Durability evaluation of mechanical and thermal properties of graphite-copper hybrid powder filled polypropylene composites

The sustainability of polymer composites in real time environments can be ensured by durability studies. This paper aims to evaluate the durability of mechanical and thermal properties of graphite (G) and copper (Cu) particle-filled polypropylene (PP) composites. Three types of composites, PP/G, PP/Cu, and PP/G/Cu, were prepared by melt compounding and compression molding. The compressive strength, microhardness, and thermal properties of the composites were tested after 2 and 90 days of storage under ambient conditions. The results showed a noticeable decrease in the compressive strength of the composites, reaching similar to 60-70 % compared to that of the neat PP and showed a ductile-like fracture mode. A further decrease in the strength values of similar to 90 % occurred when the composites were tested after 90 days and a brittle-like fracture mode was observed. The addition of G and Cu to PP improved its microhardness and a drastic decrease also appeared after 90 days compared to that of their counterparts tested after 2 days. DSC measurements showed that the melting temperature, T-m, decreased and crystallization temperature, T-c, increased indicating a better ability of the fillers for nucleation in PP and obstructing its crystal growth. The degree of crystallinity, X-c, of PP in the composites decreased compared to that of the neat PP and it increased when tested after 90 days compared to that tested after 2 days.