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Shear-induced crystallization behavior was studied using a phase-separated blend comprising a polypropylene continuous phase and a low-density polyethylene (LDPE) dispersion, which is known to show strain hardening in transient elongation viscosity. In this study, crystallization behavior was mainly evaluated by the light intensity transmitted through a transparent parallel-plate geometry. It was found that shear-induced crystallization was greatly accelerated by the addition of LDPE, resulting in a high crystallization temperature and a highly oriented structure. When the sample was cooled slowly, however, shear-induced crystallization was not accelerated by LDPE. Furthermore, extrusion was performed using a capillary rheometer. The molecular orientation in the strands collected after cooling in the air was found to be enhanced by the LDPE addition, suggesting that flow-induced crystallization was accelerated even at capillary extrusion. [ABSTRACT FROM AUTHOR]

α‐form crystalline isotactic polypropylene (PP) was prepared by two methods: quenching from the melt state at slow or high crystallization rates. The mechanical properties of the resulting PP samples were evaluated using tensile and stress–relaxation tests to investigate the influence of nodular or spherulite morphologies. PP samples with different morphologies had almost the same crystallinity after annealing at 100°C for 5 h. The yielding stress, strain‐hardening modulus, and strength of the nodular PP were higher than those of the spherulite PP, although the crystallinity was almost the same for both PP samples. Furthermore, the relaxation time during the stress–relaxation process at ε = 4.0 was longer for the nodular PP than for the spherulite PP. The lamellar structure of a spherulite morphology comprises parent and daughter lamellar crystals, whereas that of a nodular morphology prepared via a mesophase structure comprises only parent lamellar crystals. The formation of the daughter lamellae reduces the number of tie chains. Therefore, the nodular PP has more tie chains than the spherulite PP. This transformation from a spherulite to a nodular morphology improved the mechanical properties of the PP. Highlights: Influences of morphology on mechanical properties of polypropylene (PP).Tensile properties were higher for nodular PP than spherulite PP.Relaxation time of nodular PP was longer than spherulite PP.Nodular PP has more tie chains, resulting in improvements of tensile properties. [ABSTRACT FROM AUTHOR]

The rigidity of an injection‐molded isotactic polypropylene (PP) containing 1,3:2,4‐bis‐o‐(4‐methylbenzylidene)‐D‐sorbitol (MDBS) as a crystal nucleating agent can be enhanced by selection of appropriate processing conditions. A new method by differential scanning calorimetry measurements showed that the dissolution temperature of 0.4 wt.% MDBS in molten PP is around 210°C. When injection molding was performed below the dissolution temperature, for example, 190°C, the molecular orientation of PP was greatly enhanced. Although this is an anomalous condition for the system to expect good transparency, the product obtained showed a high flexural modulus. In contrast, with high‐temperature processing at 240°C, that is, conventional condition, the modulus decreased because of poor molecular orientation. Transmission electron microscopy observation revealed that MDBS fibrils strongly orient to the flow direction under the low‐temperature processing, in which network structure of MDBS fibers is not detected. The oriented MDBS fibers led to a well‐developed shish‐kebab structure, which is responsible for the pronounced rigidity. [ABSTRACT FROM AUTHOR]

In this study, polypropylene (PP) films containing the β nucleating agent, N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide, were prepared using PP with three different molecular weights (low, medium, and high) by extrusion process with T‐shaped die. The structure and morphology of the films were studied after stretching. It was found that a unique molecular orientation, in which both the c‐axis and crystalline lamellae were oriented perpendicular to the flow direction, was formed in all undrawn film samples, irrespective of the molecular weights of the PP. In the PP sheets stretched in the machine direction, the low‐molecular‐weight sample containing the nucleating agent exhibited brittle properties owing to a lack of tie chains in the stretching direction. In contrast, cavitation was prominent in the medium (M‐PP)‐ and high (H‐PP)‐molecular‐weight samples. Notably, M‐PP containing the nucleating agent, with a high degree of molecular orientation, promoted the formation of a large number of voids. In H‐PP containing the nucleating agent, the presence of numerous tie chains inhibited cavitation, resulting in fewer voids. The experimental results demonstrated the influence of the molecular weight on the void structure, which will be useful in the field of microporous membranes. [ABSTRACT FROM AUTHOR]

