Preparation of isotactic polypropylene/polystyrene blends by diffusion and subsequent polymerization of styrene in isotactic polypropylene pellets

Isotactic polypropylene (iPP) pellets were used to prepare isotactic polypropylene/polystyrene (iPP/PS) blends by diffusion and subsequent polymerization of styrene in water medium, with initiator benzoyl peroxide (BPO) added after diffusion of styrene. Two methods, differencing in whether the excess monomer was removed after diffusion, were used and parameters influencing PS contents were investigated. Diffusion kinetic study showed that the diffusion coefficient at 90 °C is 2.8 times that at 80 °C due to the α relaxation of iPP segments. Investigation on the distribution state of styrene in the mixture before diffusion revealed that most styrene adsorbed on the surface of iPP pellets, and thus the diffusion behavior of styrene into iPP pellets in water medium is similar to that in bulk styrene. Phase morphology of a typical iPP/PS blend showed an average particle size of about 90 nm in the inner part of the iPP pellets. The diametrical distributions of PS showed that styrene can diffuse up to the center of the pellets at 90 °C. It is important to note that the depth of styrene is limited when the initiator BPO is added along with styrene, providing a good explanation for the previously reported ineffective solid-state modification of melt-extruded iPP pellets.     

Dynamic mechanical properties of polystyrene–aluminum nitride composite

A composite of aluminum nitride (AlN) particles dispersed around polystyrene matrix particles was synthesized in this study. The purpose of using this microstructure is to improve the thermal properties of a polymer at a low filler content with a minimal increase in the dielectric constant of the polymer composite to meet the material requirements for electronic packaging. The dynamic mechanical properties of this type of polystyrene–AlN composite were investigated here. The experimental results indicate that the dynamic mechanical property of the polystyrene–AlN composite is a function of the polystyrene particle size, AlN filler concentration, and temperature under this dispersion state. The addition of an AlN concentration into polystyrene increases both the storage modulus and the α‐transition temperature. The smaller polystyrene particle size gives a higher storage modulus and damping peak. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1348–1353, 2000     

Kinetics-controlled compatibilization of immiscible polypropylene/polystyrene blends using nano-SiO2 particles

Rigid inorganic filler has been long time used as a reinforcement agent for polymer materials. Recently, more work is focused on the possibility that using filler as a compatibilizer for immiscible polymer blends. In this article, we reported our efforts on the change of phase morphology and properties of immiscible polypropylene(PP)/polystyrene(PS) blends compatibilized with nano-SiO₂ particles. The effects of filler content and mixing time on the phase morphology, crystallization behavior, rheology, and mechanical properties were investigated by SEM, DSC, ARES and mechanical test. A drastic reduction of PS phase size and a very homogeneous size distribution were observed by introducing nano-SiO₂ particles in the blends at short mixing time. However, at longer mixing time an increase of PS size was seen again, indicating a kinetics-controlled compatibilization. This conclusion was further supported by the unchanged glass transition temperature of PS and by increased viscosity in the blends after adding nano-SiO₂ particles. The compatibilization mechanism of nano-SiO₂ particles in PP/PS blends was proposed based on kinetics consideration.     

Preparation of polyamide 6/polystyrene quasi‐nanoblends by diffusion and subsequent polymerization of styrene in water‐sorbed polyamide 6 pellets

Polyamide 6 (PA6)/polystyrene (PS) blends with an average particle size of 103 nm were prepared by diffusion and subsequent polymerization of styrene in water‐sorbed PA6 pellets. The pretreatment of PA6 pellets in hot water is prerequisite for successful styrene diffusion. The diffusion process involves replacement of free water in the pellets by styrene, and should be carried out in neat styrene medium to provide concentration gradient between inside and outside of the pellets. The polymerization step was carried out in water medium with benzoic peroxide as the initiator. The diametrical distribution of PS in the blend pellets was investigated by Micro‐FTIR, and molecular weight of PS was measured by GPC. DSC measurements showed that the diffusion and polymerization of styrene occur in the amorphous regions of PA6 where the pre‐sorbed water locates. PA6/PS quasi‐nanoblends reported in this work cannot be obtained by conventional methods. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44554.     

