Crystallization and orientation behaviors in isotactic polystyrene and poly(2,6-dimethylphenylene oxide) blends

The crystallization and orientation behavior in the miscible iPS/PPO blends were studied aiming at producing oriented materials consisting of iPS crystals and amorphous PPO chains. Oriented films of iPS/PPO blends were prepared by drawing the melt-quenched blend films. The films were heat-treated under constraint at the drawing temperature so as to crystallize the molecular chains of iPS in the oriented state. The crystallinity and the crystal orientation in the drawn annealed films were studied by the wide-angle X-ray diffraction (WAXD), and the orientation behaviors of molecular chains were analyzed by polarized FTIR spectroscopy. WAXD diagrams show the presence of the highly oriented crystalline structure of iPS in the drawn annealed films of pure iPS and iPS/PPO=7/3 blend. The polarized FTIR spectra of drawn annealed films suggest that the molecular orientation of the amorphous chains of PPO and iPS is markedly relaxed by the heat treatment, although the orientation of iPS with 3₁ helical structure was retained during the oriented crystallization. It was concluded that the drawn annealed samples of the iPS/PPO=7/3 blend consist of highly oriented iPS crystals and nearly isotropic amorphous materials. The mechanical properties of the oriented iPS/PPO blends were measured not only in the stretching direction but also perpendicular to the stretching direction. It was shown that the ultimate strength in the perpendicular direction is 4-5 times higher in the drawn annealed film of iPS/PPO=7/3 blend than in the drawn annealed iPS. The improvement in the vertical strength in the blend is discussed in relation to the structural characteristics of the iPS/PPO blend.     

Unique orientation textures formed in miscible blends of poly(vinylidene fluoride) and poly[(R)-3-hydroxybutyrate]

The oriented crystallization of poly[(R)-3-hydroxybutyrate] (PHB) in the miscible blends with poly(vinylidene fluoride) (PVDF) was investigated with various compositions. The PVDF/PHB blend films were prepared by solution casting and subsequent melt-quenching in ice water. Oriented films of the blends were prepared by uniaxially stretching the melt-quenched film at 0 °C in ice water using a hand-operated stretching apparatus. The oriented blend films were heat-treated at a fixed length in order to crystallize PHB in the oriented state. The crystal orientation and the lamellar textures of the obtained samples were studied with wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS), respectively. The SAXS measurements showed that a considerable amount of molecular chains of PHB are excluded from the lamellar stacks of PVDF and exist in the interfibrillar regions in the oriented films of the blends. The cold crystallization of PHB in the interfibrillar region results in the orientation of PHB crystals, and the type of crystal orientation depends upon the composition of the blends. For the PVDF/PHB=4/6-7/3 blends, the crystal a-axis of PHB is highly oriented parallel to the drawing direction and the crystal c-axis (molecular chain axis) in PHB crystals is perpendicular to the drawing direction, i.e. orthogonal to the chain axis of the crystals of PVDF. It is considered that the a-axis orientation is induced by the confinement of crystal growth in the interfibrillar nano-domains. For the PVDF/PHB=2/8-3/7 blends, however, the crystal c-axis of PHB is primarily oriented in the drawing direction, suggesting that the stressed molecular chains of PHB are crystallized with the molecular orientation retained.     

Crystallization and orientation behaviors of poly(vinylidene fluoride) in the oriented blend with nylon 11

