS-MA consistently showed better mechanical properties than the SEBS counterparts for all the contents. POLYM. ENG. SCI., 47:1148–1155, 2007. © 2007 Society of Plastics Engineers     

Influence of phase modifiers on morphology and properties of thermoplastic elastomers prepared from ethylene propylene diene rubber and isotactic polypropylene

A series of thermoplastic elastomers (TPEs) were prepared from a binary blend of ethylene propylene diene rubber (EPDM) and isotactic polypropylene (iPP) using different types of phase modifiers. The influence of sulphonated EPDM, maleated EPDM, styrene‐ethylene‐co‐butylene‐styrene block copolymer, maleated PP, and acrylated PP as phase modifiers showed improved physico‐mechanical properties (like maximum stress, elongation at break, moduli, and tension set). Scanning electron and atomic force microscopy studies revealed better morphologies obtained with these phase modified EPDM‐iPP blends. The dependence of the phase modifier type and concentration was optimized with respect to the improvement in physical properties and morphology of the blends. Physical properties, dynamic mechanical properties, and morphology of these blends were explained with the help of interaction parameter, melt viscosity, and crystallinity of the blends. Theoretical modeling showed that Kerner, Ishai‐Cohen, and Paul models predicted the right morphology–property correlation for the prepared TPEs. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Preparation and properties of styrene–ethylene–butylene–styrene block copolymer/clay nanocomposites: I. Effect of clay content and compatibilizer types

BACKGROUND: Polymer/clay (silicate) systems exhibit great promise for industrial applications due to their ability to display synergistically advanced properties with relatively small amounts of clay loads. The effects of various compatibilizers on styrene–ethylene–butylene–styrene block copolymer (SEBS)/clay nanocomposites with various amounts of clay using a melt mixing process are investigated. RESULTS: SEBS/clay nanocomposites were prepared via melt mixing. Two types of maleated compatibilizers, styrene–ethylene–butylene–styrene block copolymer grafted maleic anhydride (SEBS‐g‐MA) and polypropylene grafted maleic anhydride (PP‐g‐MA), were incorporated to improve the dispersion of various amounts of commercial organoclay (denoted as 20A). Experimental samples were analyzed using X‐ray diffraction and transmission electron microscopy. Thermal stability was enhanced through the addition of clay with or without compatibilizers. The dynamic mechanical properties and rheological properties indicated enhanced interaction for the compatibilized nanocomposites. In particular, the PP‐g‐MA compatibilized system conferred higher tensile strength or Young's modulus than the SEBS‐g‐MA compatibilized system, although SEBS‐g‐MA seemed to further expand the interlayer spacing of the clay compared with PP‐g‐MA. CONCLUSION: These unusual results suggest that the matrix properties and compatibilizer types are crucial factors in attaining the best mechanical property performance at a specific clay content. Copyright © 2007 Society of Chemical Industry     

Modified polypropylene wood flour composites. II. Fracture,deformation, and mechanical properties

The effect of grafting level of maleic anhydride (MA) in the maleated polypropylene (PPMA) on the fracture, deformation mechanisms, and mechanical properties of polypropylene (PP) wood flour composites was studied. Tensile strength, elongation at break, and impact strength are noticeably improved with addition of interfacial modifiers as maximum values of the examined mechanical properties were detected when concentration of MA in the compatibilizer was 1 wt %. To explore the microstructure and deformation mechanisms, scanning electron microscopy was employed. It was found that low concentrations of MA up to 1 wt % led to the creation of a thin and irregular polymer layer assisted formation of fibrillated plastic deformation zone around the wood particles, while the bulk PP matrix experienced voiding and brittle fracture. Higher concentrations of MA fetch to stronger interaction between PP and wood flour, the reason for brittle fracture and reduced ductility of the matrix. The impact fracture behavior of the composites during Instrumented impact tests is also discussed with respect to the interfacial bond strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1286–1292, 2004     

Mechanical properties of wollastonite‐reinforced polypropylene composites modified with SEBS and SEBS‐g‐MA elastomers

Mechanical properties of isotactic polypropylene/wollastonite/styrene rubber block copolymers (iPP/wollastonite/SRBC) composites were studied as a function of elastomeric poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) triblock copolymer (SEBS) and SEBS grafted with maleic anhydride (SEBS‐g‐MA) content from 0 to 20 vol%. Microphase morphology was stronger influenced by SRBC elastomers than by different wollastonite types. Higher encapsulation ability of SEBS‐g‐MA than SEBS caused more expressive core‐shell morphology and consequently higher notched impact strength as well as yield parameters, but lower Young's modulus. Higher ductility of the composites with SEBS than with SEBS‐g‐MA has been primarily caused by better miscibility of the polypropylene chains with SEBS molecules. Surface properties of components and adhesion parameters also indicated that adhesion at SEBS‐g‐MA/wollastonite interface, which was stronger than the one at the SEBS/wollastonite interface, influenced higher encapsulation of wollastonite particles by SEBS‐g‐MA. POLYM. ENG. SCI., 47:1873–1880, 2007. © 2007 Society of Plastics Engineers     

