Syndiotactic polystyrene‐b‐atactic polypropylene block copolymer alloy as a compatibilizer for syndiotactic polystyrene/isotactic polypropylene blends

A polymeric alloy (SP–A) containing syndiotactic polystyrene (sPS), atactic polypropylene (aPP), and about 66 wt % sPS‐b‐aPP diblock copolymer, was prepared by the sequential feed of monomers in the presence of the half‐titanocene Cp*Ti(OBz)₃ (where Cp* is C₅Me₅ and Bz is PhCH₂), modified methylaluminoxane, and external triisobutylaluminum. The effects of the SP–A alloy as a compatibilizer for sPS and isotactic polypropylene (iPP) blends were evaluated. The blending of sPS and iPP, with and without SP–A, was performed in a single‐screw miniextruder with a side channel that allowed the continuous recycling of materials. The influence of SP–A on the mechanical and thermal properties of the immiscible sPS/iPP blends was investigated over a range of composition. The presence of the SP–A alloy resulted in a significant improvement of the impact strength of the blends compared with that of pure sPS and their pure blends. This improvement was particularly obvious in the sPS/iPP (90/10 wt %) blend containing 5 wt % SP–A. Morphological analysis of the impact‐fractured surface of the ternary blends indicated that the sPS‐b‐aPP diblock copolymer contained in the SP–A alloy acted as an efficient compatibilizer by decreasing the dispersed‐phase iPP particle size, improving the interfacial adhesion, and generating a stable microphase‐separated state. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1596–1605, 2003     

Morphology and mechanical properties of polypropylene/high‐impact polystyrene blends from postconsumer plastic waste

The compatibilizing effect of the triblock copolymer poly(styrene‐b‐ethylene‐co‐butylene‐b‐styrene) (SEBS) on the morphological and mechanical properties of virgin and recycled polypropylene (PP)/high‐impact polystyrene (HIPS) blends was studied, with the properties optimized for rigid composite films. The components of the blend were obtained from municipal plastic waste, PP being acquired from mineral water bottles (PP_b) and HIPS from disposable cups. These materials were preground, washed only with water, dried with hot air, and ground again (PP_b) or agglutinated (HIPS). Blends with three different weight ratios of PP_b and HIPS (6:1, 6:2, and 6:3) were prepared, and three different concentrations of SEBS (5, 6, and 7 wt %) were used for investigations of its compatibilizing effect. Scanning electron microscopy showed that SEBS reduced the diameter of dispersed HIPS particles in the globular and fibril shapes and improved the adhesion between the disperse phase and the matrix. However, SEBS interactions with PP_b and HIPS influenced the mechanical properties of the compatibilized PP_b/HIPS/SEBS blends. An adequate composition of PP/HIPS, for both virgin and recycled blends, for applications in composite films with characteristics similar to those of synthetic paper was obtained with a minimal amount of SEBS and a maximal HIPS/PP ratio in the range of concentrations studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2861–2867, 2003     

Characterization of the free volume in high‐impact polystyrene/polypropylene and high‐impact polystyrene/high‐density polyethylene blends probed by positron annihilation spectroscopy

The free‐volume properties of high‐impact polystyrene (HIPS)/polypropylene (PP) and HIPS/high‐density polyethylene (HDPE) blends were investigated by means of positron annihilation lifetime spectroscopy (PALS). The measured results show that the free‐volume holes in the semicrystalline polymers, such as PP and HDPE, were not large enough to accommodate the branched chains and the end groups of the macromolecular chains in HIPS to produce favorable interactions between the semicrystalline polymers and the HIPS polymer in these blends; thus immiscible blends were formed. The weak interaction between two dissimilar polymer molecules only took place in the regions between two amorphous phases. In addition, the observed negative deviations of the longest lifetime intensity and the free‐volume fraction were attributed to the influence of the interfacial polarization during PALS measurement. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1507–1514, 2003     

Additive effect of poly(ethylene oxide) on polypropylene/fibrous cellulose composite: Effects of additive amount of poly(ethylene oxide) on Young's modulus and morphology