Adding polyethylene greatly affects the rheological response of isotactic polypropylene (PP) under uniaxial elongational flow. Though strain hardening in the transient elongational viscosity barely appeared in pure PP, we induced strain hardening by adding low-density polyethylene (LDPE) to PP, even though the blends showed a phase-separated structure. During elongational flow, LDPE droplets dispersed in the PP were deformed in the flow direction. Because LDPE shows marked strain hardening in the elongational viscosity, the deformed LDPE droplets behaved as rigid fibers as the strain increased. Consequently, the PP between the fibrous LDPE droplets experienced excess localized deformation, which increased the apparent elongational viscosity. Furthermore, adding the high-density polyethylene (HDPE) increased the drawdown force—defined as the force required for uniaxial stretching of a molten polymer in the nonisothermal condition. This behavior comes from the rapid crystallization of HDPE, which causes the deformed HDPE particles to act as rigid fibers in the molten PP and enhances the PP crystallization, which increases the elongational stress. [ABSTRACT FROM AUTHOR]

An extruded sheet having unique molecular orientation is developed using a miscible blend of isotactic polypropylene (PP) and isotactic polybutene-1 (PB). Blends containing a small amount of N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide are extruded from a ribbon-shaped die onto a chill roll at various temperatures. It is found that form-I crystals of PB become oriented in the flow direction, whereas β-form crystals of PP become oriented perpendicular to the flow direction. The molecular orientation is the most obvious for the blend containing 60 wt% of PB extruded at a chill roll temperature of 80 °C. The anisotropy in the tensile modulus of the obtained extruded sheet is reduced by its extraordinary molecular orientation. [ABSTRACT FROM AUTHOR]

ABSTRACT Drawdown force, defined as the force needed to stretch a polymer melt uniaxially at capillary extrusion, is investigated using isotactic polypropylene. In this study, we focus on the effect of die geometry on the drawdown force. As similar to the swell ratio, which decreases with increasing die length, the drawdown force is found to increase with the die length. A prolonged residence time in a long die leads to the marked orientation. Consequently, crystallization occurs rapidly after passing through a long die, which is confirmed by wide-angle X-ray measurements. Moreover, the rapid crystallization by the addition of a nucleating agent also enhances the drawdown force. [ABSTRACT FROM AUTHOR]

We evaluated the rigid–amorphous (RA) fraction of isotactic polypropylene (iPP) samples by various measurement techniques and investigated the role of the RA chains on the mechanical properties of iPP. The RA fraction was increased by annealing above the α -relaxation temperature, although the RA fraction was almost independent of the molecular weight. The RA fraction obtained by differential scanning calorimetry increased linearly with the number of consecutive helical chains with 12–14 monomer units, suggesting that the RA chains are attributable to crystalline defects. Moreover, the α -relaxation temperature varied linearly with the RA fraction; the RA chains present as crystalline defects were removed from the crystalline structure by α relaxation. The yielding region of the stress–strain curve became broad by increasing the RA fraction; the fragmentation strength of the lamellar crystals was widely distributed owing to the large number of crystalline defects. [Display omitted] • We evaluated the rigid–amorphous fraction of isotactic polypropylene. • A large number of rigid–amorphous chains were located in crystals as defects. • Rigid–amorphous chains are excluded from the crystals by annealing at 100 °C. • The yielding deformation broadened with increasing rigid–amorphous fraction. [ABSTRACT FROM AUTHOR]

The melting point of a conventional isotactic polypropylene (PP) was enhanced by a rapid annealing procedure of an extruded sheet composed of β trigonal form crystals having thick lamellae, which was prepared by T-die processing with a specific β-nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide. Although the melting point of PP with α monoclinic form, prepared by a conventional processing method, is known to be located around at 165°C, the sample obtained by the present technique showed a higher melting point, 170°C. The phase transformation from β-to α-form crystals, retaining the lamellar thickness, was responsible for the melting point elevation. [ABSTRACT FROM PUBLISHER]