EFFECTS OF GLASS MICROFILLERS ON THE WATER-TRANSPORT BEHAVIOR OF POLYURETHANE COMPOSITES

Glass microspheres with unique composition and diameter, and modified by different surface treatments, were blended with polyurethane (PU) in various proportions to improve the liquid transport properties of the PU composites. Transport properties such as diffusion, permeability, and sorption coefficient were measured on various filler-filled PU composites at three different temperatures. These temperature-dependent parameters were used to provide a quantitative way to examine the effects of filler loading and the surface properties on the improvement of the water transport properties of PU composites. Results show that due to trapping at interfacial boundaries between filler and polymer, a high water affinity and large space for water activity is expected inside all the filler-filled composites. As a result, lower water diffusion (or high water resistivity) was found among all the filler-filled composites compared to that of filler-free composites. Besides, the more filler present in the composite, the longer the paths of the water molecules within the composites as the water penetration proceeds. Thus, lower diffusion coefficient values were observed for composites with large amounts of filler addition.     

Production of filled hydrogels by mechanochemically induced polymerization

Silica nanoparticles functionalized with polyvinylpyrrolidone (PVP) were obtained by the grinding/mechanical activation of quartz or nonfunctionalized silica nanoparticles in a stirred media mill in the presence of 1‐vinyl‐2‐pyrrolidone, as proven by Fourier transform infrared spectroscopy. The polymer layer thickness formed on the silica nanoparticles after 8 h of mechanical activation in the absence of polymerization initiators amounted to about 10 nm, as derived from shear rheology. The silica nanoparticles functionalized with the hydrophilic PVP by mechanochemical polymerization reaction were used as fillers for hydrogels based on poly(hydroxyethyl methacrylate) (polyHEMA). The water absorption, release properties, and mechanical properties of the polyHEMA–silica composites were measured as functions of the filler content and particle size of the filler. PolyHEMA samples containing 20 wt % of the functionalized silica particles exhibited a higher maximum water absorption than the unfilled polymer; this showed that the hydrophilic interface between the filler and the matrix improved the water absorption. The release of methylene blue from the polyHEMA–silica composites was governed by diffusion and was almost unaffected by the silica particles. The values for the storage modulus and loss modulus of the polyHEMA–silica composites increased with growing filler content. For constant filler content, the storage modulus increased with decreasing particle diameter of the filler; this showed that the reinforcing effect increased with the interface between the filler particles and the matrix polymer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Evaluation of properties of unsaturated polyester/acetylated hydroxypropyl guar gum composites

Guar gum is a naturally occurring galactomannan, which is extremely hydrophilic in nature. Hydroxypropyl guar gum (HPG) was subjected to acetylation using acetic anhydride and pyridine. The effect of the reduction in the hydrophilic nature of the polymer on its filler properties was studied by using the derivatized guar gum as filler in an unsaturated polyester composite. The effect of degree of substitution and the concentration of filler on the rheological, chemical, and mechanical properties of the composites were studied. Results indicated that an increase in the acetate content in the HPG resulted in an increased polymer–filler interaction. However, the composites resulting from these derivatized HPGs showed reduced mechanical properties. This decrease in the mechanical properties were attributed to the decrease in the hydrogen bonding in the filler particles, thus reducing the cohesiveness and strength of the filler particles themselves. Thus, polysaccharides can be used as fillers but chemically modifying them results in a change in the basic nature of the filler itself and is not just restricted to surface modification as is the case of inorganic fillers and fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheological behavior of low molecular weight polystyrene composites containing monodisperse crosslinked polystyrene beads

Steady shear viscosities and dynamic moduli of polymer composites, consisting of crosslinked polystyrene beads and low molecular weight polystyrene matrix, were measured in a cone-and-plate rheometer at different temperatures. Viscosities and dynamic moduli were found to be very sensitive to filler loading and measurement temperature. Steady shear viscosities of 30% and 40% loaded low molecular polystyrene composites showed a power-law behavior over the entire range of shear rates. Storage and loss moduli were initially linear with frequency on double logarithmic plots, with limiting slopes of 0.3 and 0.1. At high concentration of filler particles, they showed a flat plateau at low frequencies, indicating that these systems exhibit a yield behavior. A 20% PS composite loaded with beads of high crosslink densities resulted in poor dispersion of beads as a result of poor dispersion of particles. PS beads 1.16 μm in diameter showed a higher viscosity. It is due to the apparent increase in loading resulting from broken particles. At low measurement temperature, filler effects were suppressed by high viscosity matrix and showed a similar rheological behavior to high molecular weight by PS matrix. We suggest that rheological behavior reflects the state of dispersion of beads in the matrix.     

