Polymer based composites are currently used in several fields including automobile, aerospace, biomedical, and domestic applications due to their high strength-to-weight ratio and other attractive properties. In the current study, silica particles are evaluated as reinforcement for three polymers namely, high impact polystyrene (HIPS), general purpose polystyrene (GPPS) and recycled low density polyethylene (rLDPE. The composites were prepared by varying the weight of silica particles in relation to the polymer matrix and then tensile, impact and thermal properties were evaluated using universal tensile testing machine, Charpy impact and differential scanning calorimeter (DSC) respectively.

The mechanical results showed that for HIPS-Silica composite, the tensile strength increased with increased silica content from 13.6 MPa for pure HIPS to 13.9 MPa at 5% silica and 14.8 GPa at 31% Silica. GPPS-Silica showed slight increase in tensile strength from 16.2 MPa for pure to 33.8 MPa at 5% silica and reduced to 21.5 MPa at 31%. The rLDPE-silica composite showed reduced tensile strength from 10.4 MPa for recycled HDPE to 10.2 MPa at 5% silica and an increase at 31% silica to 11.7 MPa. The modulus of elasticity for all the samples increased with the increasing silica content. The impact strength was found to increase from 5.6 kJ/m2 for pure PS - GPPS to 8.1 kJ/m2 at 5% silica. There was no remarkable increase in impact strength at 31% silica for PS-PPS. For HIPS composite, the impact reduced from 47 kJ/m2 for pure HIPS to 37 kJ/m2 at 5% silica and 11 kJ/m2 at 31% silica.

Thermal results of the composites at 31% silica were compared with pure respective polymers. In terms of thermal and mechanical properties, the general-purpose polystyrene had the highest heat absorption capacity and tensile strength. The modulus of elasticity was also reported highest in the general-purpose polystyrene composite. The results showed slight change in glass transition temperature and an increased heat absorption property when silica was added to respective polymers. Based on the results, natural silica (diatomite)-based composites may be used as green construction materials.

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