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Recently, for reasons both economical and environmental, recycling of waste tires based on (styrene butadiene rubber)/(natural rubber) (SBR/NR) has been widely considered. Response surface methodology (RSM) has been used to predict SBR/NR devulcanization behavior in a co-rotating twin screw extruder. In this study, variable parameters were barrel temperature, screw configuration, and content of devulcanization agent. A Box-Behnken design for the three variables, at three levels, was chosen. The sol fraction of devulcanized rubber, Δtorque (difference between maximum and minimum curing torque), and mechanical properties of revulcanizate samples were considered as the responses. The results indicated that an increase of devulcanization agent content at a certain temperature caused the sol fraction to increase. Samples including a higher sol fraction showed a lower cross-link density. Sol fraction for high shear rate screw configuration was lower than that for other screw configurations. Tensile strength of revulcanized rubber showed a decrease with a rise of devulcanization temperature. Moreover, a relationship connecting the residence time in the extruder with stagger angle and length of different kneading blocks were obtained. J. VINYL ADDIT. TECHNOL., 19:65–72, 2013. © 2013 Society of Plastics Engineers

Experimental results are presented for nanocomposite foams based on unplasticized poly(vinyl chloride)/(wood flour)/(multi-wall carbon nanotubes) (PVC/WF/MWCNTs). The nanocomposite samples were prepared in an internal mixer and foamed via a batch processing method using compression molding. Nanoparticles were functionalized by sodium hypochlorite solution, and the functionalization process was monitored by Fourier-transform infrared spectroscopy. The effects of MWCNTs (both neat and functionalized) and blowing agent concentration on the morphological properties (cell size and cell density) and mechanical properties (tensile and flexural strength) of the foam samples were studied. The results revealed that foam cell sizes decreased and cell densities increased with addition of MWCNTs. The dispersion of nanoparticles in the PVC medium was increased by functionalization, and the morphological properties of the foams containing functionalized nanoparticles were improved. Density of nanocomposite foams decreased more with functionalized MWCNTs as compared to other samples. Chemical blowing agent concentration had no significant effect on sample density. Mechanical properties of the samples were improved by using functionalized MWCNTs in comparison with those of foams without this component. J. VINYL ADDIT. TECHNOL., 18:161–167, 2012. © 2012 Society of Plastics Engineers

This paper studies the morphology and tensile properties of nanocomposite foams of blends of low-density polyethylene (LDPE) and poly(ethylene-co-vinyl acetate) (EVA). Preparations of LDPE/EVA nanocomposites were conducted in an internal mixer, and then samples were foamed via a batch foaming method. Morphology of the nanocomposite blends and nanocomposite foams was studied by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Morphological observations showed that nanoparticle dispersion in the polymeric matrix was affected by the blend ratio in a way such that EVA-rich samples had a better dispersion of nanoclay than LDPE-rich ones. In addition, the tensile properties of the nanocomposite foams were related to different variables such as blend ratio, clay content, and foam density. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers

Styrene-(maleic anhydride) copolymer (SMA) compatibilized blends of acrylonitrile-butadiene rubber (ABS) and polyamide 6 (PA6) with a variety of compositions and compatibilizer levels were prepared at various screw speeds in a corotating twin screw extruder. A Box–Behnken model for three variables, with three levels, was chosen as an experimental design, and the mechanical properties of the blends were considered as the responses. Each response was analyzed and formulated versus the considered factors by the use of response surface methodology. Impact resistance increased with increased SMA concentration and reduced screw speed. In compatibilized samples, with an increase in PA6 content, higher impact resistance was observed. Increasing PA6 content and SMA concentration, as well as decreasing screw speed, gave improvements in both tensile and flexural strengths. In each case, all of the correlations among factors were studied. Grafting of SMA was proved by detecting the graft copolymer (SMA-PA6) formed through extraction in formic acid and FTIR spectroscopy. Compared with uncompatibilized blends, compatibilized samples displayed more uniform and finer particle sizes, thereby proving the compatibilizing effect of the graft copolymer. The asymmetry trend in dispersed particle size before and after the phase inversion became more differentiated in the presence of the compatibilizer. Adding SMA lowered the phase inversion composition (based on PA6), whereas higher screw speed increased it. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers