Abstract
Polyethylene (PE) and polypropylene (PP) were reacted with benzoyl peroxide (BPO) and 2,2,6,6โtetramethylโ1โpiperidinyloxy (TEMPO) to prepare PEโTEMPO and PPโTEMPO macroinitiators, respectively. Molecular weight of PP decreased, whereas that of PE increased during the reaction with the BPO/TEMPO system. Polystyrene (PS) branches were grafted to PE and PP backbone chains as a result of bulk polymerization of styrene with the PEโTEMPO and PPโTEMPO macroinitiators. A significant amount of PS homopolymer was produced as a byproduct. Weight of the resulting PEโgโPS and PPโgโPS increased with the polymerization time up to 20 h and then leveled off. Melting point of PE and PP domains in PEโgโPS and PPโgโPS, respectively, lowered as the content of PS in the copolymers increased. However, glass transition of the copolymers was almost identical with that of PS homopolymer, indicating that the constituents in the copolymers were all phaseโseparated from each other. In scanning electron microscopy of the incompatible PE/PS, PP/PS, and PE/PP/PS compounded with PEโgโPS and PPโgโPS, any clear indication of enhanced adhesion between the phases was not observed. However, phase domains in the blends were, nevertheless, reduced significantly to raise mechanical properties such as maximum stress and elongation at break by 20โ75%. ยฉ 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1103โ1111, 2002