Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends

The nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009     

Effects of functionalized multiwalled carbon nanotubes on the morphologies and mechanical properties of PP/EVA blend

The maleic anhydride‐grafted multiwalled carbon nanotubes (MWCNTs‐g‐MA) have been introduced into polypropylene/ethylene‐co‐vinyl acetate (PP/EVA) blend. To clearly describe the effects of MWCNTs‐g‐MA on the morphology and mechanical properties of PP/EVA blends, the selective distribution of MWCNTs‐g‐MA in the blends is realized through different sample preparation methods, namely, MWCNTs‐g‐MA disperse in EVA phase and MWCNTs‐g‐MA disperse in PP matrix. The results show that the distribution of MWCNTs‐g‐MA has an important effect on the final morphology of EVA and the crystallization structure of PP matrix. Compared with PP/EVA binary blend, distribution of MWCNTs‐g‐MA in PP matrix induces the aggregation of EVA phase at high EVA content and the decrease of spherulite diameters of PP matrix simultaneously. However, when MWCNTs‐g‐MA are dispersed in the EVA phase, they induce more homogeneous distribution of EVA, and the crystallization behavior of PP is slightly affected by MWCNTs‐g‐MA. The corresponding mechanical properties including impact strength and tensile strength are tested and analyzed in the work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1481–1491, 2009     

Selective distribution,reinforcement, and toughening roles of MWCNTs in immiscible polypropylene/ethylene‐co‐vinyl acetate blends

Polypropylene/ethylene‐co‐vinyl acetate (PP/EVA) nanocomposites with functionalized multiwalled carbon nanotubes (FMWCNTs) have been prepared. The dissolution experiment, transmission electronic microscope, and scanning electronic microscope characterizations prove that, in the nanocomposites with sea–island morphology, although some FMWCNTs are observed in both PP and EVA phases, most of FMWCNTs distribute at the interface; however, in the nanocomposites with cocontinuous morphology, FMWCNTs mainly distribute in EVA phase. Further results based on (differential scanning calorimetry) measurements show that the different dispersion states of FMWCNTs, which are resulted by the different melt blending sequences, result in the different crystallization behaviors of PP matrix. The mechanical measurements show that FMWCNTs exhibit apparent reinforcement and toughening effects for immiscible PP/EVA blends, and such effects are greatly dependent upon the blending sequences. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1882–1892, 2010     

Effects of nucleating agents on microstructure and fracture toughness of poly(propylene)/ethylene‐propylene‐diene terpolymer blends

The effects of nucleating agents (NAs) on fracture toughness of injection‐molded isotactic poly(propylene)/ethylene‐propylene‐diene terpolymer (PP/EPDM) were studied in this work. Compared with PP/EPDM blends without any NA, PP/EPDM/NA blends show very small and homogeneous PP spherulites. As we expected, PP/EPDM blends nucleated with β‐phase NA aryl amides compound (TMB‐5) present not only a significant enhancement in toughness but also a promotion of brittle‐ductile transition. However, the addition of α‐phase NA 1,3:2,4‐bis(3,4‐dimethylbenzylidene) sorbitol (DMDBS) has no apparent effect on the toughness of the blends. The impact‐fractured surface morphologies of such samples were analyzed via scanning electronic microscope (SEM). More detail work about the toughening mechanisms of elastomer and NA based on elastomer particles size and matrix crystal structures were carried out. Our results suggest that, besides the crystal structures of matrix, the elastomer particles size and size distribution plays an important role in controlling the toughening effect of nucleated PP/elastomer blends. The smaller the elastomer particles size and lower the polydispersity, the more apparent the synergistic toughening effect of NA and elastomer is. This investigation provides a fresh insight into the understanding of toughening mechanism of elastomers in PP blends and facilitates to the design of super toughened PP materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 46–59, 2009     

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     

Toughening effect of ethylene‐vinyl acetate rubber on nylon 1010 compatibilized by maleated ethylene‐vinyl acetate copolymers