Effect of the addition of poly(ethylene glycol) terminated by benzoate (PEG-BA) on the crystallization behavior and dynamic mechanical properties of poly( l-lactic acid) PLLA is studied as compared with poly(ethylene glycol) (PEG-OH). It is found that PEG-BA is miscible with PLLA and shows good plasticizing effect. Because PEG-OH having the same degree of polymerization is immiscible with PLLA, the end group in PEG-BA, i.e., benzoate, plays an important role in the miscibility. Furthermore, PEG-BA does not induce the PLLA degradation at melt-processing, whereas PEG-OH leads to the hydrolysis degradation. Finally, the addition of PEG-BA pronounces the crystallization rate of PLLA at low crystallization temperatures and thus enhances the degree of crystallinity at conventional processing. Consequently, the temperature dependence of dynamic mechanical properties are similar to that for isotactic polypropylene. [ABSTRACT FROM AUTHOR]

ABSTRACT The deformation behavior of a polypropylene (PP) sheet, in which c-axis of β-form PP orients perpendicular to the flow direction in the sheet [transverse direction (TD)], is studied focusing on the mechanical anisotropy. The deformation mechanism of this sample is found to be strongly dependent on the stretching direction. Shear yielding is dominant in TD stretching, indicating that reorganization and phase transformation of crystalline form occur easily with low yield stress. On the contrary, in machine direction (MD) stretching, numerous microvoids appear with the transformation of crystalline form as well as the rotation of c-axis. Moreover, the crazing process, initiated at the orientation defects, occurs locally with remaining undeformed region in which β-form PP orients to TD. The deformation behavior is applicable to a microporous film. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 897-906 [ABSTRACT FROM AUTHOR]

Morphology development of polytetrafluoroethylene (PTFE) caused by applied flow history in molten isotactic polypropylene (PP) is investigated, employing a cone-and- plate rheometer and a capillary rheometer as mixing devices. Since the flow history is applied at 190 °C, PTFE is in the solid state whereas PP is in the molten state. It is found that primary PTFE particles tend to be agglomerated together by mechanical interlocking. Then they are fragmented into fibers by hydrodynamic force with reorganization process of crystalline phase. The diameter of the fragmented fibers is the same as that of the original ellipsoidal particles. Further, fine fibers whose diameter is in the range from 50 to 100 nm are also generated by yielding behavior of the particles. The prolonged shearing leads to a large number of fibers, although the diameter and length are hardly affected by the exposure time of shearing and shear stress. Moreover, the flow type (i.e., drag or pressure flow) does not affect the morphology to a great extent, although the drag flow is not efficient to reduce large agglom- erated particles. The fibers form an interdigitated network structure, which is responsible for the marked melt elasticity. [ABSTRACT FROM AUTHOR]

Abstract: Injection-moulded products having unique structure, in which the direction of molecular orientation in the skin layer is perpendicular to that in the core layer, are developed employing isotactic polypropylene with a nucleating agent. The extraordinary three-layered structure with β trigonal crystal form in the core layer, which shows higher impact strength than the conventional α monoclinic form, leads to high level of toughness. Moreover, an injection-moulded product having five-layered structure is also demonstrated in this paper. Because of the complicated crack propagation nature due to the abrupt change of molecular orientation, which avoids fractured pieces with sharp-edge, the products with plywood-like structure will be employed in various applications to improve the safety. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the processability at extrusion coating and mechanical properties of the films obtained by means of linear and nonlinear rheological measurements and tensile tests for blends of polypropylene (PP) and linear low-density polyethylene (LLDPE). The study observed that there is an improvement in the processability of PP after the addition of LLDPE. It also found a reduced anisotropy of tensile strength by blending with LLDPE.

Abstract: Small amount of N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide as a β-form nucleating agent is dissolved beyond 280°C in a molten isotactic polypropylene (iPP) and appears as needle crystals around at 240°C during cooling procedure. Further, iPP molecules crystallize on the surface of the needle crystals, in which c-axis of the β-form iPP crystals grows perpendicular to the long axis of the needle crystals. Under flow field at extrusion processing, the needle crystals orient to the flow direction prior to the crystallization of iPP. As a result, c-axis of the β-form iPP crystals orients perpendicular to the applied flow direction with a small amount of α-form iPP. Moreover, the vertical molecular orientation of the extruded sheet sample is responsible for unique mechanical anisotropy; the fracture occurs along the transversal direction. [Copyright &y& Elsevier]

