Phase In Polypropylene Matrix Research Articles

Establishment of dynamic prediction model on morphology development of polypropylene/polyamide 6 blends under in-situ fibrillation flow

In this work, the morphology development of polypropylene (PP)/polyamide 6 (PA6) blends was thoroughly investigated under in-situ fibrillation process, including shear mixing flow and uniaxial elongational flow. By establishing rheological constitutive model based on Trouton Rules, the shear and elongational rheological characteristic parameters of PP and PA6 were obtained for the establishment of the prediction model. In the shear mixing process, different screw speed was applied to evaluate the effects of the shear flow on PA6 original particle size in PP/PA6 blends. In the uniaxial stretching process, the elongational flow field characteristics were obtained through solving dynamic equation with Fourth-order Runge-Kutta method. And the evolution of PA6 droplets in obtained elongational flow field characteristics was analyzed by combining SEM results of PP/PA6 in situ fibrillar composites and theorical parameters of the deformation and breakup of the droplets (the reduced capillary number Ca*). Finally, based on force balance theory, the dynamic model of morphology development of PA6 dispersed phase in PP matrix was defined under the whole in situ fibrillation process. By comparing with experimental values, it was found that the established model was supposed to be able to predict the phase morphology development of polymer droplets well when the original particle size was smaller, and when the original particle size was larger, the coalescence between the droplets should be further considered.

Effect of compatibilizer addition on the surface nucleation of dispersed polyethylene droplets in a self-nucleated polypropylene matrix

A significant portion of the global plastics market encompasses the production of polyolefin materials and especially polypropylene (PP) and polyethylene (PE), as commodity polymers with a wide range of applications. However, the increase in the generation of unsustainable plastic waste requires a close technological look-up to address this challenge adequately. In this context, mechanical recycling is part of the strategies expected to contribute to the solution. Nevertheless, the melt blending process presents a challenge due to the immiscibility between PP and PE. Therefore, compatibilization strategies are meant to solve the problem effectively. In this paper, we employ a commercial ethylene-ran-methyl acrylate random copolymer as a compatibilizer for PP/PE blends. With the addition of the compatibilizer, it was possible to obtain a 44% reduction in PE domain size, while ductility increased by around ∼40% with respect to uncompatibilized blends. Interesting results were obtained concerning the crystallization behavior of the blends. The overall isothermal crystallization kinetics of the different blend components was studied, and a synergistic nucleation effect of the PP and the compatibilizer toward the PE phase was found. For the first time, the effect of the compatibilizer on the surface nucleation of PE in a self-nucleated PP matrix phase is reported. An enhancement in the crystallization rate of PE was found when the self-nucleation protocol was applied to the polypropylene matrix phase for neat and compatibilized blends. The nucleation efficiency was in the range of 120–124%, indicating a supernucleation behavior. The induced crystallization at the interface by the self-nucleated polypropylene is the reason for such high nucleation efficiencies. Surprisingly, a higher amount of compatibilizer decreases the overall crystallization rate of PE droplets. The compatibilizer segregates at the interface between both polymers, reducing the surface nucleation of the PE droplets on the PP matrix phase. The results presented in this paper lead the way toward improving the use of post-consumer recycled materials.

Polypropylene/thermoplastic polyurethane blends: mechanical characterizations, recyclability and sustainable development of thermoplastic materials

Nowadays, various plastic products plays an important and indispensable role in our daily life. However, plastic cannot be essentially decomposed in the nature and thus led to inevitable damage to the environment. The study aims to recycle thermoplastic materials to attain the purposes of recycling, reuse, and sustainability. Polypropylene (PP) and toughening thermoplastic polyurethane (TTPU) are melt-blended for two cycles, which a small amount of compatibilizer (i.e. polypropylene grafted maleic anhydride, PP-g-MA) is added during the process. The morphology and mechanical properties of the PP/MA/TTPU blends are then measured and investigated. SEM images show that without the compatibilizer, TTPU particles demonstrate a dispersive phase in PP matrix. The presence of compatilizer improves the incompatible situation between TTPU and PP. The impact test results have proven that the incorporation of 20 wt% of TTPU and 5 wt% of compatibilizer helps to improve the interphase problem, thereby yielding the impact strength of 63.01 J/g. The tensile strength test results show that the presence of PP compensates for the insufficient rigidity and high production cost of TTPU. The flexural strength test results show that PP with high stiffness synergizes to the softness and flexural performance of TTPU. It is expected that using the secondary recovery process obtains the added value and sustainable use of plastic products, which is helpful to the sustainable development of the earth.

A high‐barrier PP/EVOH membrane prepared through the multistage biaxial‐stretching extrusion

ABSTRACTThe polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) membranes were prepared by a novel extrusion die with an assembly of laminating‐multiplying elements (LMEs). A biaxial‐stretching occurred when polymer melts flowing through a LME. The morphology development of PP/EVOH blends and its effect on gas‐barrier property, solvent‐absorption property and mechanical properties were characterized by scanning electron microscope (SEM), polarized optical microscope (POM), gas‐permeability test, immersion experiment, differential scanning calorimetry (DSC), and tensile test. With the introduction of LME and the increasing of its number, morphology of EVOH phase in PP matrix gradually changed from zero‐dimension spherical particles to one‐dimension fibers, and then to two‐dimension sheets. As a result, the nitrogen permeability coefficient decreased nearly by two orders of magnitude and the permeability coefficient of toluene‐PP/EVOH system declined by almost four times. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45016.