The toughening effect of ethylene‐vinyl acetate rubbers (EVM) with maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) on the nylon 1010 was investigated. The addition of 5 phr (per hundred nylon 1010) EVM increased the elongation at break of nylon 1010 to a great extent. The notched Izod impact strength of nylon/EVM blends increased with increasing EVM content. Scanning electron microscope showed that the EVM particle size was around 0.5 μm when the EVM content was 5 phr and increased with increasing EVM content. After the addition of EVA‐g‐MAH to nylon/EVM (100/20) blend, the average diameter of EVM particles decreased from more than 1 μm to 0.5–0.6 μm. EVA‐g‐MAH could improve the adhesion between nylon 1010 and EVM. A sharp brittle‐ductile transition (BDT) was observed when the interparticle distance was about 0.2 μm, independent of the addition of EVA‐g‐MAH. The notched Izod impact strength of nylon/EVM blends at low temperatures was measured and the BDT shifted toward low temperatures with increasing EVM or EVA‐g‐MAH content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 434–444, 2009     

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     

Toughening of poly(L‐lactide)/multiwalled carbon nanotubes nanocomposite with ethylene‐co‐vinyl acetate

Poly(L ‐lactide)/multiwalled carbon nanotubes (PLLA/MWCNTs) nanocomposite recently attracts much attention because of its excellent comprehensive properties including improved thermostability, tensile strength, and conductivity. However, the nanocomposite exhibits similar brittleness compared with unmodified PLLA. In this work, a polar elastomer, that is, ethylene‐co‐vinyl acetate (EVA), was introduced into PLLA/MWCNTs nanocomposite. The selective distribution of MWCNTs and the effects of EVA on crystalline structure of PLLA were investigated using scanning electron microscope, transmission electron microscope, differential scanning calorimetry, and wide angle X‐ray diffraction. The results show that the presence of EVA induces the change of the distribution of MWCNTs in the nanocomposites, and consequently, the cold crystallization of PLLA is prevented. With the increase of EVA content, both the ductility and the impact resistance of PLLA/FMWCNTs are improved greatly, indicating the toughening effect of EVA on PLLA/MWCNTs nanocomposite. The decreased tensile strength and modulus can be compensated through annealing treatment. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Brittle–ductile transition of polypropylene/ethylene–propylene–diene monomer blends induced by size,temperature, and time

To study the brittle–ductile transition (BDT) of polypropylene (PP)/ethylene–propylene–diene monomer (EPDM) blends induced by size, temperature, and time, the toughness of the PP/EPDM blends was investigated over wide ranges of EPDM content, temperature, and strain rate. The toughness of the blends was determined from the tensile fracture energy of the side‐edge notched samples. The concept of interparticle distance (ID) was introduced into this study to probe the size effect on the BDT of PP/EPDM blends, whereas the effect of time corresponded to that of strain rate. The BDT induced by size, temperature, and time was observed in the fracture energy versus ID, temperature, and strain rate. The critical BDT temperatures for various EPDM contents at different initial strain rates were obtained from these transitions. The critical interparticle distance (ID_c) increased nonlinearly with increasing temperature, and when the initial strain rate was lower, the ID_c was larger. Moreover, the variation of the reciprocal of the initial strain rate with the reciprocal of temperature followed different straight lines for various EPDM contents. These straight lines were with the same slope. Furthermore, a diagram at critical BDT points in three dimensions (ID, T, and initial strain rate) was given for the PP/EPDM blends. The brittle and ductile zones are clearly shown in this diagram. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1433–1440, 2004     

Morphology and fracture behavior of toughening‐modified poly(vinyl chloride)/organophilic montmorillonite composites

