Polypropylene/montmorillonite nanocomposites toughened with SEBS‐g‐MA: Structure–property relationship

Polypropylene (PP)/organo‐montmorillonite (Org‐MMT) nanocomposites toughened with maleated styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) were prepared via melt compounding. The structure, mechanical properties, and dynamic mechanical properties of PP/SEBS‐g‐MA blends and their nanocomposites were investigated by X‐ray diffraction (XRD), polarizing optical microscopy (POM), tensile, and impact tests. XRD traces showed that Org‐MMT promoted the formation of β‐phase PP. The degree of crystallinity of PP/SEBS‐g‐MA blends and their nanocomposites were determined from the wide angle X‐ray diffraction via profile fitting method. POM experiments revealed that Org‐MMT particles served as nucleating sites, resulting in a decrease of the spherulite size. The essential work of fracture approach was used to evaluate the tensile fracture toughness of the nanocomposites toughened with elastomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3112–3126, 2005     

Impact‐modified polypropylene/vermiculite nanocomposites

Impact‐modified polypropylene (PP)/vermiculite (VMT) nanocomposites toughened with maleated styrene–ethylene butylene–styrene (SEBS‐g‐MA) were compounded in a twin‐screw extruder and injection‐molded. VMT was treated with maleic anhydride, which acted both as a compatibilizer for the polymeric matrices and as a swelling agent for VMT in the nanocomposites. The effects of the impact modifier on the morphology and the impact, static, and dynamic mechanical properties of the PP/VMT nanocomposites were investigated. Transmission electron microscopy revealed that an exfoliated VMT silicate layer structure was formed in ternary (PP–SEBS‐g‐MA)/VMT nanocomposites. Tensile tests showed that the styrene–ethylene butylene–styrene additions improved the tensile ductility of the (PP–SEBS‐g‐MA)/VMT ternary nanocomposites at the expense of their tensile stiffness and strength. Moreover, Izod impact measurements indicated that the SEBS‐g‐MA addition led to a significant improvement in the impact strength of the nanocomposites. The SEBS‐g‐MA elastomer was found to be very effective at converting brittle PP/VMT organoclay composites into tough nanocomposites. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2332–2341, 2003     

Impact‐specific essential work of fracture of maleic anhydride‐compatibilized polypropylene/elastomer blends and their composites

Charpy drop‐weight‐impact and essential work of fracture (EWF) characteristics of maleic anhydride (MA)‐compatibilized styrene–ethylene butylene–styrene (SEBS)/polypropylene (PP) blends and their composites reinforced with short glass fibers (SGFs) were investigated. MA was grafted to either SEBS copolymer (SEBS‐g‐MA) or PP (PP‐g‐MA). The mPP blend was prepared by the compounding of 95% PP and 5% PP‐g‐MA. Drop‐weight‐impact results revealed that the mPP specimen had an extremely low impact strength. The incorporation of SEBS or SEBS‐g‐MA elastomers into mPP improved its impact strength dramatically. Similarly, the addition of SEBS was beneficial for enhancing the impact strength of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids. A scanning electron microscopy examination of the fractured surfaces of impact specimens revealed that the glass‐fiber surfaces of the SGF/SEBS/mPP and SGF/SEBS‐g‐MA/mPP hybrids were sheathed completely with deformed matrix material. This was due to strong interfacial bonding between the phase components of the hybrids associated with the MA addition. Impact EWF tests were carried out on single‐edge‐notched‐bending specimens at 3 m s^?1. The results showed that pure PP, mPP, and the composites only exhibited specific essential work. The nonessential work was absent in these specimens under a high‐impact‐rate loading condition. The addition of SEBS or SEBS‐g‐MA elastomer to mPP increased both the specific essential and nonessential work of fracture. This implied that elastomer particles contributed to the dissipation of energy at the fracture surface and in the outer plastic zone at a high impact speed of 3 m s^?1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1881–1892, 2002     

Extruder‐made TPO nanocomposites. I. Effect of maleated polypropylene and organoclay ratio on the morphology and mechanical properties

