The research about the preparation of submicron inorganic particles, once conducted in the past decade, is now leading to prepare polymer matrix composite (PMC) reinforced with nanofillers. The objective of present research is to study the modified effects of reinforcement dispersion of nanoparticle silica in epoxy resin on the physical properties, mechanical and thermal behaviour, and the microstructure of resultant composites. Stirrer mixing associated with manual mixing of silica sand nanoparticles (developed in our earlier research) (Ahmad and Mamat, 2012) into epoxy was followed by curing being the adopted technique to develop the subject nanocomposites. Experimental values showed that 15？wt.% addition of silica sand nanoparticles improves Young’s modulus of the composites; however, a reduction in tensile strength was also observed. Number of holes and cavities produced due to improper mixing turn out to be the main cause of effected mechanical properties. Addition of silica sand nanoparticles causes a reduction in degree of crystallinity of the nanocomposites as being observed in differential scanning calorimetry (DSC) analysis. 1. Introduction Nowadays industrial and academic research laboratories are focusing much of their efforts to develop and improve physical, mechanical, and electrical properties of polymer nanocomposites. Their interest to develop such composites is mainly because of the fact that nanoparticles present a high surface-to-volume ratio which may induct unique properties to these nanocomposites as compared to macro-scale composites [1]. Andritsch et al. [2] prepared nanocomposites filled with SiO2, Al2O3, and AIN with an average particles size from 22？nm to 10？nm and studied the nanoparticles dispersion and DC breakdown strength. They observed the highest DC breakdown strength for 0.5？wt.% for two component system. It was also noticed that the DC breakdown strength increased with 10？wt.% as compared to 2 and 5？wt.% and again decreased with 15？wt.% nano-fillers. Yasmin et al. [3] studied the dispersion of clay nanoparticles in epoxy-based composites using a three roll mill with the concentration of 1–10？wt.%. This technique was found highly efficient and environmentally friendly due to excellent dispersion of nanoparticles within a short time. Elastic modulus was improved up to 80% with 10？wt.% addition of clay nanoparticles in epoxy. Absence of any improvement in tensile strength of the nanocomposites over pure epoxy was due to the clustering of nanoparticles and/or to the occasional occurrence of nano- to microsize voids in
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