Oriented films of nylon 11/poly(vinylidene fluoride) (PVDF) blend were prepared by uniaxially stretching the melt-mixed blends. The drawn films of fixed length were heat-treated at 170 °C for 5 min to melt the PVDF component, followed by quenching in ice water or isothermal crystallization at various temperatures. The crystal forms and orientation textures of the obtained samples were studied using wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). It was found that PVDF can crystallize into both and β forms in the nylon 11/PVDF blends, and that the content of the β form increases with increasing crystallization temperature above 120 °C. The orientation behavior of the -form PVDF was observed to be dependent on the crystallization conditions: c-axis orientation to the stretching direction was produced for the sample crystallized below 50 °C; the a-axis of crystals was tilted from the stretching direction when PVDF was crystallized at about 75 °C; the parallel orientation of the a-axis to the stretching direction becomes dominant at higher crystallization temperatures (above 100 °C). In contrast, the β crystalline form maintains the c-axis orientation irrespective of crystallization temperature. It was shown by the confocal laser scanning microscopy that cylindrical domains of PVDF were dispersed in the oriented matrix of nylon 11. The mechanism for the formation of the unique orientation textures is discussed in detail. It was proposed that the a-axis orientation is a result of the trans-crystallization of PVDF in the cylindrical domains confined by the oriented matrix of nylon 11. The crystallization kinetics, WAXD analysis, and morphology studies preferred the trans-crystallization mechanism. The mechanical properties of the as-drawn and heat-treated samples were measured not only in the stretching direction but also in the direction perpendicular to it. It was found that the heat-treated samples show slightly lower tensile strength, but more elongation at the break in the two directions than the as-drawn samples.     

Structure and mechanical properties of uniaxially oriented films of syndiotactic polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends

The structure and mechanical properties of highly oriented films of a miscible blend of syndiotactic polystyrene and poly(2,6‐dimethylphenylene‐1,4‐oxide) (sPS/PPO) were studied in the composition range of sPS/PPO = 10/0 to 5/5. The oriented films were prepared by stretching the amorphous films of the blends. Wide‐angle X‐ray diffraction and polarized FTIR spectroscopy were used to analyze the amount of mesophase and molecular orientation. Drawing of the amorphous films of sPS and sPS/PPO blend induced a highly oriented mesophase. The mesophase content increases with increasing draw ratio and becomes nearly constant above a draw ratio of 3. Under the same draw ratio, the mesophase content decreases with increasing PPO content. The orientation function in the mesophase is as high as 0.95–0.99 irrespective of the composition and draw ratio. On the other hand, the orientation of molecular chains in the amorphous phase and mesophase increases with increasing draw ratio, and it decreases with increasing PPO content. The drawn films of pure sPS show high strength and high modulus in the drawing direction, but exhibit low strength in the direction perpendicular to the drawing. In the case of sPS/PPO = 7/3 blend, however, the ultimate strength in the perpendicular direction was dramatically improved compared with that of pure sPS and the ultimate strength in the parallel direction was similar to that for the oriented pure sPS. The improved mechanical properties in the sPS/PPO blends were discussed in relation to the structural characteristics of the sPS/PPO blend system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:2789–2797, 2004     

Micro-phase separation and crystallization behavior of amorphous oriented PLLA/PVAc blends during heat treatment under strain

Amorphous oriented poly(l-lactide) (PLLA)/poly(vinyl acetate) (PVAc) 50/50 films were prepared by uniaxial drawing of melt-mixed blends at 65 °C. The morphology development and crystal organization of the blends during heat treatment under strain were investigated using small angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). Equatorial scattering maxima in the SAXS patterns for samples annealed at 75 °C were observed before the appearance of crystal reflections. Further annealing of the samples at higher temperature induced two further discrete meridian scattering maxima. The observations indicated that homogenous oriented PLLA/PVAc film undergoes micro-phase separation first, followed by crystallization of PLLA in the PLLA-rich phase. The micro-phase separated PVAc nanodomains are aligned parallel to the stretching direction, whereas the crystallized PLLA lamellae are oriented perpendicular to the stretching direction (crystal c-axis along the stretching direction). Micro-phase separation was not observed when films were annealed at 120 °C, at which temperature the high crystallization rate of PLLA overwhelmed the micro-phase separation process.     

