Study on the effects of soluble POSS on chain disentanglement in UHMWPE polymerization

Abstract

Polyhedral oligomeric silsesquioxanes (POSS) was added in ultrahigh molecular weight polyethylene (UHMWPE) to intercalate the molecular network and produce chain disentanglement. To avoid agglomeration, the POSS/UHMWPE composites were prepared by in-situ polymerization. In particular, POSS used in this experiment is soluble in the polymerization process, so it can be dispersed in the form of nm-scale in UHMWPE. The reduced melt viscosity and the increased molecular weight between entanglement (Me) revealed that the addition of POSS can induce the disentanglement of UHMWPE and the optimal content is 0.2 wt%. The isothermal and nonisothermal crystallization behavior of nanocomposites were studied by a differential scanning calorimetry (DSC). The crystallization rate and the crystallinity of UHMWPE increased with the addition of POSS, indicating that POSS could act as a nucleating agent in UHMWPE. The annealing study was carried out by a Flash DSC and two melting peaks were observed. The data was analyzed by Arrhenius equation and the POSS/UHMWPE was found to have a lower melting activation energy than neat UHMWPE, proving the disentanglement effect of POSS on UHMWPE.