Toughening‐modified poly(vinyl chloride) (PVC)/organophilic montmorillonite (OMMT) composites with an impact‐modifier resin (Blendex 338) were prepared by melt intercalation, and their microstructures were investigated with wide‐angle X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The mechanical properties of the PVC composites were examined in terms of the content of Blendex and OMMT, and the fracture toughness was analyzed with a modified essential work of fracture model. Intercalated structures were found in the PVC/OMMT composites with or without Blendex. Either Blendex or OMMT could improve the elongation at break and notched impact strength of PVC at proper contents. With the addition of 30 phr or more of Blendex, supertough behavior was observed for PVC/Blendex blends, and their notched impact strength was increased more than 3319% compared with that of pristine PVC. Furthermore, the addition of OMMT greatly improved both the toughness and strength of PVC/Blendex blends, and the toughening effect of OMMT on PVC/Blendex blends was much larger than that on pristine PVC. Blendex and OMMT synergistically improved the mechanical properties of PVC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 286–295, 2004     

Effect of nucleating agent on the brittle–ductile transition behavior of polypropylene/ethylene–octene copolymer blends

In the present work, α‐form nucleating agent 1,3:2,4‐bis (3,4‐dimethylbenzylidene) sorbitol (DMDBS, Millad 3988) is introduced into the blends of polypropylene/ethylene–octene copolymer (PP/POE) blends to study the effect of the nucleating agent on the toughness of PP/POE blends through affecting the crystallization behavior of PP matrix. Compared with the PP/POE blends, in which the toughness of the blends increases gradually with the increasing content of POE and only a weak transition in toughness is observed, addition of 0.2 wt % DMDBS induces not only the definitely brittle‐ductile transition at low POE content but also the enhancement of toughness and tensile strength of the blends simultaneously. Study on the morphologies of impact‐fractured surfaces suggests that the addition of a few amounts of DMDBS increases the degree of plastic deformation of sample during the fracture process. WAXD results suggest that POE induces the formation of the β‐form crystalline of PP; however, DMDBS prevents the formation of it. SEM results show that the addition of DMDBS does not affect the dispersion and phase morphologies of POE particles in PP matrix. DSC and POM results show that, although POE acts as a nucleating agent for PP crystallization and which enhances the crystallization temperature of PP and decreases the spherulites size of PP slightly, DMDBS induces the enhancement of the crystallization temperature of PP and the decrease of spherulites size of PP more greatly. It is concluded that the definitely brittle–ductile transition behavior during the impact process and the great improvement of toughness of the blends are attributed to the sharp decrease of PP spherulites size and their homogeneous distribution obtained by the addition of nucleating agent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 577–588, 2008     

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

Effect of dispersed phase composition on morphological and mechanical properties of PET/EVA/PP ternary blends

Immiscible ternary blends of PET/EVA/PP (PET as the matrix and (PP/EVA) composition ratio = 1/1) were prepared by melt mixing. Scanning electron microscope results showed core‐shell type morphology for this ternary blend. Binary blends of PET/PP and PET/EVA were also prepared as control samples. Two grades of EVA with various viscosities, one higher and the other one lower than that of PP, were used to investigate the effect of components' viscosity on the droplet size of disperse phase. The effect of interfacial tension, elasticity, and viscosity on the disperse phase size of both binary and ternary blends was investigated. Variation of tensile modulus of both binary and ternary blends with dispersed phase content was also studied. Experimental results obtained for modulus of PET/EVA binary blends, showed no significant deviations from Takayanagi model, where considerable deviations were observed for PET/PP binary blends. Here, this model that has been originally proposed for binary blends was improved to become applicable for the prediction of the tensile modulus of ternary blends. The new modified model showed good agreement with the experimental data obtained in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 251–259, 2010     

Influence of Phase Miscibility on the Crack Propagation Kinetics of Nanostructured Binary S‐(S/B)‐S Triblock Copolymer Blends

