Long-chain branched polypropylene obtained using an epoxy resin as crosslinking agent

A reaction between a linear polypropylene functionalized with maleic anhydride (PPg) and epoxy resin (bisphenol A diglycidyl ether) was carried out on the molten state to generate long-chain branches (LCB) in the molecular structure of the PPg. Concentrations of epoxy resin (ER) of up to 3.15 wt% were employed to obtain different levels of branching. FTIR spectroscopy analysis indicates that during the reaction, anhydride groups in PPg are consumed and new ester groups are formed. The presence of branches was verified using multiple-detection size-exclusion chromatography and rheology. The degree of long-chain branching induced in PPg augments with increasing concentration of ER. Furthermore, the materials modified with higher content of ER display gel-like behavior. The long-chain branched polymers also display thermo-rheological complexity. Thermal characterization studies show that LCBs have a nucleating effect during crystallization and cause the augment of the crystallization activation energy of PPg.