Molecular and thermo-mechanical assessment of long-chain branched polypropylene: Effect of irradiation dose, multifunctional monomer content and molecular weight

The influence of irradiation dose, trimetylolpropane trimethacrylate (TMPTMA) amount, as a three-functional monomer, and polypropylene (PP) molecular weight on the performance of irradiation technique to create long chain branched PP (LCB-PP) was investigated through molecular, rheological and thermo-mechanical characterizations. With increasing doses or amount of TMPTMA, a reduction in molar mass and an increment in long chain branches (LCBs) number as well as a change in the topology of LCBs from star to tree-like were found. PP grade with low molar mass had more branching ability and its LCBs topology was different. Irradiation declined the glass transition and melting temperature of PP, while it did not affect its crystallization temperature and its degree. Two opposing effects of molar mass reduction and LCBs formation controlled the tensile strength and toughness of irradiated PP samples.