PP/PP‐g‐MA/MMT/EOR blend nanocomposites were prepared in a twin‐screw extruder at fixed 30 wt % elastomer and 0 to 7 wt % MMT content. Elastomer particle size and shape in the presence of MMT were evaluated at various PP‐g‐MA/organoclay masterbatch ratios of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by maleated polypropylene serves to reduce the size of the elastomer dispersed phase particles and facilitates toughening of these blend nanocomposites. The rheological data analysis using modified Carreau‐Yasuda model showed maximum yield stress in extruder‐made nanocomposites compared with nanocomposites of reactor‐made TPO. Increasing either MMT content or the PP‐g‐MA/organoclay ratio can drive the elastomer particle size below the critical particle size below which toughness is dramatically increased. The ductile‐brittle transition shift toward lower MMT content as the PP‐g‐MA/organoclay ratio is increased. The D‐B transition temperature also decreased with increased MMT content and masterbatch ratio. Elastomer particle sizes below ～1.0 μm did not lead to further decrease in the D‐B transition temperature. The tensile modulus, yield strength, and elongation at yield improved with increasing MMT content and masterbatch ratio while elongation at break was reduced. The modified Mori‐Tanaka model showed better fit to experimental modulus when the effect of MMT and elastomer are considered individually. Overall, extruder‐made nanocomposites showed balanced properties of PP/PP‐g‐MA/MMT/EOR blend nanocomposites compared with nanocomposites of reactor‐made TPO. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Structural and mechanical behavior of polypropylene/ maleated styrene‐(ethylene‐co‐butylene)‐styrene/sisal fiber composites prepared by injection molding

Hybrid composites consisting of isotactic poly(propylene) (PP), sisal fiber (SF), and maleic anhydride grafted styrene‐(ethylene‐co‐butylene)‐styrene copolymer (MA‐SEBS) were prepared by melt compounding, followed by injection molding. The melt‐compounding torque behavior, thermal properties, morphology, crystal structure, and mechanical behavior of the PP/MA‐SEBS/SF composites were systematically investigated. The torque test, thermogravimetric analysis, differential scanning calorimetric, and scanning electron microscopic results all indicated that MA‐SEBS was an effective compatibilizer for the PP/SF composites, and there was a synergism between MA‐SEBS and PP/SF in the thermal stability of the PP/MA‐SEBS/SF composites. Wide‐angle X‐ray diffraction analysis indicated that the α form and β form of the PP crystals coexisted in the PP/MA‐SEBS/SF composites. With the incorporation of MA‐SEBS, the relative amount of β‐form PP crystals decreased significantly. Mechanical tests showed that the tensile strength and impact toughness of the PP/SF composites were generally improved by the incorporation of MA‐SEBS. The instrumented drop‐weight dart‐impact test was also used to examine the impact‐fracture behavior of these composites. The results revealed that the maximum impact force (F_max), impact‐fracture energy (E_T), total impact duration (t_r), crack‐initiation time (t_init), and crack‐propagation time (t_prop) of the composites all tended to increase with an increasing MA‐SEBS content. From these results, the incorporation of MA‐SEBS into PP/SF composites can retard both the crack initiation and propagation phases of the impact‐fracture process. These prolonged the crack initiation and propagation time and increased the energy consumption during impact fracture, thereby leading to toughening of PP/MA‐SEBS/SF composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1214–1222, 2002     

Compatibilization level effects on the structure and mechanical properties of rubber‐modified polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organically modified montmorillonite clay (OMMT) nanocomposites (PNs) were modified with partially maleinized styrene–ethylene/butadiene–styrene triblock copolymers (SEBS) at three maleinization levels in an attempt to link in these materials high toughness with appropriate small‐strain and fracture tensile properties. OMMT stayed only in the PA6 matrix, and no preferential location in the matrix/rubber interphase was observed. The increased dispersed phase size upon the addition of OMMT was attributed to interactions between maleic anhydride (MA) functionalized SEBS and the surfactant of OMMT. The rubber particle size generally decreased when the MA content of SEBS increased, and this indicated compatibilization. The subsequent good adhesion led to tough nanocomposites across a wide range of both strain rates and fracture modes. As the critical interparticle distance (τ_c) decreased with the MA content, and the other parameters that could influence the surface‐to‐surface mean interparticle distance did not change, it is proposed that in these PNs higher adhesion leads to a smaller τ_c value. Finally, the presence in the matrix of a nanostructured clay makes the rubber content necessary for the toughness jump to increase and τ_c to decrease. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3611–3620, 2005     