Tensile Behaviour and Morphology of Polypropylene/Polycar-bonate/Polypropylene-graft-maleic Anhydride Blends

This work investigates the effect of blending polycarbonate (PC) into polypropylene (PP) matrix polymer on mechanical tensile properties and morphology. The blends, containing 5% to 35% of polycarbonate and 5% compatibilizer, were compounded using twin-screw extruder and fabricated into standard tests samples using injection molding. The compatibilizer used was polypropylene-graft-maleic anhydride (PP-g-MA). The values of tensile strengths and moduli for PP/PC/PP-g-MA blends were lower than that of pure PP. Tensile strength of pure PP was 37.74 MPa, whereas the highest tensile strength among the blends was 32.60 MPa at 70/25/5 composition. The pattern for the blends is non-linear, where the optimum amount of PC for tensile strength was 25%. Addition of PP-g-MA imparts positive effect towards the blends, shown by higher value for both tensile strength and tensile modulus compared to the noncompatibilized blend. Microscopy analysis showed PC reinforcement phase existed as particulates dispersed in PP matrix phase. PC particulates size depends on its fraction and compatibilizer content. As PC content in compatibilized blends increases, its particulate size also increases.

Mechanical properties and morphology of polypropylene/poly(acrylonitrile–butadiene–styrene) nanocomposites

Polypropylene (PP)/poly(acrylonitrile–butadiene–styrene) (ABS) blends containing montmorillonite (MMT) compatibilized with polypropylene-grafted maleic anhydride were prepared by melt extrusion using twin screw extruder followed by injection molding. Mechanical properties were evaluated through tensile, flexural, and impact testing. The microstructure and formation of nanocomposites were assessed by scanning and transmission electron microscopy and X-ray diffraction (XRD). Incorporation of polypropylene-grafted maleic anhydride and MMT into PP/ABS blend led to higher strength and stiffness but at the expense of toughness. Scanning electron micrographs revealed a fine and homogeneous dispersion of ABS phase in PP matrix. Both XRD and transmission electron microscopic analysis revealed the formation of intercalated clay silicate layer in PP/ABS nanocomposites.

THERMAL properties and morphology of Polypropylene/Polycarbonate/Polypropylene-Graft-Maleic anhydride blends

This work investigates the effect of blending polycarbonate (PC) into polypropylene (PP) matrix polymer on thermal properties and morphology. The blends, containing 5% to 35% of polycarbonate and 5% compatibilizer, were compounded using twin-screw extruder and fabricated into standard tests samples using injection or compression molding. The compatibilizer used was polypropylene-graft-maleic anhydride (PP-g-MA). Thermogravimetric analysis (TGA) showed improved thermal degradation temperature of PP/PC/PP-g-MA blends compared to pure PP. As PC content increased, the thermal degradation temperature also improved. The highest improvement of thermal degradation temperature was 23.3%, demonstrated by 60/35/5 composition. It was found that the thermal stability of PP/PC blends was improved with the addition of PP-g-MA. PP-g-MA was suspected to enhance the phase adhesion between PP and PC, thus improving thermal stability. Microscopy analysis showed PC reinforcement phase existed as particulates dispersed in PP matrix phase. PC also was in irregular shapes of fibers or flakes in certain compositions, depending on PC fraction and compatibilizer content.

Simultaneous enhancements of toughness and tensile strength for thermoplastic/elastomer blends through interfacial photocrosslinking with UV radiation

An easy procedure to introduce a photocrosslinked interface for polypropylene (PP)/maleic anhydride grafted styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer (mSEBS) thermoplastic/elastomer blends by UV radiation is reported. This procedure involves free-radical crosslinking at the interface between the mSEBS domain phase and the PP matrix phase and in the mSEBS phase domains with benzophenone (BP) as the photoinitiator and triallyl isocyanurate (TAIC) as the crosslinking agent. Compared with the absence of photocrosslinking, the structured PP/mSEBS blends with photocrosslinked interfaces confirmed by rheological measurements demonstrate simultaneous enhancements of toughness and tensile strength because of the enhanced interfacial adhesion and the more rigid mSEBS particle-like phase domains due to photocrosslinking. The tensile strength for the PP/mSEBS thermoplastic/elastomer blends with photocrosslinking increases with increasing mSEBS contents even at high mSEBS contents, and eventually approaches that for neat PP. Furthermore, the ultimate elongation at break increases with increasing crosshead speed, opposite to the general observation in that polymers tend to become brittle with increasing crosshead speed, indicating an enhanced tensile resistance for the UV radiation treated PP/mSEBS thermoplastic/elastomer blends. The procedure reported here is promising for preparing high-performance polymer blends used in high impact fields. For the purpose of comparison, PP/ethylene-propylene-diene rubber (PP/EPDM) blends were subjected to the same studies, however, the above observed simultaneous enhancements of toughness and tensile strength for the PP/mSEBS blends are completely absent for the PP/EPDM blends, simply because the UV radiation-induced interfacial crosslinking between the dispersed EPDM phase domains and the PP matrix phase does not occur.

