The use of cellulose fibers derived from renewable resources as reinforcement in polymeric composites provides positive environmental benefits with respect to disposal and raw material savings. Microcrystalline cellulose is a regenerated cellulose material that is free of lignin and hemicellulose, widely used in various applications. Recently, there has been enormous interest in producing polymer nanocomposites using cellulose nanofibers as reinforcement. Moreover, the steam explosion process is an ecofriendly method to modify cellulose fibers by inducing fibrillation, allowing the production of nanofibers. Fibrillation of microcrystalline cellulose using steam explosion process as the only cellulose treatment process was not yet studied in the literature. In the present work, steam explosion process was applied to commercial microcrystalline cellulose and the obtained fibers were characterized and employed in composites with polypropylene for evaluation of the thermal, mechanical, and morphological properties in relation to the matrix. The results showed that this process promoted partial fibrillation to nanosized diameter, and an increase in crystalline degree and thermal stability of the original fiber. As for the polypropylene/cellulose composites in the absence of compatibilizer, there was an increase of thermal degradation temperature and mechanical properties measured by dynamic-mechanical analysis in comparison with pure polypropylene.

The use of cellulosic fibers from different natural sources as fillers in polymer matrices to improve their properties has been extensively studied in the last years. It is mainly due to the vast availability of natural fibers as well as their biodegradability. The purpose of this present work was to extract cellulose, silica, and cellulose-silica fillers – these last called “hybrids” – from rice husk through delignification and subsequent oxidation and, then, prepare composites with polyamide 6 and improve mainly its thermal-mechanical properties. The content of 10 wt.% of fillers was inserted in PA 6 matrix. Infrared spectroscopy pointed the main characteristic peaks of cellulose and silica of hybrids, as thermogravimetric analysis showed high thermal stability of fillers, allowing their incorporation in PA-6 matrix by extrusion method. Thermo dynamic-mechanical analysis showed, in a general overview, a significant improvement of mechanical properties of composites, as elastic modulus, compared with neat polyamide-6, mainly the one with 2.5 wt% of silica and 7.5% of cellulose. This last also showed increasing of degree of crystallinity, measured by differential scanning calorimetry, showing the extraction efficiency of fillers from rice husk as well as the potential application of composites as structural components in automotive parts.