Influence of SEBS-g-MA on morphology, mechanical, and thermal properties of PA6/PP/organoclay nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organically modified clay (organoclay) toughened with maleated styrene-ethylene-butylene-styrene (SEBS-g-MA) were prepared by melt compounding using co-rotating twin-screw extruder followed by injection molding. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to characterize the structure of the nanocomposites. The mechanical properties of the nanocomposites were determined by tensile, flexural, and notched Izod impact tests. The single edge notch three point bending test was used to evaluate the fracture toughness of SEBS-g-MA toughened PA6/PP nanocomposites. Thermal properties were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). XRD and TEM results indicated the formation of the exfoliated structure for the PA6/PP/organoclay nanocomposites with and without SEBS-g-MA. With the exception of stiffness and strength, the addition of SEBS-g-MA into the PA6/PP/organoclay nanocomposites increased ductility, impact strength and fracture toughness. The elongation at break and fracture toughness of PA6/PP blends and nanocomposites were increased with increasing the testing speed, whereas tensile strength was decreased. The increase in ductility and fracture toughness at high testing speed could be attributed to the thermal blunting mechanism in front of crack tip. DSC results revealed that the presence of SEBS-g-MA had negligible effect on the melting and crystallization behavior of the PA6/PP/organoclay nanocomposites. TGA results showed that the incorporation of SEBS-g-MA increased the thermal stability of the nanocomposite.     

Preparation and nonisothermal crystallization behavior of polyamide 6/montmorillonite nanocomposites

Polyamide 6 (PA6)/montmorillonite (MMT) nanocomposites were prepared via melt intercalation. The structure, mechanical properties, and nonisothermal crystallization kinetics of PA6/MMT nanocomposites were investigated by X‐ray diffraction (XRD), tensile and impact tests, and differential scanning calorimetry (DSC). Before melt compounding, MMT was treated with an organic surfactant agent. XRD traces showed that PA6 crystallizes exclusively in γ‐crystalline structure within the nanocomposites. Tensile measurements showed that the MMT additions are beneficial in improving the strength and the stiffness of PA6, at the expense of tensile ductility. Impact tests revealed that the impact strength of PA6/MMT nanocomposites tended to decrease with increasing MMT content. The nonisothermal crystallization DSC data were analyzed by Avrami, Ozawa, modified Avrami‐Ozawa, and Nedkov methods. The validity of these empirical equations on the nonisothermal crystallization process of PA6/MMT nanocomposites is discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2878–2891, 2004     

Effect of PPO‐g‐MA on structures and properties of PPO/PA6/short glass fiber composites

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6) blends were reactively compatibilized by maleic anhydride (MA) grafted PPO (PPO‐g‐MA) and reinforced by short glass fibers (SGF) via melt extrusion. An observation of the SGF‐polymer interface by scanning electronic microscope (SEM) together with etching techniques indicated that the PPO‐g‐MA played a decisive role in the adhesion of polymers to SGF. The rheological behavior was investigated by capillary rheometer, and the addition of PPO‐g‐MA, and SGF could increase the viscosity of the PPO/PA6 blends. The analysis of fiber orientation and distribution in the PPO/PA6/SGF composites showed PPO‐g‐MA favored to the random dispersion of SGF. The statistic analysis of SGF length showed that PPO‐g‐MA was helpful to maintain the fiber length during melt‐processing. For the composites at a given SGF content of 30 wt %, the addition of PPO‐g‐MA increased the tensile strength from 59.4 MPa to 97.1 MPa and increased SGF efficiency factor from 0.028 to 0.132. The experimental data were consistent with the theoretical predictions of the extension of Kelly‐Tyson model for tensile strength. The fracture toughness of the composites was investigated by single edge notch three‐point bending test. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2188–2197, 2009     

Microstructure and fracture behavior of semicrystalline polymer–clay nanocomposites

The relationships between the microstructure and the fracture behavior of three polymer/clay nanocomposites were studied. Two different polymer matrices were chosen, namely polyamide‐6 and polyethylene (compatibilized with PE‐g‐MA or PE‐g‐PEo), to reach very different clay dispersion states. The microstructure was characterized in terms of polymer crystallinity, orientation of the polymer crystalline lamellae, clay dispersion state, and orientation of the clay tactoids. The mechanical behavior was characterized by tensile tests. The essential work of fracture (EWF) concept was used to determine the fracture behavior of the nanocomposites. Both tensile and EWF tests were performed in two perpendicular directions, namely longitudinal and transversal. It is shown that the fracture behaviors of the matrices mainly depend on the polymer crystalline lamellae orientation. For the nanocomposites, the relationships between the matrix orientation, the clay dispersion states, the values of the EWF parameters (w_e and βw_p), and their anisotropy are discussed. The results show that the lower the average clay tactoid thickness, the lower is the decrease of fracture performance for the nanocomposite and the more consumed energy as longer the path of the crack. Besides, a linear dependence of the anisotropy of the EWF parameters of the nanocomposites on the average clay aspect ratio is found. The more exfoliated the structure is, the less pronounced the anisotropy of the EWF parameters. Interestingly, it is thought that the average clay aspect ratio is the parameter representing the clay dispersion state that governs the fracture anisotropy of the nanocomposites (as the elastic properties determined by tensile tests). © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1820–1836, 2008     