In this work, the additive effects of the poly(ethylene oxide) (PEO) on the Young's moduli of two kinds of polypropylene (PP)/fibrous cellulose (FC) composite were studied using the Kerner–Nielsen equation. In the case of the PP/maleated PP (MAPP)/FC + PEO composite, all the values of the moduli with the various PEO contents were in good agreement with the theoretical values obtained from the Kerner–Nielsen equation. Whereas the moduli of the PEO/FC + PP/MAPP composite followed the Kerner–Nielsen equation about 6 vol % of the PEO content and then unexpectedly deviated. In the scanning electron microscopy (SEM) observation, the PP/MAPP/FC + PEO composite was found to have a sea‐island morphology corresponding to the PP/MAPP/FC matrix and the PEO phase. This morphology had been unchanged against the increase of the PEO content. Whereas in the case of the PEO/FC + PP/MAPP composite, the SEM micrographs showed that that the interface between the FC and the PP became worse with the increase of the PEO content, indicating that the formation of the PP/MAPP/FC matrix was blocked by the excess PEO. The deviation of the Young's moduli from the Kerner–Nielsen equation was due to the blocking of the PEO. It was found that the adequate combination of the PEO and the MAPP was able to supply the increase of the toughness of the PP/FC composite by investigating the dependence of the PEO/FC + PP/MAPP composite on the MAPP content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Striped‐pattern deterioration and morphological analysis of injection moldings comprising polypropylene/ethylene α‐olefin rubber blends. I. Influence of ultraviolet irradiation

Unique deterioration with a periodical striped pattern on the injection moldings of polypropylene/rubber blends is reported. After exposure to ultraviolet irradiation with a sunshine fade meter, striped patterns appeared on the injection moldings along the flow direction of the molten resin during the filling process of injection molding, even though the initial specimen showed no sign of any stripe pattern on its surface. The stripe was carefully observed with ultrasonic echo imaging, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. As a result, a number of microvoids were observed inside the injected body at a depth of 50–100 μm from the surface. It became clear that the difference in the number of voids along the flow direction formed the stripe pattern. Surprisingly, these voids occurred in domains comprising a rubber phase. The distribution of voids in depth indicated the existence of a trace of a snakelike flow caused inside the injected body during the injection‐molding process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effect of calcium carbonate on the mechanical and thermal properties of isotactic polypropylene/ethylene vinyl acetate blends

The effect of calcium carbonate (CaCO₃) on the mechanical properties (with heat treatment) and thermal properties of polypropylene and isotactic polypropylene (i‐PP)/ethylene vinyl acetate (EVA) blends was investigated. CaCO₃, in five different concentrations (3, 6, 9, 12l, and 15 wt %), was added to i‐PP/EVA (88/12) to produce ternary composites. The mechanical properties, including the yield and tensile strengths, elastic modulus, Izod impact strength for notch radii of 0.25 and 1 mm, and hardness with and without an annealing heat treatment, and the thermal properties, such as the melting point and melt‐flow index, of the composites were investigated. The annealing heat treatment was carried out at 100°C for three different holding times: 75, 100, and 150 h. On the basis of the results, attempts were made to establish a relationship between the CaCO₃ content, the annealing holding time, and the mechanical and thermal properties to obtain the best results. The tensile test results showed that the heat treatment was not effective for the ultimate tensile strength, and the yield strength and tensile strength decreased gradually as the CaCO₃ content increased. However, CaCO₃ was effective for higher elastic modulus, impact strength, and hardness values. A considerable increase in the elastic modulus was found with a 3% CaCO₃ concentration for a holding time of 100 h. The maximum impact strength for a notch radius of 1 mm was obtained with 3% CaCO₃ with annealing for a holding time of 100 h, whereas a 9% CaCO₃ concentration produced higher toughness values for a notch radius of 0.25 mm. The fracture surfaces also supported the results from the Izod impact tests. Similarly, hardness values increased with the annealing heat treatment and increasing CaCO₃ content. However, different holding times showed similar effects on the hardness values. The increased CaCO₃ content caused the melting point to increase 5°C, whereas the melt‐flow index showed a sharp decrease as the CaCO₃ content increased to 3%. Taking into consideration the mechanical and thermal properties and the annealing holding time, we recommend a CaCO₃ concentration of 3% with an annealing heat treatment for 100 h for optimum properties of such ternary composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1126–1137, 2005     

Improving polypropylene microcellular foaming through blending and the addition of nano‐calcium carbonate

