The polymer composites were prepared from fiberglass reinforced polymer wastes obtained from cross-arm manufacturing and injection moulded after treating with latex and oven dried to reduce the itching nature of the fiberglass. The samples were size-classified as 150, 200, 250 and 300 microns. Tensile tests were later carried out on them. The mechanical properties determined include Tensile strength, Elongation at break, Hardness and Indentation. It is discovered that the tensile strength and indentation increased with increasing filler loadings while elongation and hardness decreased. The research was modelled to obtain higher filler weight percentage values that were not got in the laboratory after accurate and precise predictions were made with Matlab modelling software. The modeling was used to obtain the optimal and best results of the particle sizes