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The foaming behavior of high‐melt strength polypropylene (HMS‐PP) and HMS‐PP/Cloisite 20A nanocomposites (PPNC) was studied in a batch process. PPNCs with 2, 4, 8, and 10 wt% clay were prepared in a twin screw extruder. The morphology of the nanocomposites was studied using XRD and TEM. Subsequently, foaming experiments were conducted using supercritical CO2 as the blowing agent in a batch process, and foams with cell sizes varying from the sub micrometer to the micro meter range were prepared. The effect of variation in saturation pressure and temperature, foaming temperature, foaming time, and quench temperature was determined experimentally. Dynamic rheological measurements were conducted to relate the influence of nanocomposites morphology with foam cell growth and nucleation. Extensional rheological measurements were also conducted to detect the presence of strain hardening effect at the foaming temperatures used in the experiment. It was found that the nucleation efficiency of clay reduces with increase in clay loading. Also, the optimum amount of filler for generation of fine celled foams was found to be around the percolation threshold of the polymer. The extended strain hardening effect shown by the polymer in presence of clay plays an important role in stabilizing foam cell sizes. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

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Born more out of necessity, the "awareness-attitude" of our society has caused the channeling of technological developments toward immediate economic and ecological benefits. The polymer industry has a newfound interest in fillers from industrial by-products and other waste materials having potential "recyclability." This new class of fillers includes fillers from natural sources (e.g., natural fibers), industrial by-products (e.g., saw dust, rice husks), and a recent entry in the form of rice husk ash-an industrial waste material-obtained by burning rice husks. Their recyclability and utilization has become a major driving factor in their acceptance and employability, as well as low cost and abundant availability. However, their performance in composites and processing requirements has hindered their applicability within the current economic framework. The present article reviews the performance of rice husk ash, or silica ash, in polymeric composites. Silica ash, composed mainly of silica, is obtained after burning rice husks and is a major industrial waste material in rice growing countries. Optimism surrounds the application of silica ash as a potential filler in a variety of polymeric composites, however, its performance has been limited by its inherent characteristics. This paper emphasizes the need for better characterization of silica ash to obtain an in-depth understanding of its behaviour with the view to identifying suitable modifications to improve its performance as a filler. It is emphasized that poor understanding of silica ash as a

This work focuses on development and optimization of polylactide (PLA) and nanographite platelets (NGP) based composites to display possible superior mechanical and improved thermal stability. Melt blending and dry mixing methods of fabrication were employed at temperature of 180°C. Different Loading fractions of NGP were incorporated into polymer matrix. Morphological evaluation techniques such as XRD and TEM were applied to determine the degree of dispersion of NGPs into PLA matrix. Mechanical properties were evaluated and correlated to structural morphologies of PLA/NGP composites. Thermal properties of composites were studied to examine possible changes in Tg, Tc, Tm, and percentage crystallinity of these composites. The effect of mixing was also explored through double extrusion of some samples. It was concluded that composites containing 3 wt% NGP showed optimum mechanical performance without any significant changes in the thermal characteristics. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers

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Rice hulls, a byproduct of the rice industry, contain 60 -90% silica and are unique within nature. The annual worldwide output of rice-hull-derived silica is more than 3.2 million tons, which poses environmental concerns because of disposal issues. Burning rice hulls, as a preparative step for energy production, is a useful solution to the growing environmental concern, a desirable outcome would be the economic use of the resulting silica-rich hull ash. The economical usefulness of this silica ash in the filler market has been undermined by its limited dispersion abilities and poor interaction capability with polymers. In this study, some of the reasons for the poor performance of silica ash as a reinforcing filler in various polymeric composites were linked to its inherent characteristics: factors such as its impurity, irregular topography, porosity, and chemical and thermodynamic nature arising from its surface polarity that negatively influence the filler-matrix interactions. The silica ash obtained from a novel combustion process had about 6% (w/w) impurity, of which around 3% was volatile. We also propose that the silanation efficiency of silica ash is lower compared to other commercial silicas because of its porosity, which could hide a fraction of the silane used. Also, processing changed the particle size distribution, and this could have affected the agglomerating tendencies and seriously marked the reinforcing capabilities of the silica ash. The estimation of the surface silanol groups of the rice hull ash by thermogravimetric studies indicated that the surface silanol density was about 16/nm 2 . On a comparative scale, this value is comparable to the silanol density on precipitated silica, but a thermodynamic study of silica ash surface revealed a high surface free energy that contributed to its high aggregation tendencies and poor distribution and dispersion abilities.