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Understanding the sorption equilibrium of penetrants into a polymer is key to mastering the kinetics and properties of the final product. These systems are non‐ideal meaning the presence of multiple components in the continuous phase changes the solubility of individual species with respect to pure component solubilities. For this reason, measurements of the individual and total solubilities of multiple penetrants in isotactic polypropylene (iPP) and random copolymers (RCP) were performed using a pressure decay method at temperatures of 75–85°C, and total pressures of up to 29 barG. The results showed that the pure component solubilities of propylene and propane in amorphous iPP were similar, but 4 to 5 times higher than that of ethylene in the same polymer. However, in the ternary system of propylene/propane/iPP, it is seen that propylene acts as an anti‐solvent to propane, and that propane acts as an anti‐solvent to propylene, resulting in lower solubility of both penetrants than in the respective binary cases. The co‐solubility effect of propylene on ethylene and the anti‐solvent effect of ethylene on propylene were observed for the system of propylene/ethylene/RCP. [ABSTRACT FROM AUTHOR]

Catalysts and polymerization processes have evolved over the years. Such significant developments have allowed producers to broaden the range of polymer microstructure and process productivity, thereby making it possible to offer a wide range of end‐use properties at a reasonably low cost. However, these advantages in catalyst performance and reactor operation require that we understand as much as possible about reactor operation in the broadest sense. In addition to the fundamental experimental study of polymer chemistry, this means that one needs to develop complete, robust process models. The present paper provides a rapid overview of recent developments in various gas phase propylene (co)polymerization reactors in use today, concentrating on multizone gas phase polypropylene reactors: that is, multizone circulating reactor, fluidized bed reactor with internal circulation, fluidized bed reactor with external circulation, and horizontal stirred bed reactor. We then concentrate on the advances in multiscale modelling of gas phase propylene (co)polymerization reactors, from microscale kinetics at the active sites, to the mesoscale, including physical transport and thermodynamic modelling at the single‐particle level and its boundary layer, up to the macroscale reactor modelling. A systematic guideline used for the selection of appropriate thermodynamic models is proposed for gas phase olefin polymerization processes. Finally, current challenges and remaining issues related with the development of mathematical multiscale modelling are addressed. [ABSTRACT FROM AUTHOR]

Highly filled wood-substituted composites from matrices based on polymer alloys of benzoxazine resin (BA-a) and phenolic novolac resin using Hevea brasiliensis woodflour as a filler were developed. The results reveal that phenolic novolac resin can significantly reduce the curing temperature of the neat benzoxazine resin, thereby minimizing the degradation of woodflour filler during processing. The limiting oxygen indices (LOIs) of all the BP alloys were above the self-extinguishable limit i.e. >26. In addition, the LOI values were found to moderately increase whereas the rate of burning decreased as the novolac fraction in the resin mixtures increased. Furthermore, a solvent resistance experiment and thermogravimetric analysis revealed that the suitable phenolic novo-lac content should not exceed 20 wt%, to avoid the presence of unreacted phenolic in the alloy networks. The outstanding mechanical performance of the resulting wood composites is attributed to the strong interfacial interaction between the BP alloys and the woodflour filler. POLYM. ENG. SCI., 47:140-149, 2007. [C] 2007 Society of Plastics Engineers, INTRODUCTION Though human beings have a long history of utilization of wood, global environmental concerns about rapid natural forest depletion and some major drawbacks of natural wood products such as [...]

The toughness of polybenzoxazine can effectively be improved by alloying with isophorone diisocyanate (IPDI)-based urethane prepolymers (PU) or with flexible epoxy (EPO732). The experimental results, i.e., flexural testing and dynamic mechanical analysis, reveal that the toughness of the alloys of the rigid polybenzoxazine and the PU or the EPO732 systematically increases with the amount of either toughener, due to the addition of more flexible molecular segments in the polymer hybrids. The curing temperature of the benzoxazine resin (bisphenol A-aniline type [BA-a]) at about 225[degrees]C shifts to a higher value when the fraction of BA-a in either alloy decreases. Interestingly, the enhancement in the glass transition temperature ([T.sub.g]) of BA-a/PU alloys is clearly observed, i.e., [T.sub.g] of the BA-a/PU alloys are significantly higher ([T.sub.g] beyond 200[degrees]C) than those of the parent resins, i.e., 165[degrees]C for BA-a and -70[degrees]C for PU. However, this characteristic is not observed in the BA-a/EPO732 alloy systems. The enhanced [T.sub.g] of the BA-a/PU alloy at a 70/30 mass ratio is found to be 220[degrees]C, while that of BA-a/EPO732 at the same mass ratio is observed to be only 95[degrees]C, which further decreases as the content of epoxy fraction increases. Furthermore, the degradation temperature based on 5% weight loss in the thermogravimetric analyzer (TGA) thermograms of the BA-a/PU alloys is found to improve with the presence of the PU, though the opposite trend is observed in the BA-a/EPO732 systems. The char yield of both alloy systems is steadily enhanced with the increased benzoxazine content because the char yield of the polybenzoxazine is inherently higher than that of the two tougheners. Therefore, the polybenzoxazine alloys with the IPDI-based urethane prepolymer, e.g., the 70/30 BA-a/PU, are a promising system for a tough, high thermal stability polymeric network, suitable for both bulk and composite matrix applications. POLYM. ENG. SCI., 45:288-296, 2005. [c] 2005 Society of Plastics Engineers, INTRODUCTION The polybenzoxazines, a novel class of thermosetting polymers, possess some intriguing properties such as high thermal stability, easy processing ability, low water absorption, near zero shrinkage upon curing, and [...]

In this work, composite powders of natural rubber/silica (NR-SiO2) were prepared via sol-gel and spray drying method. The morphology and physical properties of resultant rubber composite powders were characterized by scanning electron microscopy with energy dispersive X-ray spectrometry, laser light scattering particle sizer and thermogravimetric analyzer. The results showed that spray-dried NR-SiO2 particles were spherical in shape with diameter of less than 10 μm, with silica on the outer layer. The particle size was found to increase gradually with the increase in NR/Si mass ratio. Marginal growth in particle size was observed with increasing feed flow rate. Increasing inlet air temperature improved the latex particle encapsulation by silica layer while maintaining the final particle size. The mechanical properties of NR-SiO2 powders-filled polylactic acid (PLA) composite increase gradually with the addition of dried particles of higher rubber content. However, the composite exhibited relatively lower or reduced tensile strength and elongation at break compared to the host PLA polymer. This could be attributed to poor filler dispersion associated with weak filler/matrix interaction effect occurring during meltcompounding process. [ABSTRACT FROM AUTHOR]