Effects of elastomer on morphology,flammability and rheological properties of HIPS/PS‐encapsulated Mg(OH)2 composites

The effects of elastomer type on morphology, flammability and rheological properties of high‐impact polystyrene/Mg(OH)₂ based on encapsulated by polystyrene have been investigated. The ternary composites characterized by cone calorimetry, horizontal burning rate, limiting oxygen index (LOI), rheology and SEM. Morphology was controlled using poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] triblock copolymer (SEBS) or the corresponding maleinated SEBS (SEBS‐g‐MA). As revealed by SEM observations, composites of HIPS/SEBS/Mg(OH)₂ exhibit separation of the filler and elastomer and good adhesion between SEBS and the filler, whereas composites of HIPS/SEBS‐g‐MA/Mg(OH)₂ exhibit encapsulation of the filler by SEBS‐g‐MA. The flame retardant and rheological properties of ternary composites were strongly dependent on microstructure. The rheological test showed that the composites with encapsulation structure exhibit a stronger solid‐like response at low frequency than those of the composites with separate dispersion structure. The combustion tests showed that the composites with encapsulation structure showed higher flame retardant properties than those of separate dispersion structure at optimum use level of SEBS‐g‐MA. However, with the increase of the content of SEBS‐g‐MA, the flame retardancy of the composite declined somewhat which can be explained that the SEBS‐g‐MA coating acts as a heat and mass transfer barrier due to the formation of encapsulation structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2023–2030, 2007     

The compatibilization effect of ethylene/styrene interpolymer on polystyrene/polyethylene blends

In this study, ethylene/styrene interpolymer (ESI) was used as compatibilizer for the blends of polystyrene (PS) and low‐density polyethylene (LDPE). The mechanical properties including impact, tensile properties, and morphology of the blends were investigated by means of uniaxial tension, instrumented falling‐weight impact measurements, and scanning electron microscopy. Impact measurements indicated that the impact strength of the blends increases slowly with LDPE content up to 40 wt %; thereafter, it increases sharply with increasing LDPE content. The impact energy of the LDPE‐rich blends exceeded that of pure LDPE, implying that the LDPE polymer can be further toughened by the incorporation of brittle PS minor phase in the presence of ESI. Tensile tests showed that the yield strength of the PS/LDPE/ESI blends decreases considerably with increasing LDPE content. However, the elongation at break of the blends tended to increase significantly with increasing LDPE content. The compatibilization efficiency of ESI and polystyrene‐hydrogenated butadiene‐polystyrene triblock copolymers (SEBS) for PS/LDPE 50/50 was further compared. Mechanical properties show that ESI is more effective to achieve a combination of LDPE toughness and PS rigidity than SEBS. The correlation between the impact property and morphology of the ESI‐compatibilized PS/LDPE blends is discussed. The excellent tensile ductility of the LDPE‐rich blends resulted from shield yielding of the matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2136–2146, 2007     

Poly(lactic acid)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer/sepiolite nanocomposites: Investigation of thermo‐mechanical and morphological properties

In this study, sepiolite nanoclay is used as reinforcing agent for poly(lactic acid) (PLA)/(styrene‐ethylene‐butylene‐styrene)‐g‐maleic anhydride copolymer (SEBS‐g‐MA) 90/10 (w/w) blend. Effects of sepiolite on thermal behavior, morphology, and thermomechanical properties of PLA/SEBS‐g‐MA blend were investigated. Differential scanning calorimetry results showed 7% improvement in crystallinity at 0.5 wt% of sepiolite. The nanocomposite exhibited approximately 36% increase in the tensile modulus and 17% increase in toughness as compared with the blend matrix at 0.5 and 2.5 wt% of sepiolite respectively. Field emission scanning electron microscopy and transmission electron microscopy images exhibited sepiolite‐induced morphological changes and dispersion of sepiolite in both PLA and SEBS‐g‐MA phases. Dynamic mechanical analysis and wide angle X‐ray diffraction present evidences in support of the reinforcing nature of sepiolite and phase interaction between the filler and the matrix. This study confirms that sepiolite can improve tensile modulus and toughness of PLA/SEBS‐g‐MA blend.     