Summary: The crack propagation kinetics of binary styrene‐(styrene/butadiene)‐styrene triblock copolymer blends based on one with symmetrical (LN4) and another with asymmetrical (LN3) molecular architecture is discussed with respect to post‐yield crack‐tip blunting and stable crack propagation behavior while highlighting the dynamic mechanical properties of the blends. The crack‐tip opening displacement (CTOD) rate is revealed to be sensitive to phase behavior, which is in agreement with a transition in phase miscibility in a critical composition range of 40–60 wt.‐% of LN3. Analyses of R‐curves from CTOD‐values reveal that kinetics of crack propagation is controlled by phase behavior, whereas the resistance to stable crack initiation is largely dependent on the composition. Our investigation offers new possibilities to tailor and optimize the crack resistance (crack propagation stability) of block copolymer blends through the control of phase miscibility and hence, fundamentally, adds a new dimension to the development of novel materials based on toughened nanostructured polymers.

Crack resistance curves for LN3 blends having different compositions.     

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     

Uncross‐linked polypropylene (PP)/ethylene‐propylene‐diene (EPDM)/multi walled carbon nanotube (MWCNT) and dynamically vulcanized PP/EPDM/MWCNT nanocomposites

In this study, relatively large amounts of polypropylene (PP), ethylene‐propylene‐diene (EPDM), and multi‐walled carbon nanotube (MWCNT) were melt‐mixed with and without DCP. Dynamically vulcanized PP/EPDM (TPV)/MWCNT nanocomposites were prepared by two methods: the MWCNTs were added either before or after the dynamic vulcanization of the blends. The effects of composition, rotor speed, and dynamic vulcanization on their surface resistivity were investigated. The surface resistivity of uncross‐linked PP/EPDM/MWCNT nanocomposites increases with increasing the content of EPDM. At PP/EPDM (70/30 wt%) nanocomposite with 1.5 phr MWCNT, slightly lower surface resistivity is obtained by increasing the rotor speed during mixing. However, for PP/EPDM (50/50 wt%) and PP/EPDM (30/70 wt%) nanocomposites, surface resistivity decreases with increasing the rotor speed from 30 to 60 rpm. But further increase in rotor speed (90 rpm) leads to an increase of surface resistivity. When the MWCNTs were added after the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNTnanocomposite is lower than that of uncross‐linked PP/EPDM/MWCNT nanocomposite. However, when the MWCNTs were added before the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNT nanocomposite is >10¹² Ω/square. Copyright © 2010 John Wiley & Sons, Ltd.     

Matrix‐polymer‐functionalized multiwalled carbon nanotubes as a highly efficient toughening agent for matrix polymers

Matrix‐polymer‐functionalized multiwalled carbon nanotubes (MWCNTs) are demonstrated as a highly efficient toughening agent for matrix polymers. With poly(vinylidene fluoride) (PVDF) as the matrix polymer, the PVDF/MWCNT‐PVDF nanocomposite films show high toughness. With a small load amount of MWCNT‐PVDF (0.07 wt %), the nanocomposite film shows a yield point and a constant‐stress extension region in stress–strain tests, compared with the typical low‐extensibility feature of neat PVDF film. The PVDF/MWCNT‐PVDF‐0.7 film exhibits a 180‐fold increase of toughness and about 38‐fold increase in strain at break compared with neat PVDF film. This toughening effect is attributed to (a) homogeneous dispersion of MWCNT‐PVDF in PVDF, (b) the high efficiency of load‐transfer across MWCNT/PVDF interface, and (c) the long length of the MWCNTs. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Fracture toughness of nylon‐6 blends with maleated rubbers