Process–structure–property relationship in ternary short‐glass‐fiber/elastomer/polypropylene composites

Short‐glass‐fiber (SGF)‐reinforced polypropylene (PP) composites toughened with a styrene/ethylene butylene/styrene (SEBS) triblock copolymer were injection molded after extrusion. Furthermore, a maleic anhydride (MA)‐grafted SEBS copolymer (SEBS‐g‐MA) was used as an impact modifier and compatibilizer. The effects of the processing conditions and compatibilizer on the microstructure and tensile and impact performance of the hybrid composites were investigated. In the route 1 fabrication process, SGF, PP, and SEBS were blended in an extruder twice, and this was followed by injection molding. In route 2, or the sequential blending process, the elastomer and PP were mixed thoroughly before the addition of SGF. In other words, either PP and SEBS or PP and SEBS‐g‐MA pellets were premixed in an extruder. The produced pellets were then blended with SGF in the extruder, and this was followed by injection molding. The SGF/SEBS‐g‐MA/PP hybrid fabricated by the route 2 process exhibited the highest modulus, yield stress, tensile stress at break, Izod impact energy, and Charpy drop weight impact strength among the composites investigated. This was due to the formation of a homogeneous SEBS elastomeric interlayer at the SGF and matrix interface of the SGF/SEBS‐g‐MA/PP hybrid. This SEBS rubbery layer enhanced the interfacial bonding between SGF and the matrix of the SGF/SEBS‐g‐MA/PP hybrid. The correlations between the processing, microstructure, and properties of the hybrids were investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1384–1392, 2003     

Rheological behaviors of glass bead‐ and wollastonite‐filled polypropylene composites modified with thermoplastic elastomers

Steady‐ and oscillatory‐shear rheological behaviors of polypropylene/glass bead (PP/GB) and PP/wollastonite (PP/W) melts modified with thermoplastic elastomers, poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) copolymer (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS‐g‐MA), were examined by means of a parallel‐plate rheometer. With adding the elastomers (SEBS and SEBS‐g‐MA) and fillers (spherical GB and acicular W) to PP, viscosity especially at low shear rates and shear‐thinning flow behavior at high shear rates were pronounced as evidenced quantitatively by Carreau–Yasuda (CY) parameters, but Cox–Merz analogy became weakened. Besides, melt‐elasticity in terminal region and relaxation time (t_c) in crossing point increased, indicating an enhancement in quasi‐solid behavior of molten PP. Comparing with the elastomers, rheological behaviors of molten PP were more influenced with adding the rigid fillers, especially with W due to distinct acicular shape of W particles. SEBS‐g‐MA elastomer more affected rheological behaviors of the ternary composites than SEBS elastomer, implying that SEBS elastomer and the filler particles behaved individually (i.e., development of separate microstructure) in (PP/GB)/SEBS and (PP/W)/SEBS ternary composites, but core‐shell microstructure developed with strong interfacial adhesion by adding SEBS‐g‐MA elastomer, and the filler particles encapsulated with the thick SEBS‐g‐MA elastomer interlayer (i.e., core‐shell particles) acted like neither big elastomer particles nor like individual rigid particles in melt‐state. Moreover, effects of SEBS‐g‐MA elastomer reached a maximum on rheological behaviors of (PP/W)/SEBS‐g‐MA ternary composite, indicating a synergy between core‐shell microstructure and acicular W particles. Correlations between oscillatory‐shear flow properties and microstructures of the blends and composites were evaluated using Cole–Cole (CC), Han–Chuang (HC), and van Gurp–Palmen (vGP) plots. COMPOS., 2012. © 2012 Society of Plastics     

Mechanical properties and nonisothermal crystallization of polyamide 6/carbon fiber composites toughened by maleated elastomers

Polyamide 6/carbon fiber (PA6/CF) composites toughened with maleated elastomers were prepared by melt blending using twin‐screw extruder followed by injection molding. Three kinds of maleated elastomers, maleic anhydride (MAH)‐grafted ethylene‐vinyl acetate copolymer (EVA‐g‐MAH), MAH‐grafted ethylene‐propylene‐diene terpolymer (EPDM‐g‐MAH), and MAH‐grafted hydrogenated styrene‐butadiene‐styrene (SEBS‐g‐MAH), were used to toughen the PA6/CF composites. The mechanical properties, morphology, nonisothermal crystallization, and subsequent melting behavior of PA6 hybrid composites were investigated. Mechanical tests indicated that incorporation of elastomers improved the impact properties of CF‐reinforced PA composites accompanied with loss of tensile strength and modulus. It was observed from scanning electron microscope photographs that modification with maleated elastomers improved the interfacial adhesion between the CFs and PA6 matrix. Nonisothermal crystallization behavior showed that three kinds of elastomers had negative effect on crystallization and retarded crystallization of PA6. Kissinger's analysis illustrated that addition of CF slightly increased the crystallization activation energy of PA6, whereas incorporation of elastomers reversed it compared with pure PA6. Furthermore, a slight decrease in crystallinity and melting peak of the composites after incorporation of elastomers was observed compared with pure PA6. Polarizing optical microscope results showed that the transcrystallinity phenomenon seemed to be also affected when the matrix was added by the elastomers. POLYM. COMPOS., 35:2170–2179, 2014. © 2014 Society of Plastics Engineers     

