Crystallinity of polypropylene-silica ash composites affected by the mixing conditions - DSC studies

A mixing study of a hydrophobic polymer matrix (polypropylene) filled with a hydrophilic particulate-filler (silica from rice husk ash) was carried out using a batch mixer at a constant filler fraction of 20% (w/w). The study involves varying the mixing-time, screw speed and mixing-chamber temperature used to prepare the composites. The mechanical analysis of the samples showed that the tensile strength and modulus values were dependent on the mixing conditions. The study indicated that an increase in composite crystallinity was related to the increase in tensile modulus and the relationship was valid even when the particle size was reduced. It was found that reducing the particle size has a positive effect on the tensile modulus and strength.