The effects of the ultra-high-molecular-weight (UHMW) component of polypropylene (PP) on its rheological properties, crystallization behavior, and solid-state mechanical properties were investigated using various measurement techniques. The terminal relaxation time—determined by measuring the linear viscoelasticity—was increased by adding the UHMW component. The increase in the melt elasticity produced by adding the UHMW component was observed by measuring the steady-state shear flow, although the shear viscosity was not greatly affected. Owing to the long characteristic time of the Rouse relaxation of the UHMW component, PP with the UHMW component formed highly oriented structures through a shear-induced crystallization process. The addition of the UHMW component enhanced the orientation and regularity of crystalline structure for extruded films. Therefore, the Young′s modulus, yield stress, and strength were higher in the PP film containing the UHMW component than in one without the UHMW component, irrespective of the direction of tensile deformation. [ABSTRACT FROM AUTHOR]

The article presents polymer engineering research into the properties and structure of injection-molded isotactic polypropylene with sorbitol-based clarifier. Results demonstrate that thinner injection-molded plaques of polypropylene/1,3:2,4-di-p-methylbenzylidene sorbitol (MDBS) have higher levels of transparency compared to compression-molded plaques. The network structure of the 1,3:2,4-di-p-methylbenzylidene sorbitol fibers in molten polypropylene depresses the spatial size of polarizability fluctuation in the core.

Abstract: The impact of applied processing history and the post-processing annealing procedure on the rheological properties of long-chain branched polypropylene (B-PP) have been studied intensively as compared with conventional linear polypropylene (L-PP) and low-density polyethylene (LDPE) produced by autoclave process. It was found that drawdown force, as a measure of melt elasticity for B-PP, is greatly depressed even by the short-time processing in an internal batch mixer, whereas the rheological properties of L-PP are unchanged by the processing history. Considering that the drawdown force is recovered to the original value during the post-processing annealing, the phenomenon is ascribed to the conformation change related to the branch structure, i.e. the alignment of long branches to a backbone chain, which is known as ‘shear modification’. Further, it is demonstrated that the depression of the drawdown force for B-PP is more significant than that for LDPE. Moreover, it is also clarified that B-PP needs a longer post-processing annealing time to recover the drawdown force than LDPE. The difference in the recovery curves during the annealing suggests that B-PP has less relatively ‘short’ long branches. [Copyright &y& Elsevier]

Presents information on a study which investigated the effects of morphology on mechanism of plastic deformation for binary blends of isotactic polypropylene and rubbery ethylene-1-hexene copolymers. Experimental details; Results and discussion; Conclusion.

We present a new method for the analysis of stress–strain curves for crystalline polymers such as polypropylene and polyethylene. A nonlinear constitutive equation that includes terms that cover the plastic deformation and anharmonicity of the spring is developed. In order to quantitatively characterize the nonlinear viscoelasticity using this equation, data on the transient moduli during elongation at a constant rate of strain are required. Hence, the simultaneous measurements of linear oscillatory viscoelastic moduli during a constant rate of elongation were investigated. It was found that the present method makes possible the evaluation of the plastic deformation fraction and the Gruneisen constant for crystalline polymers. © 1998 Chapman & Hall [ABSTRACT FROM AUTHOR]

The effects of neutralizer species on the transparency of injection-molded plates were studied using isotactic polypropylene (PP) containing a crystal nucleating agent—i.e., 1,3:2,4-bis-o-(4-methylbenzylidene)-d-sorbitol (MDBS). A plate containing lithium stearate (StLi) was more transparent than one containing calcium stearate (StCa) when the MDBS content was 0.1 wt. %. The addition of StLi accelerated the formation of MDBS fibers and the crystallization of PP. However, when the MDBS content was 1.0 wt. %, StCa improved the transparency more effectively than StLi. These results indicate that the combination of an appropriate amount of MDBS and the correct neutralizer species is critical for enhancing the transparency of injection-molded PP plates. [ABSTRACT FROM AUTHOR]