This article reports an attempt to improve polypropylene (PP) microcellular foaming through the blending of PP with high‐density polyethylene (HDPE) as a minor component and the incorporation of nano‐calcium carbonate (nano‐CaCO₃) into PP and its blends with HDPE. Three HDPEs were selected to form three blends with a viscosity ratio less than, close to, or greater than unity. Two concentrations of nano‐CaCO₃, 5 and 20 wt %, were used. The blends and nanocomposites were prepared with a twin‐screw extruder. The foaming was carried out by a batch process with supercritical carbon dioxide as a blowing agent. The online shear viscosity during compounding and the dynamic rheological properties of some samples used for foaming were measured. The cell structure of the foams was examined with scanning electron microscopy (SEM), and the morphological parameters of some foams were calculated from SEM micrographs. The rheological properties of samples were used to explain the resulting cell structure. The results showed that the blend with a viscosity ratio close to unity produced a microcellular foam with the minimum mean cell diameter (0.7 μm) and maximum cell density (1.17 × 10¹¹ cells/cm³) among the three blends. A foamed PP/nano‐CaCO₃ composite with 5 wt % nano‐CaCO₃ exhibited the largest cell density (8.4 × 10¹¹ cells/cm³). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Morphology and mechanical properties of polypropylene and poly(ethylene‐co‐methyl acrylate) blends

The morphology and mechanical properties of isotactic polypropylene (iPP) and poly(ethylene‐co‐methyl acrylate) (EMA) blends were investigated. Various EMA copolymers with different methyl acrylate (MA) comonomer content were used. iPP and EMA formed immiscible blends over the composition range studied. The crystallization and melting reflected that of the individual components and the crystallinity was not greatly affected. The size of the iPP crystals was larger in the blends than those of pure iPP, indicating that EMA may have reduced the nucleation density of the iPP; however, the growth rate of the iPP crystals was found to remain constant. The tensile elongation at break was greatly increased by the presence of EMA, although the modulus remained approximately constant until the EMA composition was greater than 20%. EMA with a 9.0% MA content provided the optimum effect on the mechanical properties of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 175–185, 2003     

Novel multimonomer‐grafted polypropylene preparation and application in polypropylene/poly(vinyl chloride) blends

A novel grafted polymer was prepared in one step through free‐radical melt grafting in a single‐screw extruder. It was shown that the addition of styrene (St) to the melt‐grafting system as a comonomer could significantly enhance the grafting degree of methyl methacrylate (MMA) onto polypropylene (PP) and reduce the degradation of the PP matrix by means of Fourier transform infrared and melt flow rate testing, respectively. Then, the potential of using multimonomer‐grafted PP, which was designated PP‐g‐(St‐co‐MMA), as the compatibilizer in PP/poly(vinyl chloride) (PVC) blends was also examined. In comparison with PP/PVC blends, the average size of the dispersed phase was greatly reduced in grafted polypropylene (gPP)/PVC blends because of the addition of the PP‐g‐(St‐co‐MMA) graft copolymer. The tensile strength of the gPP/PVC blends increased significantly, and the impact strength was unchanged from that of the pure PP/PVC blends. The results of differential scanning calorimetry and scanning electron microscopy suggested that the compatibility of the PP/PVC blends was improved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nonisothermal crystallization kinetics of polypropylene/polypropylene‐g‐polystyrene/polystyrene blends

The nonisothermal crystallization kinetics of polypropylene (PP), PP/polystyrene (PS), and PP/PP‐g‐PS/PS blends were investigated with differential scanning calorimetry at different cooling rates. The Jeziorny modified Avrami equation, Ozawa method, and Mo method were used to describe the crystallization kinetics for all of the samples. The kinetics parameters, including the half‐time of crystallization, the peak crystallization temperature, the Avrami exponent, the kinetic crystallization rate constant, the crystallization activation energy, and the F(T) and a parameters were determined. All of the results clearly indicate that the PP‐g‐PS copolymer accelerated the crystallization rate of the PP component in the PP/PP‐g‐PS/PS blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Yttria–polystyrene–polypropylene composite for fine dyeable fibers

Fine polypropylene fiber has many excellent properties, but it is difficult to dye because of the absence of dye sites in the molecular chain and high crystallinity. Fine polypropylene/hybrid polystyrene (yttria) fiber melt‐spun from blends of polypropylene and a small amount of nanohybrid polystyrene with modified yttria incorporated was prepared to improve the dyeing properties. The dyeability, orientation, degree of crystallinity, phase morphology, and mechanical properties of pure polypropylene and the blend fibers were investigated. It was found that the crystallinity and morphology of these phases in the blend systems were different. With the existence of nanohybrid polystyrene, the fine modified polypropylene filaments had practical mechanical properties, the amorphous region of the polypropylene/hybrid polystyrene (yttria) fiber increased, and the modified polypropylene fiber dyed easily and had good fastness to soaping because of the complexation of the disperse dye and yttrium in the blend system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and thermal properties of talc and calcium carbonate filled polypropylene hybrid composites