Use of maleic anhydride compatibilization to improve toughness and other properties of polylactide blended with thermoplastic elastomers

Polylactide (PLA) being a very brittle biopolymer could be toughened by blending with thermoplastic elastomers such as thermoplastic polyurethane elastomer (TPU) and thermoplastic polyester elastomer (TPE); unfortunately, these blends are immiscible forming round domains in the PLA matrix. Therefore, the purpose of this study was to investigate the effects of using maleic anhydride (MA) compatibilization on the toughness and other properties of PLA blended with TPU and TPE. MA grafting on the PLA backbone (PLA‐g‐MA) was prepared separately by reactive extrusion and added during melt blending of PLA/thermoplastic elastomers. IR spectroscopy revealed that MA graft might interact with the functional groups present in the hard segments of TPU and TPE domains via primary chemical reactions, so that higher level of compatibilization could be obtained. SEM studies indicated that PLA‐g‐MA compatibilization also decreased the size of elastomeric domains leading to higher level of surface area for more interfacial interactions. Toughness tests revealed that Charpy impact toughness and fracture toughness (K_IC and G_IC) of inherently brittle PLA increased enormously when the blends were compatibilized with PLA‐g‐MA. For instance, G_IC fracture toughness of PLA increased as much as 166%. It was also observed that PLA‐g‐MA compatibilization resulted in no detrimental effects on the other mechanical and thermal properties of PLA blends. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced interfacial interaction by grafting carboxylated‐macromolecular chains on nanodiamond surfaces for epoxy‐based thermosets

A novel core‐shell‐structured carboxylated‐styrene butadiene rubber (XSBR)‐functionalized nanodiamond (ND‐XSBR) was synthesized and characterized. Epoxy (EP) nanocomposites toughened by pristine ND and ND‐XSBR were investigated and compared. The ND‐XSBR‐reinforced nanocomposite exhibited mechanical properties superior to those of the one filled by pristine ND. At a low‐filler loading, the ND‐XSBR exhibited an impressive toughening effect. The maximum flexural strength was shown when the filler loading was as low as 0.1 wt % for the EP/ND‐XSBR nanocomposite. Furthermore, enhanced fracture toughness and fracture energy were shown by surface functionalization, representing enhanced compatibility between the ND‐XSBR and EP matrix. The glass transition temperature (T_g) and storage modulus of the nanocomposites were studied, and the EP/ND‐XSBR0.1 nanocomposite exhibited the highest T_g owing to the stronger interfacial interaction. The EP/ND‐XSBR0.2 exhibited higher storage modulus and T_g than the EP/ND0.2, because the higher interfacial interaction can restrict the molecular mobility of the EP by the functionalized ND‐XSBR. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1890–1898     

Extraordinary mechanical behavior of exfoliated montmorillonite/polymer nanocomposite films cast from soap‐free emulsion polymerized latices

The exfoliated montmorillonite (MMT) nanoplatelets tended to re‐stack with each other after casting the MMT/poly(methylacrylate‐co‐methylmethacrylate) P(MA‐co‐MMA) latex solutions fabricated by soap‐free emulsion polymerization into films as revealed by X‐ray diffraction and transmission electron microscopy. As the content of MMT was increased from 0 to 20 wt %, the T_g measured by differential scanning calorimetry was slightly decreased from 19.2 to 17.2 °C, whereas that measured by dynamic mechanical analysis was increased from 22 to 32 °C, indicating that the local motion of polymer segments has been retarded by MMT nanoplatelets. Besides, the elongated elliptical voids appeared during stretching of 1 wt % MMT/P(MA‐co‐MMA) film to cracking also illustrated the pinning effect provided by the exfoliated MMT. As the content of MMT was increased more than 10 wt %, the mechanical behavior of MMT/P(MA‐co‐MMA) nanocomposite films was changed from ductile to brittle nature with significant increase of Young's modulus and tensile strength owing to the restacking of exfoliated MMT nanoplatelets. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1064–1069, 2010     

Maleic Anhydride Polyethylene Octene Elastomer Toughened Polyamide 6/Polypropylene Nanocomposites: Mechanical and Morphological Properties