The shear-induced crystallization of polypropylene (PP) in immiscible blends with poly(methyl methacrylate) (PMMA) was studied using three types of PMMA samples with different molecular weights. The addition of low-molecular-weight PMMA greatly enhanced the shear-induced crystallization of PP. Because the low-molecular-weight PMMA had low viscosity at high temperatures, the PMMA droplets dispersed in the PP were deformed in the flow direction and subsequently turned fibrous. As the temperature decreased, the viscosity of PMMA increased greatly prior to PP crystallization. Consequently, the deformed PMMA dispersions were hardly deformed further in the molten PP. It provided excess stress for PP in the flow direction, leading to a large Rouse-Weissenberg number. They thereby accelerated shear-induced crystallization of the PP. Because of the pronounced shear-induced crystallization, the orientation of the PP chains, which causes high rigidity, was greatly enhanced. [Display omitted] • PMMA with low molecular weight promoted shear-induced crystallization of PP. • Deformed PMMA droplets solidified during cooling and acted as rigid fibers. • Because of pronounced shear-induced crystallization, PP orientation was enhanced. • PMMA with high molecular weight barely affected shear-induced crystallization of PP. [ABSTRACT FROM AUTHOR]

The effect of the nucleation efficiency of three commercial nucleating agents, such as 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS), sodium 2,2′‐methylene‐bis‐(4,6‐di‐tert‐butylphenyl)phosphate (SMBP), and magnesium silicate (talc), on the melt‐stretching performance of isotactic polypropylene (PP) is studied. It is found that the addition of 0.5 wt % of a nucleating agent enhances the crystallization temperature and that effect is pronounced for DMDBS and SMBP. Furthermore, DMDBS is more efficient than the other tested nucleating agents in enhancing the drawdown force, defined as a force required for stretching a molten strand. Nanofibers of DMDBS, which show significant alignment in the flow direction, are responsible for the rapid crystallization of PP in the flow field leading to an increase of drawdown force. The stretched strand shows a highly oriented structure in which the α‐form crystals orient to the flow direction. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47295. [ABSTRACT FROM AUTHOR]

The morphological transformation of extruded polypropylene (PP) films from the mesophase to α -form crystals has been investigated. Extruded PP films prepared by quenching had the mesophase morphology with a nearly-random orientation of the molecular chains. The mesophase structure of the quenched PP films completely transformed to α -form crystals by annealing at 100 °C accompanied by enhancement of the molecular orientation along the machining direction (MD). Moreover, the annealed films expanded and shrank by approximately 0.5% along the MD and transverse direction (TD), respectively. The unusual expansion behavior during annealing suggests that a small amount of oriented molecular chains formed in the extruded film, and the oriented chains acted as a nucleating agent. Consequently, the molecular orientation along the MD was enhanced owing to the morphological transformation. The oriented chains also acted as nucleating agent during tensile deformation, resulting in a significant improvement of strength in the MD stretching. [Display omitted] • We investigated the morphological transformation from mesophase to α -form crystals. • The molecular orientation was enhanced during the morphological transformation. • The extruded polypropylene films expanded in the MD after annealing. • Only a few oriented chains existing in the extruded films acted as nucleating agents. [ABSTRACT FROM AUTHOR]

A methodology for controlling the localization of multi-walled carbon nanotubes (MWCNTs) was studied using an immiscible polymer blend composed of isotactic polypropylene (PP) and ethylene- co -propylene rubber (EPR). We found that the MWCNTs were localized in EPR domains within the composite, which was prepared at 280 °C. EPR molecules bonded to the MWCNT surface are responsible for the localization in EPR. Conversely, MWCNTs preferentially resided in the matrix when the composite was prepared at 190 °C along with nitrogen gas purging. Because of the selective localization of the MWCNTs in the matrix, the composite obtained via mixing at the lower temperature exhibited a higher Young's modulus and yield strength. These findings demonstrate that mixing conditions greatly affect the MWCNT distribution and thus the mechanical properties of PP/EPR blends. [ABSTRACT FROM AUTHOR]

Abstract: A new method to localize polymer nanofibers on a polymer surface was verified using interface transfer technique of nanofibers between immiscible polymer pairs. Nanofibers of poly(butylene terephthalate) (PBT) were prepared in a molten polypropylene (PP) by melt-stretching and subsequent quenching. The obtained composite of PP containing PBT nanofibers was compressed into a flat sheet and piled with a sheet of high-density polyethylene (HDPE). During annealing procedure of the piled sheets at the temperature between melting points (Tm’s) of PP and PBT, PBT nanofibers were transferred from PP to HDPE. Consequently, PBT fibers was confirmed on the surface of HDPE. Similarly, polytetrafluoroethylene (PTFE) nanofibers dispersed in a molten poly(lactic acid) (PLA), which were obtained by mechanical blending process, were found to immigrate to PP during annealing procedure at the temperature between Tm’s of PLA and PTFE. This movement leads to the modification of surface tension for PP. Furthermore, the piled sheets of PP/PBT and HDPE as well as those of PLA/PTFE and PP were easily separated each other because of the immiscible nature. [Copyright &y& Elsevier]