The main aim of this work was to study and compare the mechanical and thermal properties of hybrid polypropylene (PP) composites and single‐filler PP composites. With two main types of mineral fillers—calcium carbonate (CaCO₃) and talc—PP composites of different filler weight ratios (talc/CaCO₃) were compounded with a twin‐screw extruder and then injection‐molded into dumbbell specimens with an injection‐molding machine. Tensile, flexural, and impact tests were performed to determine and compare the mechanical properties of the hybrid and single‐filler PP composites. A synergistic hybridization effect was successfully achieved; the flexural strength and impact strength were highest among the hybrids when the PP/talc/CaCO₃ weight ratio was 70:15:15. The nucleating ability of the fillers and its effects on the mechanical properties were also studied with differential scanning calorimetry. Because of the influence of talc as the main nucleating agent, the hybrid fillers showed significant improvements in terms of the nucleating ability, and this contributed to the increase in or retention of the mechanical properties of the hybrid composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3327–3336, 2004     

Production of polymeric membranes made of polypropylene,poly(ethylene‐co‐vinyl acetate), and poly(vinyl alcohol)

In this study, we prepared and characterized membranes containing polypropylene, poly(ethylene‐co‐vinyl acetate) (EVA), and poly(vinyl alcohol) (PVA). The production process involved blend extrusion and calendering followed by solvent extraction by toluene and water of the EVA and PVA phases. Morphology studies involving scanning electron microscopy determined the pore size distribution at the surface and in the internal regions of the membrane. The resulting membrane properties were related to the processing variables (extension rate, process temperature, and solvent extraction methods) and blend composition. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3275–3286, 2004     

Novel intercalated nanocomposites of polypropylene,organic rectorite,and poly(ethylene octene) elastomer: Morphology and mechanical properties

The melt‐blending method was applied to prepare ternary composites of polypropylene (PP), organic rectorite (OREC), and poly(ethylene octene) elastomer (POE) with a constant content of 2 phr (parts per hundred parts of PP) OREC and 5 or 15 phr POE (PRE25 and PRE215, respectively). At the same time, OREC/PP binary composites with a 2 phr loading of OREC (PR2) and POE/PP systems with 5 or 15 phr POE (E5 and E15, respectively) were prepared to investigate synergistic effects of OREC and POE. Scanning electron microscopy was used to study the distribution of OREC and POE in the matrix, X‐ray diffraction (XRD) and transmission electron microscopy were used to investigate the intercalation performance of OREC in the composites, and polarized light microscopy (PLM) was used to observe the crystallization form and crystallite size. The mechanical properties and dynamic mechanical analysis were also measured. The PRE composites exhibited a multiphase structure, that is, a spherical texture of POE, a plate of clay, and a continuous phase of PP; a larger content of POE produced a larger size, a broader distribution of the spherical phase, and a better intercalation performance of the clay. The E systems were binary phases, that is, a spherical texture of POE and a continuous phase of PP. The crystallite size of the PRE composites was finer than that of pure PP according to XRD data, and this was confirmed by PLM. The impact strength and tensile elongation at break of the PRE composites increased dramatically in comparison with those of the PP, PR2, and corresponding E systems, and this indicated that POE and OREC had synergistic toughening and strengthening effects on PP. The storage modulus of PRE was higher than that of pure PP and lower than that of PR2. There were two glass‐transition temperatures in the PRE systems according to the curve of tan δ; they represented those of pure PP and POE, respectively, and indicated that the PRE systems were physical mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1907–1914, 2005     

Effect of maleic anhydride grafted polypropylene on the mechanical and morphological properties of chemically modified short‐pineapple‐leaf‐fiber‐reinforced polypropylene composites

With the rising cost of petroleum‐based fibers, the utilization of plant fibers in the manufacture of polymer–matrix composites is gaining importance worldwide. The scope of this study was to examine the perspective of the use of pineapple leaf fibers (PALFs) as reinforcements for polypropylene (PP). These fibers are environmentally friendly, low‐cost byproducts of pineapple cultivation and are readily available in the northeastern region of India. Here, both untreated and treated pineapple fibers were used. Maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizing agent. The polymer matrix of PP was used to prepare composite specimens with different volume fractions (5–20%) of fibers by the addition of 5% of MA‐g‐PP. These specimens were tested for their mechanical properties, and additional assessments were made via observations by scanning electron microscopy, thermogravimetric analysis, and IR spectroscopy. Increase in the impact behavior, flexural properties, and tensile moduli of the composites were noticed, and these were more appreciable in the treated fibers mixed with MA‐g‐PP. PALF in 10 vol % in PP mixed with MA‐g‐PP was the optimum and recommended composition, where the flexural properties were the maximum. The impact strength and the tensile modulus were also considerably high. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Different factors in the supercritical CO2‐assisted grafting of poly(acrylic acid) to polypropylene