A series of polyamide 6/polypropylene (PA6/PP) blends and nanocomposites containing 4 wt% of organophilic modified montmorillonite (MMT) were designed and prepared by melt compounding followed by injection molding. Maleic anhydride polyethylene octene elastomer (POEgMAH) was used as impact modifier as well as compatibilizer in the blend system. Three weight ratios of PA6/PP blends were prepared i.e. 80:20, 70:30, and 60:40. The mechanical properties of PA6/PP blends and nanocomposite were studied through flexural and impact properties. Scanning electron microscopy (SEM) was used to study the microstructure. The incorporation of 10 wt% POEgMAH into PA6/PP blends significantly increased the toughness with a corresponding reduction in strength and stiffness. However, on further addition of 4 wt% organoclay, the strength and modulus increased but with a sacrifice in impact strength. It was also found that the mechanical properties are a function of blend ratio with 70:30 PA6/PP having the highest impact strength, both for blends and nanocomposites. The morphological study revealed that within the blend ratio studied, the higher the PA6 content, the finer were the POEgMAH particles.     

Synthesis and characterization of organosoluble,thermoplastic elastomer/clay nanocomposites

We synthesized organosoluble, thermoplastic elastomer/clay nanocomposites by making a jelly like solution of ethylene vinyl acetate containing 28% vinyl acetate (EVA‐28) and blending it with organomodified montmorillonite. Sodium montmorillonite (Na⁺‐MMT) was made organophilic by the intercalation of dodecyl ammonium ions. X‐ray diffraction patterns of Na⁺‐MMT and its corresponding organomodified dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) showed an increase in the interlayer spacing from 11.94 to 15.78 Å. However, X‐ray diffraction patterns of the thermoplastic elastomer and its hybrids with organomodified clay contents up to 6 wt % exhibited the disappearance of basal reflection peaks within an angle range of 3–10°, supporting the formation of a delaminated configuration. A hybrid containing 8 wt % 12Me‐MMT revealed a small hump within an angle range of 5–6° because of the aggregation of silicate layers in the EVA‐28 matrix. A transmission electron microscopy image of the same hybrid showed 3–5‐nm 12Me‐MMT particles dispersed in the thermoplastic elastomer matrix; that is, it led to the formation of nanocomposites or molecular‐level composites with a delaminated configuration. The formation of nanocomposites was reflected through the unexpected improvement of thermal and mechanical properties; for example, the tensile strength of a nanocomposite containing only 4 wt % organophilic clay was doubled in comparison with that of pure EVA‐28, and the thermal stability of the same nanocomposite was higher by about 34 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2065–2072, 2002     

Extruder‐made TPO nanocomposites. II. Effect of maleated poly(propylene)/organoclay ratio on morphology and thermal expansion behavior

Coefficients of linear thermal expansion (CTE) for poly(propylene)/ poly(propylene)‐grafted‐maleic anhydride/montmorillonite ethylene‐co‐octene elastomer (PP/PP‐g‐MA/MMT/EOR) blend nanocomposites were determined as a function of MMT content and various PP‐g‐MA/organoclay masterbatch ratios. The nanocomposites were prepared in a twin‐screw extruder at a fixed 30 wt % elastomer, 0–7 wt % MMT content, and various PP‐g‐MA/organoclay ratio of 0, 0.5, 1.0, and 1.5. The organoclay dispersion facilitated by the maleated PP helps to reduce the size of the dispersed phase elastomer particles in the PP matrix. The elastomer particle size decreased significantly as the PP‐g‐MA/organoclay ratio and MMT content increased; the elastomer particles viewed // to flow direction (FD) are smaller and less deformed compared to those viewed // to transverse direction (TD). The elastomer particle shape based on the view along the three orthogonal directions of the injection molded sample is similar to a prolate ellipsoid. The CTE decreased significantly in the FD and TD, whereas a slight increase is observed in the normal direction in the presence of MMT and PP‐g‐MA. The Chow model based on a two population approach showed better fit to experimental CTE when the effect of MMT and elastomer are considered individually. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013 , 51, 952–965     

Fracture studies of polypropylene/nanoclay composite. Part I: Effect of loading rates on essential work of fracture

Polypropylene (PP)/Montmorillonite (MMT) nanoclay based composite was prepared by melt compounding with maleic anhydride grafted polypropylene (MA-g-PP) as a compatibilizer in a twin-screw extruder, and the test specimens were injection molded. Mechanical properties such as tensile modulus, flexural modulus, yield strength and maximum percent strains were measured for pure PP and PP based nanocomposite to establish the effect of clay platelet reinforcement. The fracture properties were measured by using the essential work of fracture (EWF) method. PP/clay nanocomposite shows 25% improvement in specific EWF compared to pure PP. The variation of EWF parameters with loading rate is discussed, whilst the mechanisms of fracture are considered in a subsequent paper.