Nanolayer enhancement of biaxially oriented polypropylene film for increased gas barrier

An order of magnitude improvement in the oxygen barrier of biaxially oriented polypropylene (BOPP) films was achieved using a layer-multiplying, forced assembly process. The improvement was achieved without sacrificing clarity and toughness of the films. Sheets with 33 alternating layers of polypropylene (PP) (17 layers) and poly(?-caprolactone) (PCL) (16 layers) were coextruded using layer-multiplication and two thick PP skins were added to the multilayered core as the last step in the continuous coextrusion process. The sheets were subsequently biaxially oriented to draw ratios from 4 × 4 to 6 × 6. Biaxial orientation at elevated temperature reduced the thickness of the melted PCL layers from the microscale to the nanoscale, which created 2-dimensional confinement for subsequent crystallization of the PCL layers. It was anticipated that the PCL layers would recrystallize as highly oriented, in-plane lamellae that would resemble single crystals. However, the PCL lamellae were oriented perpendicular to the film surface, which actually facilitated oxygen permeation through the PCL layers and increased the oxygen permeability of the oriented films. Crystallization as on-edge lamellae was attributed to nucleation by the polypropylene surface. However, the surface nucleation was prevented by inserting buffer polystyrene (PS) layers in between the PCL and PP layers. In this case, the PCL lamellae were oriented in-plane. With the very high aspect ratio lamellar crystals oriented perpendicular to the flux direction, the permeation pathway of oxygen became very tortuous and the oxygen barrier was significantly improved.     

Structure of blown films of polyethylene/polybutene‐1 blends

The structure of blown films of blends of low‐density polyethylene (PE‐LD) and isotactic polybutene‐1 (iPB‐1) with different content of iPB‐1 was investigated using wide‐ and small‐angle X‐ray scattering (WAXS and SAXS), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). TEM proves formation of a matrix–particle phase structure due to immiscibility of the blend components. Within the iPB‐1 particles, needle‐like crystals with c‐axis orientation were observed. The PE‐LD matrix showed two populations of crystals. WAXS data indicate that the majority of crystals were oriented with the c‐axis perpendicular to machine direction (MD), while SAXS data prove additional presence of stacks of lamellae, oriented parallel to MD. Quantitative birefringence measurements showed that the majority of molecule segments were oriented in the direction of the circumference of the film, confirming the WAXS data. The crystal orientation has direct impact on mechanical properties, which was demonstrated by measurement of the anisotropy of the modulus of elasticity. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Surface structure,topology, and liquid wetting behavior in oriented polymers

The structure and the properties of oriented polymer surfaces were studied for three series of uniaxially oriented films of polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET). The surface structure was characterized in terms of relative crystallinity and molecular orientation along with topology and roughness by using FT-IR-ATR dichroism technique, optical microscopy and surface profilometer. In all three polymers, the surface orientation function increases with draw ratio. The relative surface crystallinity and the trans con-former also increases for PP and PET, respectively. In uniaxially drawn PP, the surface becomes rough with increasing draw ratio and the roughness is anisotropic with peaks and valleys elongated along the draw direction. For drawn PP, the equilibrium contact angles for four different liquids all exhibit anisotropy with higher values in perpendicular direction than that in parallel to the draw direction. In contrast, both drawn PET and PS films show smooth surfaces, and the equilibrium contact angles were all isotropic. When roughness is removed from the drawn PP by polishing without altering the molecular orientation, the anisotropy becomes negligible and the contact angles approach the value for undrawn PP. When surface roughness was created deliberately on undrawn PET and PS films, the contact angle anisotropy was clearly observed. Therefore, the anisotropy in surface topology rather than the molecular orientation seems to play a dominant role in developing anisotropic wetting behavior. The equilibrium contact angles for smooth surfaces have been calculated using the experimentally obtained roughness and anisotropic contact angle data from the rough surface. These values are in reasonable agreement with the measured contact angles for smooth surfaces, suggesting that the observed contact angle anisotropy can be attributed entirely to the roughness anisotropy rather than to the molecular orientation.     

