Investigation of Bond Formation between Reactor Powder Grains of Ultrahigh-Molecular-Mass Polyethylene during Its Low-Temperature Compaction

摘要

The influence of the compaction time t_(com) at room temperature on the density and strength of the pellets of the UHMWPE reactor powders was studied.The pellets gain their major density and strength virtually at the moment of loading;the relative strength grows with a rise in the compaction pressure p_(com).The density and strength of pellets increases linearly with log t_(com) up t_(com)>1000 min;the slope of these curves,that is,the rate of densification and strengthening,decreases as p_(com) grpws.A mechanism was proposed for bond formation between the reaction powder grains of UHMWPE including two consecutive processes:the formation of a tight contact between grains (te formation of adhesion bonds) and the interdiffusion of macromolecular segments into adjacent grains through their interface (the formation of cohesion bonds).These processes are localized in the amorphous regions of the polymer.Changes in the crystalline regions accompanying this process have no effect on the curve of polymer melting despite the increase in its strength and density.