Abstract: Imprinting of multi-walled carbon nanotubes (CNTs) on the surface of a polymer sheet was demonstrated using interphase CNT transfer from one polymer to another. A pure polycarbonate (PC) sheet was placed on top of a sheet of a polypropylene (PP)/CNT composite and annealed at either 200 or 300°C. It was found that CNTs move from the PP/CNT composite to the PC during annealing. The sheets of PP/CNT and PC were easily separated because of the large interfacial tension between PP and PC. The formation of a thin CNT-rich layer on the surface of the separated PC sheet produces electrical conductivity. Consequently, a conductive sheet is obtained with 2wt.% of CNTs only in the thin surface layer. Since the CNT transfer is attributed to Brownian motion, the annealing conditions such as temperature and time are responsible for the diffusion. The polymer species decides the ability of the CNTs to transfer. [Copyright &y& Elsevier]

The present paper describes a novel method for reinforcing isotactic polypropylene (PP) by adding poly(vinyl alcohol) (PVA) fibers prepared by melt-stretching. Low-viscosity PVA droplets were deformed into fibers in the molten PP by melt-stretching them beyond the melting point of PVA. When the obtained composite was extruded below the melting point of PVA, the fibers became oriented toward the flow direction. The PVA demonstrated marked nucleating activity with regard to PP crystallization, which was further promoted by enlargement of the surface area by fibrillization. As a result, there was virtually no orientation relaxation of the PP chains with an increase in crystallinity, which explains the improvement in rigidity of the reinforced composite. [Display omitted] • PVA fibers were well dispersed in PP by melt-mixing. • PVA fibers act as a nucleating agent for PP. • Chain orientation and crystallinity of PP were enhanced by the PVA addition. • Modulus of the extruded sample was enhanced by PVA fibers. [ABSTRACT FROM AUTHOR]

Abstract: An extruded polypropylene (PP) sheet in which both the chain-axes of the PP molecules and the crystalline lamellae are oriented perpendicular to the flow direction is obtained via row-nucleation on a specific needle-shaped nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide. The sheet shows anomalous anisotropy in dynamic tensile modulus, in which, at lower temperatures, the storage modulus in the machine direction (MD) is lower than that in the transverse direction (TD), and this behavior reverses at high temperature. Tensile tests reveal that the Young’s modulus and yield stress in the MD are higher than those in the TD. At high strain rate, the strain at break in the TD is, in contrast, markedly larger than that in the MD. [Copyright &y& Elsevier]

Poly (vinyl alcohol) (PVA) is immiscible with most conventional plastics and also unsuitable for melt processing owing to its extensive hydrogen bonding. Therefore, there have been few studies concerning the melt-mixing of PVA with standard plastics. The present paper describes a novel technique for producing isotactic polypropylene (PP) composites containing PVA fibers by directly introducing an aqueous solution of PVA into molten PP from an injection nozzle in a twin-screw extruder having a wide venting port. The PVA fibers were found to be dispersed homogeneously in the composites obtained by this method. Furthermore, an injection-molded product made from this composite exhibited an increased modulus, high yield strength, and high heat distortion temperature. These properties are attributed to the significant degree of orientation of both the PP chains and the PVA fibers. The nucleating action of the PVA fibers oriented in the flow direction is responsible for the structure of the composite, which in turn results in attractive properties. Image 1 • A polymer composite containing poly (vinyl alcohol) fibers was produced. • An aqueous solution of poly (vinyl alcohol) was injected into molten polypropylene. • A twin-screw extruder with a wide venting port was used. • Poly (vinyl alcohol) fibers and polypropylene were oriented after injection-molding. • Addition of poly (vinyl alcohol) enhanced mechanical properties of polypropylene. [ABSTRACT FROM AUTHOR]