Temperature dependence of crystalline transition of highly-oriented poly(l-lactide)/poly(d-lactide) blend: In-situ synchrotron X-ray scattering study

Formation of stereocomplex crystals (sc-crystals) of poly(l-lactide)/poly(d-lactide) (PLLA/PDLA) blend has been recognized as a unique opportunity to dramatically improve the heat-resistant of poly(lactic acid) (PLA). In this study, we investigated the dynamic formation and transition of sc-crystals in PLLA/PDLA drawn film with a combination of in-situ synchrotron wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). The correlation between sc-crystals content and the competing formation of α crystals (stable phase of PLA) in homopolymers during continuous heating and cooling processes was also studied. It was found that at room temperature, the original PLLA/PDLA drawn film consisted of only α crystals, however, with temperature increasing, two populations of sc-crystals were formed at different temperatures from the oriented amorphous region and the molten α crystals in the highly-oriented sample, respectively. Furthermore, new types of sc-crystals and α crystals with the orientation perpendicular to the original sc-crystals were formed during subsequent cooling process. On the basis of the X-ray scattering and DSC data, a schematic model for crystallization and oriented variation concerning sc-crystals and α crystals was proposed.     

Crystallization of linear low density polyethylene under two-dimensional confinement in high barrier blend systems

Blends of linear low density polyethylene (LLDPE) and ethylene vinyl alcohol (EVOH) with different weight fractions are extruded to fabricate thin films. The extruded blend film morphology is investigated by atomic force microscopy (AFM). The extruded blend films have shown extended morphology along the extrusion direction (ED) and dispersed morphology along the transverse direction (TD). We report that due to this morphology, a two-dimensional (2-D) confined crystallization occurs. The EVOH has successfully confined the LLDPE from both film normal direction (ND) and transverse direction (TD) in this study. The confinement from ND results in an on-edge orientation of LLDPE, while the confinement from TD forces the on-edge oriented LLDPE crystals to further elongate and extend along the extrusion direction (ED). This specific crystal orientation is different from one-dimensional (1-D) confined crystallization observed in multilayered films. Both wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) are utilized to investigate the crystal orientations of LLDPE in the extruded blend films. Moreover, due to the morphology, the extruded blend films have shown high oxygen barrier properties, which make this material valuable in packaging applications.     

Fracture behavior of die‐drawn toughened polypropylenes

The Leeds die‐drawing process has been used to make oriented sheets of toughened polypropylenes. Die‐drawn oriented sheets were produced by drawing at 110°C to draw ratios of 4, 6, and 10. Comparative measurements have been undertaken of the plane stress fracture toughness at room temperature using the essential work of fracture method for isotropic and oriented polypropylene homopolymer and the two polypropylene blends containing 10 and 25% of a polyethylene‐based elastomer. In the isotropic state, the blend containing 25% elastomer exhibited higher fracture toughness than the homopolymer and the 10% blend. The oriented sheets were tested both parallel (cracks perpendicular to the draw direction) and perpendicular (cracks parallel to the draw direction). For the latter case of cracks parallel to the draw direction, the fracture toughness of all the materials decreased with increasing draw ratio and up to a draw ratio of 4 the 25% blend exhibited higher fracture toughness than the other two materials. At higher draw ratios, however, the unfilled polypropylene was tougher than the blends. When tested parallel to the draw direction, all three materials failed with the cracks growing slowly initially followed by sudden rupture. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1336–1345, 2003     

Roll-drawing and die-drawing of toughened poly(ethylene terephthalate). Part 2. Fracture behaviour

Orientation of polymers in the solid-state has been used for a long time in enhancing the properties of the products and the die-drawing process at Leeds University (UK) and the roll-drawing process at IMI (Canada) have been used to produce oriented polymer products in a wide variety of shape and sizes. In this work, we explore the fracture behaviour of isotropic and oriented toughened poly(ethylene terephthalate) (PET) in order to improve the toughness of the oriented products in a direction other than the principal draw direction.The fracture behaviour of isotropic and oriented PET homopolymer and the two PET blends (containing 10% polyethylene elastomer and 10% compatibilized elastomer) was studied using the multi-specimen J-integral approach. In the isotropic case, the compatibilized blend had higher toughness than the homopolymer and the non-compatibilized blend. The oriented sheets from the die-drawing and roll-drawing process, drawn to a draw ratio of 3.2 at 170 °C were tested with the initial notch both parallel and perpendicular to the draw direction. For the former case, the compatibilized blend was tougher and in the other direction the drawn homopolymer was tougher than the blends. At similar draw ratios, the fracture behaviour and the toughness of the oriented sheets from the die-drawing and roll-drawing processes were identical.     