The fracture toughness of blends of nylon‐6 with maleated ethylene–propylene rubber and maleated styrene/hydrogenated butadiene/styrene triblock copolymer was investigated with a single‐edge‐notched three‐point‐bending instrumented Dynatup test. The blends for which the rubber particle size was less than 0.7 μm fractured in a ductile manner over the whole range of ligament lengths, whereas the blends with particles larger than 0.7 μm showed a ductile‐to‐brittle transition with the ligament length. In this regime, ductile fracture was observed for specimens with short ligaments, whereas brittle fracture was seen for those with long ligaments. The ductile fracture behavior was analyzed with the essential‐work‐of‐fracture model, whereas linear elastic fracture mechanics techniques were used to analyze the brittle fracture behavior. The fact that the ductile fracture energy was larger for the blends with the styrene/hydrogenated butadiene/styrene triblock copolymer than for those with ethylene–propylene rubber was due to the larger dissipative energy density of the blends based on the styrene/hydrogenated butadiene/styrene triblock copolymer. Both the critical strain energy release rate (G_IC) and the plane‐strain critical stress intensity factor (K_IC) increased as the rubber particle size decreased for both blend systems. The G_IC and K_IC parameters had similar values, regardless of the rubber type, when the rubber particle size was fixed. The transition ligament length was near the size criterion for plane‐strain conditions for both blend systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1739–1758, 2004     

Phase separation of off‐critical polymer blends of poly(styrene‐co‐maleic anhydride) and poly(methyl methacrylate). II. Morphology and mechanical properties

The effects of the phase‐separation temperature and time on the mechanical properties and morphology of poly(methyl methacrylate)/poly(styrene‐co‐maleic anhydride with 10 wt% ethyl acrylate) (SMA) blends were studied. Two compositions (20/80 and 40/60 w/w SMA/PMMAe) were prepared with a miniature twin‐screw extruder. Compared with those of the miscible blends, the Young's modulus values of the blends increased after the phase separation of the 40/60 SMA/PMMAe blend and within the early stage of spinodal decomposition of the 20/80 SMA/PMMAe blend. The mechanical properties, in terms of the tensile strength at break and the elongation, were better for the miscible blends than for the phase‐separation blends. This was believed to be the result of changes in the composition and molecular reorganization. The changes in the phase‐separating domains of both compositions, as observed by transmission electron microscopy, had no significant influence on the tensile moduli. Detailed studies of the morphology revealed a cocontinuous structure, indicating that the blends underwent spinodal decomposition. A morphological comparison of the two compositions illustrated the validity of the level rule. The growth rate of the droplet size was determined by approximation from the light scattering data and by direct measurements with transmission electron microscopy. The discrepancies observed in the droplet size growth rate were attributed to heat variations induced by the different sample thicknesses and heat transfer during the investigation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 886–897, 2004     

Preparation of fully cross‐linked CNBR/PP‐g‐GMA and CNBR/PP/PP‐g‐GMA thermoplastic elastomers and their morphology,structure and properties

Binary CNBR/PP‐g‐GMA and ternary CNBR/PP/PP‐g‐GMA thermoplastic elastomers were prepared by reactive blending carboxy nitrile rubber (CNBR) powder with nanometer dimension and polypropylene functionalized with glycidyl methacrylate (PP‐g‐GMA). Morphology observation by using an atomic force microscope (AFM) and TEM revealed that the size of CNBR dispersed phase in CNBR/PP‐g‐GMA binary blends was much smaller than that of the corresponding CNBR/PP binary blends. Thermal behavior of CNBR/PP‐g‐GMA and CNBR/PP blends was studied by DSC. Comparing with the plain PP‐g‐GMA, T_c of PP‐g‐GMA in CNBR/PP‐g‐GMA blends increased about 10 °C. Both thermodynamic and kinetic effects would influence the crystallization behavior of PP‐g‐GMA in CNBR/PP‐g‐GMA blends. At a fixed content of CNBR, the apparent viscosity of the blending system increased with increasing the content of PP‐g‐GMA. FTIR spectrum verified that the improvement of miscibility of CNBR and PP‐g‐GMA was originated from the reaction between carboxy end groups of CNBR and epoxy groups of GMA grafted onto PP molecular chains. Comparing with CNBR/PP blends, the tensile strength, stress at 100% strain, and elongation at break of CNBR/PP‐g‐GMA blends were greatly improved. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1042–1052, 2004