Efficiency of Different Chain-linking Agents in the Synthesis of Long-chain Branched Polypropylene. Molecular, Thermal and Rheological Characterization

Abstract

Long-chain branched polypropylenes were synthesized from a maleic anhydride grafted polypropylene (PPg). Different levels of branching were generated by reactive processing using four chain-linking agents: glycerol, 1,4-butanediol, 1,4-phenylenediamine, and the epoxy resin bisphenol-A diglycidyl ether. The results from Fourier transform infrared and size-exclusion chromatography confirm the grafting of the chain-linking agents onto grafted polypropylene and the generation of long-chain branches. In addition, the rheological and morphological results show that 1,4-phenylenediamine produces the largest increment of branching at significantly lower concentrations than the other chain-linking agents. Moreover, 1,4-phenylenediamine gives place to branched polypropylenes with narrower distribution of molecular structures.