Zone drawn NEW-TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer

In this work we report the effects of single stage zone drawing on the properties of NEW-TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW-TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW-TPI. Blends of NEW-TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW-TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone-drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW-TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.     

Study on poly(ethylene terephthalate)/polypropylene microfibrillar composites. II. Solid‐state drawing behavior

A (20/80) blend of poly(ethylene terephthalate)/polypropylene (PET/PP) was solid‐state drawn to enhance the molecular orientation of the PET microfibers. Effects of drawing temperature (23–140°C) and drawing speed (max. 1000 mm/min) on the morphology and draw ratio of the blend were studied and discussed based on the drawing behaviors of the pure polymers. In cold drawing, there seemed to be a critical drawing speed below which the natural draw ratios of the polymers remained constant, but above which the draw ratios first decreased slightly because of suppression of molecular relaxation and then increased because of breakage of highly strained molecules and disintegration of lamellar crystals into finer mosaic blocks. Macroscopically, the pure PP and the PET/PP composite extrudates gave similar draw ratios at the same speeds. SEM showed that the PET microfibers suffered a smaller elongation than the PP matrix and severe voiding occurred at the PET/PP interface. Furthermore, substantial fiber breakage occurred during cold drawing at speeds above 200 mm/min. In comparison, drawing at 100°C caused no obvious interfacial voiding and fiber breakage. Furthermore, the natural draw ratio of the blend was lower than that of the pure PP extrudate, indicating that the PET microfibers had constrained the deformation of the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1989–2000, 2004     

Effect of montmorillonite on orientation of drawn polypropylene films

Films of polypropylene/organically modified montmorillonite (PP/OMMT) nanocomposites were drawn at two different temperatures with various draw ratios. The effect of OMMT on the orientations of the crystalline and amorphous phases was studied using polarized infrared spectroscopy. It is found that OMMT layers always retard the orientation of the crystalline phase. The higher the OMMT loading, the stronger the retardance effect. In contrast, the effect of OMMT layers on the orientation of the amorphous phase depends on draw temperature and OMMT loading. A favorable effect on the orientation of the amorphous phase is observed at low OMMT loading and high draw temperature, but the retardance prevails at high OMMT loading and low draw temperature. The favorable effect on orientation at high draw temperature is attributed to the stabilization effect of OMMT layers on the conformation of amorphous PP chains. Such an effect was further verified by comparing the crystallization behavior and the morphologies of drawn PP and PP/OMMT films crystallized from 180°C. Memory effect is observed for crystallization of drawn PP/OMMT film, but it is not obvious for the drawn film of neat PP. Spherulites are formed for orientated neat PP films cooled from 180°C, but cylindrites are still formed after the drawn PP/OMMT films undergo melting at 180°C and recrystallization. The stabilization effect disappears at higher temperature (230°C). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Properties of uniaxially stretched polypropylene films

Polypropylene (PP) films have been prepared through two different cast extrusion processes: one using a machine direction orientation (MDO) unit and the other stretching the films at the die under high cooling conditions (lab unit). Films for two PP resins different in molecular structure have been prepared using both processing techniques. The effect of the resin structure and the processing conditions on the film properties has been examined. It was found that the MDO unit generated a highly oriented fibrillar crystalline structure with a distribution of elongated thick fibrils while extrusion under high cooling conditions generated an oriented row nucleated lamellar structure. The films showed distinctive tensile responses in stretching, with a strong solid‐elastic response for the oriented MDO films and a steady strain hardening after yielding for the sample obtained from lab unit cast extrusion. It was found that the strength in the transverse direction (TD) was particularly very low for the oriented MDO films made of the bimodal PP. The oxygen permeability was reduced with increasing draw ratio (DR) for the MDO films. The haze property for the MDO samples reduced to a plateau for DR up to 5 while clarity improved continuously with DR.     