Water sorption and diffusion in starch/polyolefin blends

The kinetics of water sorption by starch filled polyolefins has been investigated using blends of commercial starch masterbatch with low density polyethylene (LDPE), high density PE (HDPE), and copolymers of ethylene with methyl acrylate (EMA), ethyl (EEA), AND n-butyl acrylate (EBA). Transient state diffusion coefficients (D) of water in the blends were determined using Fickian analysis of the initial stages of the sorption isotherms. Measured D values were several orders of magnitude lower than values reported for either pure starch of LIDPE by various investigators. Resin effects on D were on the order D_HDPE < D_LDPE ? D_EBA < D_EEA < D_EMA. The resin effects diminished as the starch content increased. The lower magnitude of D in the blends relative to pure LDPE was attributed to the sorption of water by the dry starch particles, in a manner similar to dual-mode sorption in glassy polymers. Copolymer effects were consistent with reduction in crystallinity caused by the comonomers. The dependence of the diffusion coefficient on starch content was not described by mixing models of heterogeneous systems of percolation theory.     

Synthesis and properties of amphiphilic nonspherical SPS/PS composite particles by multi-step seeded swelling polymerization

Amphiphilic nonspherical particles have asymmetric surface physical and chemical properties. Such a unique structure makes them suitable for applications in many areas, such as chemical and biological sensors, colloidal surfactants, self-assembly, building blocks of complex superstructures, and materials engineering. In this study, amphiphilic sulfonated polystyrene/polystyrene (SPS/PS) composite particles with controllable morphologies are synthesized by combining modified treatment and multistage seeded swelling polymerization. Core-shell SPS particles were first obtained by modifying cross-linked PS particles with concentrated sulfuric acid, and the surface of SPS particles was a hydrophilic sulfonated polystyrene layer. With further twice seeded swelling polymerization, new hydrophobic PS oil phase sprouted on the strong hydrophilic surface even without any surfactant assistance in aqueous media. The morphologies of these SPS/PS composite particles could be adjusted by changing the crosslinking density of the seed microspheres, the sulfonation temperature and the swelling ratio of monomer/seed. These polymer composite particles can be used as solid surfactants.     

Water vapor sorption and diffusion in wheat straw particles and their impact on the mass transfer properties of biocomposites

This work intends to decipher the role of hydrophilic fillers, wheat straw fibers (WSF), on the water vapor transfer properties (sorption and diffusion) of biocomposites based on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), (PHBV) as matrix. Transfer in biocomposites, measured using dynamical vapor sorption measurement, is correlated to the transfer properties of each individual constituent and to the specific structural arrangements induced by the presence of particles inside the matrix. Increasing amounts of WSF particles in the PHBV matrix lead to an increase of the water vapor sorption (WVS) of the resulting composites. This is attributed to the high sorption of hydrophilic WSF as compared to that of the neat PHBV matrix. Water vapor diffusion in composites (around 0.13 × 10^?11 m² s^?1 at 20°C whatever the filler content) is always lower than in the neat matrix (0.26 × 10^?11 m² s^?1) although wheat straw displays high diffusivity values (1.84 × 10^?11 m² s^?1). Such unexpected behavior is related to (1) changes of structure and properties of the WSF particle once embedded in the PHBV matrix, (2) changes in the polymer matrix structure and properties in contact with fibers, and also (3) to the representativeness of the filler diffusivity, which is difficult to appraise. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43329.     

