Disentangled State in Polymer Melts; a Route to Ultimate Physical and Mechanical Properties

Abstract The role of entanglements in obtaining a homogeneous product of ultra high molecular weight polyethylene (UHMW‐PE) has been explored. Studies performed in this report show that a disentangled state before melting is a prerequisite to obtain homogeneous products of an intractable polymer like UHMW‐PE. The disentangled state is obtained directly from the reactor by controlling the polymerisation conditions or in the solid state when there is enhanced chain mobility along the c‐axis of a unit cell. The disentangled state is maintained in the melt over a period of time, invoking implications in polymer rheology. This approach is applicable to polymers in general. The homogeneous fully sintered UHMW‐PE, obtained for the first time, shows a considerable decrease in oxygen permeability, and increase in toughness and fatigue resistance. Such homogeneous products of UHMW‐PE are of beneficial in highly demanding applications, especially in knee‐prosthesis, where the polymer is used as an inlay between the human bone and a metal or ceramic part, which slides against the polyethylene component during normal gait. Phase diagram for the extended chain crystals. magnified image Phase diagram for the extended chain crystals.