Non-isothermal crystallization of UHMWPE filled during polymerization with inorganic fillers

Abstract

The non-isothermal crystallization of UHMWPE, filled with different inorganic fillers during the polymerization on the catalyst system TiCl₄/(C₂H₅)₂AlCl/(C₆H₅)₂Mg has been studied by DSC and polarization microscopy. The melting conditions of UHMWPE have been established before the crystallization experiments. It is shown that the fillers act as nucleating agents only when the crystallization is carried out from a melt, obtained at temperature above the flow temperature of UHMWPE, and at slow cooling rate. It was established that the efficiency of nucleation passes through maximum at 50 wt.% of the filler. It is assumed that this is due to the reduction of the heterogeneous sites, because of the aggregation of the filler with high concentration. The non-isothermal crystallization kinetics is studied by Harnisch and Muschik method. The Avrami exponents do not change in the presence of a filler with concentration up to 90 wt.%.