Expanded Waste Ground Rubber Tire Powder/Polypropylene Composites: Processing-Structure Relationships

The usage of waste tire powder as dispersed phase in polypropylene matrix offers an interesting opportunity for recycling of the waste tire. In order to obtain ‘value added products’ from polypropylene (PP)/waste ground rubber tire powder (WGRT) composites, in this study, the processing of foamedPP/WGRT composites was investigated using a single-screw foam extrusion setup and chemical blowing agent. The regression models were constructed to study the relationships between the foam structure (i.e., void fraction, average cell size, and cell density) of foamed PP/WGRT composites, the processing conditions (extruder’s die temperature and screw speed), and the formulation compositions (WGRT content and blowing agent concentration) by applying a four-factor central composite design (CCD) statistical approach. The response surface plots generated using the regression models allow the rapid selection of the proper process parameters to obtain PP/WGRT composite foams with the desired density and morphology.

Miscibility enhancement of PP/PBT blends with a side‐chain liquid crystalline ionomer

AbstractSide‐chain liquid crystalline ionomer (SLCI) containing sulfonic acid groups with a polymethylhydrosiloxane main‐chain was used in the blends of polypropylene (PP) and polybutylene terephthalate (PBT) as a compatibilizer. The crystalline behavior, morphological, and mechanical properties of the blends were investigated in detail by differential scanning calorimetry (DSC), polarizing optical microscope (POM), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Revealed by the shift of Tm in DSC thermogram and the shift of the absorbed peak in FTIR spectra, specific interaction led to stronger interfacial adhesion between these phases, which resulted in much finer dispersion of the minor PBT phase in PP matrix. The SLCI containing sulfonate acid groups acted as physical crosslinking agent along the interface, which compatibilized PP/PBT blends. The mechanical property of the blends including 4 wt % SLCI contents was better than that of other SLCI contents in the blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Thermal, morphological, and mechanical characteristics of polypropylene/polybutylene terephthalate blends with a liquid crystalline polymer or ionomer

AbstractThermotropic side‐chain liquid crystalline polymer (SLCP) and corresponding side‐chain liquid crystalline ionomer (SLCI) containing sulfonate acid were used in the blends of polypropylene (PP) and polybutylene terephthalate (PBT) by melt‐mixing respectively, and thermal behavior, morphological, and mechanical properties of two series of blends were investigated by differential scanning calorimetry, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy, and tensile measurement. Compared with the immiscible phase behavior of PP/PBT/SLCP blends, SLCI containing sulfonate acid groups act as a physical compatibilizer along the interface and compatibilize PP/PBT blends. FTIR analyses identify specific intermolecular interaction between sulfonate acid groups and PBT, and then result in stronger interfacial adhesion between these phases and much finer dispersion of minor PBT phase in PP matrix. The mechanical property of the blend containing 4.0 wt % SLCI was better than that of the other blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4712–4719, 2006

Microscopic mechanism of reinforcement in single-wall carbon nanotube/polypropylene nanocomposite

We analyzed mechanical properties and structure of polypropylene fibers with different concentrations of single-wall carbon nanotubes (SWNTs) and draw down ratios (DDR). Tensile tests show a three times increase in the Young's modulus with addition of only 1 wt% SWNT, and much diminished increase of modulus with further increase in SWNT concentration. Microscopic study of the mechanism of reinforcement by SWNT included Raman spectroscopy and wide-angle X-ray diffraction (WAXD). The results show linear transfer of the applied stress from the polymer matrix to SWNT. Analysis of WAXD data demonstrates formation of a β-crystal phase in polypropylene matrix under the strain.

Barium sulfate–filled blends of polypropylene and poly(styrene‐co‐acrylonitrile)—dynamic mechanical melt state properties and interlayer effects

AbstractDifferent microstructures were obtained as a result of the chemical character of the polymer phases in barium sulfate–filled blends of polypropylene (PP) and poly(styrene‐co‐acrylonitrile) (SAN). The microstructure was controlled with the aid of low molecular mass maleic anhydride–grafted polypropylene (PP‐g‐MAH), which seems to form an interlayer around the filler particles resulting in controlling of the polymer phase in which the filler is occluded. The variation of the properties as a function of the concentration of PP‐g‐MAH with different amounts of grafted maleic anhydride and the average filler size was found to be due to a change of the microstructure. A low molecular weight PP‐g‐MAH interlayer around the filler particles occluded in the PP phase, dilution of the filler when occluded in the PP matrix phase of low viscosity as compared with SAN and filler network formation were found to be of importance for the dynamic mechanical properties. A theoretical model, the interlayer model, was used to simulate the dynamic mechanical properties of the filled blends.