Influence of the incorporation of fine calcium carbonate particles on the impact strength of polypropylene/polystyrene‐block‐poly(ethylene butene)‐block‐polystyrene blends

The Izod impact strength of two kinds of ternary composites was investigated. One consisted of polypropylene (PP), the triblock copolymer polystyrene‐block‐poly(ethylene butene)‐block‐polystyrene (SEBS), and calcium carbonate (CaCO₃) particles, and the other consisted of PP, carboxylated SEBS (C‐SEBS), and CaCO₃ particles. The mean size of the CaCO₃ particles was about 160 nm. According to scanning electron microscopy observations, the composite with SEBS showed a morphology in which SEBS domains and CaCO₃ particles were independently dispersed in the PP matrix. On the other hand, the composite with C‐SEBS showed a morphology in which CaCO₃ particles were encapsulated by C‐SEBS; that is, a core–shell structure was formed. The Izod impact strength of the composite with SEBS was higher than that of the composite with C‐SEBS and the PP/SEBS and PP/C‐SEBS binary blends. According to observations of the fractured surface, the stress‐whitened area was larger in the composite with SEBS than in the composite with C‐SEBS and the PP/SEBS and PP/C‐SEBS binary blends. The toughening mechanism of the composite, using nanometer‐sized CaCO₃ particles in combination with SEBS, was examined. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Control of the Surface Properties in Polymer Blends

We report on the preparation of amphiphilic diblock copolymers containing a hydrophilic segment, poly(acrylic acid)(PAA), and a polystyrene hydrophobic part. We analysed, by means of contact-angle measurements, how the hydrophilic segments usually bury themselves under the hydrophobic when exposed to air to reduce the surface free energy of the system. In contrast, in contact with water, the hydrophilic blocks have a tendency to segregate to the interface. We first describe the parameters that control the surface reconstruction when the environmental conditions are inversed from dry air to water vapour. Then, annealing time, temperature, composition and size of the diblock copolymers, and size of the matrix that influenced the surface migration process are the main parameters also considered. Finally, the density of the carboxylic functions placed at the surface was determined using the methylene blue method.     

Flow through diffusion cell method: A novel approach to study in vitro enzymatic degradation of a starch‐based ternary semi‐interpenetrating network for gastrointestinal drug delivery

A ter‐polymeric semi‐IPN has been synthesized by aqueous polymerization of methacrylamide in the presence of polyethylene glycol (PEG) and natural polysaccharides starch, and its enzymatic degradation has been studied in the phosphate buffer medium of pH 6.8 at the physiological temperature 37°C. With the increase in content of enzyme in the external solution and starch in the hydrogel, the degradation is enhanced while the extent of degradation is lowered with the increase in the amount of PEG in the hydrogel. The initial water content also affects the degradability of the polymer matrix. The degradation follows Michaelis–Menten kinetics and K_M was found to be 3.92 × 10^?5 mol dm^?3. The hydrogel exhibits different degradation behavior when studied by “traditional degradation method” (TDM) and “flow through diffusion cell” (FTDC) method. The degradability is suppressed in FTDC method because of the absorption of amylase molecules onto filler particles. Finally the nature and size of the filler particles also affects the degradation behavior of hydrogels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2975–2984, 2006     

Filler and mobility of rubber matrix molecules

Filler surfaces in elastomers influence mobility of rubber matrix molecules. Mobility of rubber matrix molecules then determines elastomer properties and behaviour of rubber products in applications. Effect of filler in elastomer–filler system is usually characterized by different properties: Modulus seem to depend mainly on filler cluster size and filler network behaviour but effect of mobility of rubber matrix molecules is also evident. Bound rubber characterize fraction of rubber immobilized on filler particle surfaces, however, can be obtained only for uncured rubber–filler compounds. As it is shown in this paper, the permeability coefficient of permanent gas in rubber–filler system could characterize mobility of rubber matrix molecules around the filler particles and the activation energy of its permeation could characterize strength of physical bonds between the rubber matrix molecules and surface of filler particles.     

