Poly- para -phenylene-copolymers (PPP) for extrusion and injection moulding Part 1 – molecular and rheological differences

Poly-para-phenylene (PPP) is at room temperature the stiffest and hardest thermoplastic polymer known. Two types of PPP (PR-120 as an extrusion and PR-250 as an injection moulding grade) are commercially available. In this paper, their thermal and rheological performance was evaluated as a function of their molecular characteristics. The lower viscosity of the PR-250 material is in agreement with its lower average molecular weight M_w, and this material exhibited a slightly higher glass transition temperature and thermal stability than material PR-120. The latter, on the other hand, possessed a much higher stiffness, as revealed by dynamic mechanical thermal analysis tests.