TRANSCRYSTALLIZATION WITH REORIENTATION OF POLYETHYLENE IN A DRAWN PET/PE BLEND AS REVEALED BY WAXS OF SYNCHROTRON RADIATION

A cold drawn blend of poly(ethylene terephthalate) (PET) and polyethylene (PE) (50/50 by wt.) was investigated during heating, melting, and subsequent crystallization upon cooling of PE by means of wide-angle X-ray scattering (WAXS) of synchrotron radiation. Strong epitaxial effects of the highly oriented PET on the very first stages of non-isothermal crystallization of PE during cooling of the cold drawn blend from 160°C to room temperature were found. WAXS shows that transcrystalline PE layers are formed around the PET fibrils. Within these layers, the PE crystallites are partly oriented at 90° with respect to their initial orientation (draw direction).     

Microstructural Development of Uniaxial Stretched Anneal-Oriented Syndiotactic Polystyrene and its Blend with Poly (2,6-dimethyl-1,4-phenylene oxide): DSC,WAXD, SAXS and FTIR Studies

Studies have been done on strain-induced microstructure development in syndiotactic polystyrene (s-PS) and its blends with poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) in 70/30 and 50/50 compositions of stretched annealed samples. Wide-angle X-ray showed that crystal orientation is less in annealed blend samples compared to annealed pure s-PS for a higher draw ratio. It increases with annealing, and relaxation occurs after a certain annealing temperature at above 180° for both s-PS and s-PS/PPO 70/30 blends. No crystal orientation was observed in the blend of s-PS/PPO 50/50 stretched samples. Small angle X-ray scattering (SAXS) shows the inclusion of amorphous PPO chains in between s-PS crystals lamella. Fourier transform infrared (FTIR) spectroscopy shows that the s-PS molecular chain packing band at 905 cm^?1 is enhanced due to annealing in oriented samples and saturates to around 0.63. The crystal chain relaxation is lower than amorphous chains of s-PS. The molecular chains of amorphous PPO are less oriented into the blend matrix, whereas its relaxation is enhanced during heat treatment and reaches an optimum value after full relaxation. The different behaviors of orientation and relaxation of s-PS and PPO chains into the blend matrix produce superstructures.     

Physical modification of polypropylene. III. Novel morphology of polypropylene and poly(ethylene-co-vinyl alcohol) with epoxy blend fibers

In this study, the novel morphology of polypropylene (PP) and poly(ethylene-co-vinyl alcohol) (EVOH) blend fibers is described. More precisely, the blend fibers of PP–EVOH containing a small amount of EVOH (1, 3, 5, 7, and 9% by weight), with and without epoxy (1 wt %), have been melt-spun at a constant spinning velocity (500 m/min). For the as-spun fiber, both the initial modulus and the tenacity increased with the increase in the EVOH content. The blend fibers with three draw ratios (2, 3, and 4) drawn at room temperature. The scanning electron microscopic study showed that a draw ratio of 2 reveals little about the morphological changes, whereas a draw ratio of 4 showed a streak structure perpendicular to the fiber axis for PP–EVOH (91/9 wt %) blend fibers. In addition, epoxy (1 wt %) containing PP–EVOH (91/9 wt %) blend fiber showed latitudinal streaks. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1049–1057, 1999     

Effect of poly(ethylene methyl acrylate) copolymer on thermal,morphological, and mechanical properties of polypropylene copolymer blown films

Blends of polypropylene copolymer (PP‐cp) and poly(ethylene methyl acrylate) [poly(EMA)] copolymer blends were processed by blown film extrusion. The orientation and crystallinity of PP‐cp matrix in the blend did not change significantly with the addition of EMA. The low machine direction and transverse direction tear strengths, which are observed for neat polypropylene blown films more than doubled at 6 wt % or higher content of EMA. The increase in tear properties was mainly attributed to a fine dispersion of EMA in the matrix with an average particle size of 100–500 nm and the formation of elongated domains. The dispersed nonrounded EMA domains, resulting from the blown‐film process, enhance better energy dissipation mechanism with the formation of an extended plastic zone in the blend films as compared with that in pure PP‐cp films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008