Mechanical properties and water vapor permeability of starch/montmorillonite nanocomposites

Results of an investigation into an unmodified‐montmorillonite (MMT)‐filled nanocomposite based on plasticized starch are reported. Data on the influence of MMT content on the tensile mechanical properties of the material are presented. Particular attention is given to the water vapor permeability of the nanocomposite. It is found that the resistance to water permeation of plasticized starch can be improved considerably by introducing a rather small amount of the filler into it. Data on the influence of MMT content on the coefficients of moisture diffusion, solubility, and permeability are reported. Also, a simple method for determining the effect of irregularly oriented platelike filler particles on the permeability of the composite material is suggested. The calculation results are compared with experimental data. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Biodegradable polymer blends of poly(L‐lactic acid) and gelatinized starch

Gelatinized starches were prepared with various content of glycerol and were investigated in terms of the effect of the glycerol addition on characteristics of starch and its blends. Poly (L‐lactic acid) (PLA) with various ratios of linear/star shaped PLA and starch gelatinized with various ratios of water/glycerol were melt‐blended by using twin screw mixer. The blends were characterized by DSC thermal analysis, tensile test and morphological analysis. Gelatinization of starch was found to lead to destruction or diminution of hydrogen bonding in granules and a decrease of crystallinity of starch. DSC data showed that starch played a role as a nucleating agent and glycerol as plasticizer contributed to an improvement in crystallinity in PLA blends. When the content of starch increased, the size of spherulites in PLA blends was smaller and less regular. In the case of PLA/pure starch blends, the voids appeared, which were formed by the separation of starch particles from the matrix. But for PLA/gelainized starch blends, these voids were not observed. In the case of blends with linear PLA and starch gelatinized with water/glycerol ratio of 100/40, the greatest superiority of mechanical properties was shown and the toughness was improved compared with PLA/pure starch blends.     

Dispersion of a novel phenolic rigid organic filler in isotactic polypropylene matrix by solution-mixing and melt-mixing

A novel phenolic rigid organic filler (named KD) with a high melting point was dispersed in an isotactic polypropylene (iPP) matrix by solution-mixing and/or melt-mixing. A series of KD/iPP blends was prepared with or without addition of maleic anhydride-grafted polypropylene (MAPP) as a compatibilizer. Influences of MAPP and mixing methods on the filler dispersion were studied using polaried optical microscope (POM), scanning electron microscope (SEM) and tensile test. The filler particles are always inclined to form large irregular aggregates in the iPP matrix due to their significant differences in polarity and solubility in solvent. However, an iPP/MAPP/KD (PMK) blend containing filler particles with a quasi-spherical shape (~97.8 nm in diameter) and narrow particle size distribution (polydispersity index= 1.076) was successfully prepared by incorporating MAPP to reduce the interfacial tension and surface free energy between the dispersion phase and the continuous phase, and adopting a spray-drying method after solution-mixing to suppress the increase of the size of the dispersed phase during the removal of solvent.     

Preparation and characterization of starch‐based composite films reinforced by corn and wheat hulls

Biodegradable films, with starch as a matrix, were developed and reinforced with wheat and corn hulls. The effect of the particle size of the filler on the microstructure and mechanical and barrier properties of starch‐based films was investigated. We observed that the addition of hulls enhanced the modulus, tensile strength, and impact strength of the starch matrix at the expense of its elongation. The water‐vapor transmission rate results show that corn starch was more efficient in reducing the water‐vapor permeability than wheat hulls. Scanning electron microscopy observations indicated that the compatibility of both fillers with the matrix was quite good; this was expected because all of the components used in this study were hydrophilic and exhibited polar behavior. Optical microscopy and X‐ray diffraction observations indicated that the processing conditions did not affect the crystalline and geometric structures of the hulls. Because all of the components used in this study were from food resources, the films could also be used for edible packaging. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45159.     

EP/氧化石墨烯–硬脂酸丁酯微胶囊复合材料

采用种子微悬浮聚合法制备了聚苯乙烯/氧化石墨烯复合囊壁包覆硬脂酸丁酯微胶囊润滑材料(MGO–Micro LMs),以MGO–Micro LMs为润滑填料,环氧树脂(EP)为基体材料,采用浇注成型工艺制备了EP/MGO–Micro LMs复合材料。采用滑动摩擦磨损试验仪评价了MGO–Micro LMs对EP基体材料摩擦学性能的影响;采用扫描电子显微镜对磨损面的微观形貌进行表征,并探究了其磨损机理。结果表明,MGO–Micro LMs能够显著地降低EP的摩擦系数和磨损量,当MGO–Micro LMs质量分数为20%时,EP/MGO–Micro LMs复合材料的摩擦系数为0.138 44,磨损量减少了约42.3%,磨损机理主要为磨粒磨损。