The grafting of poly(acrylic acid) to polypropylene was realized with supercritical CO₂ as a substrate swelling agent and a monomer/initiator carrier. The effects of different supercritical CO₂‐assisted impregnation conditions on the substrate mass increment and grafting efficiency were studied. The original isotactic polypropylene and the grafting product were characterized through IR spectroscopy, differential scanning calorimetry, and scanning electron microscopy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4280–4285, 2006     

Thermal behavior and morphological and rheological properties of polypropylene and novel elastomeric ethylene copolymer blends

The thermal behavior including melting and crystallization behavior and morphological and rheological properties of the blends based on an isotactic polypropylene and a novel maleated elastomeric ethylene copolymer were investigated in this work. The addition of an elastomer to polypropylene (PP) was found not to change the PP crystalline structure significantly when cooled quickly from the melt. On recrystallization at a lower cooling rate, the elastomer promotes the formation of β?pseudohexagonal PP in PP‐rich blends. In elastomer‐rich compositions, heterogeneous nucleation is hindered and homogeneous nucleation takes place. These phenomena are revealed by morphology observation: that, with increasing of the elastomer content, the system undergoes PP continuous, dual‐phase continuity and PP‐dispersed morphologies. The blend viscosity at a low shear rate range increases continuously with increasing elastomer content and shows positive deviations from the additivity rule. In the terminal zone, the dynamic storage modulus of the blends shows positive deviation from the simple mixing rule and the maximum deviation lies in the composition range of dual‐phase continuity which could be caused by a large increase in the interfacial tension. The Cox–Merz rule does not hold for the blends because of the two‐phase heterogeneous structure and its variation in steady and oscillatory shear flow. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3430–3439, 2002     

Striped‐pattern deterioration and morphological analysis of injection molding comprising polypropylene/ethylene–α‐olefin rubber blends. II. Influence of heating

Unique deterioration with a striped pattern caused by thermal heating is reported for injection molding comprising polypropylene/ethylene–α‐olefin rubber blends. This stripe is due to the formation of glossy and cloudy parts in alternation approximately perpendicular to the flow direction of the molten resin. On the surface of the cloudy part, a number of micro‐objects appear. They have a dome shape about 10 μm in diameter and 2 μm height. Some experimental evidence indicates that the objects are composed of the rubber contained in the blends. On the other hand, only a few objects appear in the glossy region after heating. This is the reason that the stripe with the micro‐objects (migrating rubber to the surface) is examined in terms of a higher order structure of injection molding with laser scanning microscopy, wide‐angle X‐ray scattering, and microhardness (Martens hardness). Consequently, we have concluded that this thermally deteriorated stripe depends on periodic changes in the crystallinity along the flow direction. The evidence indicates that a snakelike flow occurs during the injection process of the molding. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Selective plasma‐induced grafting of polystyrene onto polyolefin blends

Plasma pretreatment has been used to generate reactive radicals and oxygenated groups on polymer surfaces for graft polymerization. The polymer substrates studied were composed of a polypropylene–polyethylene (PP–PE) copolymer, which was predominantly PP, and also contained blended ethylene–propylene rubber (EPR) as either about 15 or about 60 mol %. A pure PP substrate was also studied for comparison. The grafted polymer was polystyrene (PS). Raman microspectroscopic 2‐dimensional mapping was used to elucidate the role of crystallinity and EPR in the plasma treatment and graft polymerization process. It was found that the plasma pretreatment favored the EPR component of the substrate and the graft yield was related to the EPR content. Crystallinity seemed to have a much less significant effect on the grafting reaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1643–1652, 2003     

Properties of dynamically vulcanized ethylene–propylene–diene copolymer/polypropylene blends

In this study, vulcanized thermoplastic elastomers were produced through the formation of crosslinks with peroxide for different ratios of ethylene–propylene–diene copolymer to polypropylene. Mixing was performed with a twin‐screw extruder. Afterward, the yield, tensile strength, elastic modulus, elongation, Izod impact strength, hardness, melt flow index, Vicat softening point, heat deflection temperature, and density of the crosslinks were determined. The thermal transition temperatures and microstructure were determined with differential scanning calorimetry and scanning electron microscopy, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3895–3902, 2007