SBS and SEBS block copolymers as impact modifiers for polypropylene compounds

Blends of polypropylene (PP) and thermoplastic elastomers (TPE), namely SBS (styrene‐butadiene‐styrene) and SEBS (styrene‐ethylene/1‐butene‐styrene) block copolymers, were prepared to evaluate the effectiveness of the TPE type as an impact modifier for PP and influence of the concentration of elastomer on the polymer properties. Polypropylene homopolymer (PP‐H) and ethylene–propylene random copolymer (PP‐R) were evaluated as the PP matrix. Results showed that TPEs had a nucleating effect that caused the PP crystallization temperature to increase, with SBS being more effective than SEBS. Microstructure characterization tests showed that in most cases PP/SEBS blends showed the smallest rubber droplets regardless of the matrix used. It was seen that SEBS is a more effective toughening agent for PP than SBS. At 0°C the Izod impact strength of the PP‐H/SEBS 30% b/w blend was twofold higher than the SBS strength, with the PP‐R/SEBS 30% b/w blend showing no break. A similar behavior on tensile properties and flexural modulus were observed in both PP/TPE blends. Yield stress and tensile strength decreased and elongation at break increased by expanding the dispersed elastomeric phase in the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 254–263, 2005     

Effects of carbon nanofibers on the fracture,mechanical, and thermal properties of PP/SEBS‐g‐MA blends

Polypropylene/maleated (styrene‐ethylene‐butadiene‐styrene) (PP/SEBS‐g‐MA) blends reinforced with 0.2–2.5 wt% carbon nanofibers (CNFs) were prepared by injection molding. The structure, thermal, mechanical, and fracture behaviors of PP/SEBS‐g‐MA blends and their nanocomposites were studied. Wide‐angle X‐ray diffraction (WAXD) results showed that the SEBS‐g‐MA and/or CNF additions do not induce a structural change of PP. Tensile measurements showed that the Young's modulus and tensile yield strength increase with the increasing filler content. Izod impact and essential work of fracture test results demonstrated that CNFs are beneficial to improve the impact strength and specific essential work of fracture of PP/SEBS‐g‐MA blends. Therefore, tough PP‐nanocomposites can be achieved by melt‐blending low fractions of CNFs and appropriate elastomer contents. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Phase modification of SEBS block copolymer by different additives and its effect on morphology,mechanical and dynamic mechanical properties

The objective of this study is to examine the phase modification of styrene–ethylene butylene–styrene (SEBS) block copolymer by different additives and its influence on morphology and mechanical, and dynamic mechanical properties. The additives chosen are the coumarone–indene (CI), phenol–formaldehyde (PF), paraffin hydrocarbon (PAHY) resins, as well as aromatic oil (AO), polystyrene (PS), polypropylene (PP), ethylene vinyl acetate (EVA) (VA 28 and 45%), and ethylene propylene diene monomer (EPDM) rubber. It is interesting to note that of all the additives, PP has the most prominent effect. The mechanical properties of SEBS polymer are enhanced to a large extent by PP. The value of tan δ maximum of SEBS at both the low and the high temperature transitions is decreased. All the resins and PS increase the storage modulus and the tensile modulus of the SEBS polymer. CI resin and AO modify the hard and soft phases of SEBS polymer. AO, EPDM rubber, and EVA lower the mechanical strength of the SEBS polymer. The results are explained on the basis of morphologystudied with the help of scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2015–2025, 1998     

Morphological,mechanical, and physical properties of composites made with wood flour‐reinforced polypropylene/recycled poly(ethylene terephthalate) blends

Wood flour (WF)‐filled composites based on a polypropylene (PP)/recycled polyethylene terephthalate (r‐PET) matrix were prepared using two‐step extrusion. Maleic anhydride grafted polypropylene (MAPP) was added to improve the compatibility between polymer matrices and WF. The effects of filler and MAPP compatibilization on the water absorption, mechanical properties, and morphological features of PP/r‐PET/WF composites were investigated. The addition of MAPP significantly improved mechanical properties such as tensile strength, flexural strength, tensile modulus, and flexural modulus compared with uncompatibilized composites, but decreased elongation at break. Scanning electron microscopic images of fracture surface specimens revealed better interfacial interaction between WF and polymer matrix for MAPP‐compatibilized PP/r‐PET/WF composites. MAPP‐compatibilized PP/r‐PET/WF composites also showed reduced water absorption due to improved interfacial bonding, which limited the amount of absorbable water molecules. These results indicated that MAPP acts as an effective compatibilizer in PP/r‐PET/WF composites. POLYM. COMPOS., 38:1749–1755, 2017. © 2015 Society of Plastics Engineers