PROCESSING OF MELT PROCESSABLE LIQUID CRYSTAL POLYMER BY CONTROL OF THERMAL HISTORY

摘要

A process for the extrusion of melt processable liquid crystal polymer which provides improved processability characteristics is provided. The process comprises the steps of subjecting the liquid crystal polymer to an elevated temperature between the DSC transition temperature and the degradation temperature of the polymer; cooling the liquid crystal polymer to a processing temperature which is between the DSC transition temperature and the elevated temperature and at which the liquid crystal polymer is less subject to degradation than at the elevated temperature; and extruding the liquid crystal polymer into the form of a shaped article having mechanical properties which are improved over those of articles formed from liquid crystal polymer which has not been subjected to the elevated temperature. Preferably, the liquid crystal polymer exhibits at the elevated temperature a reduction by at least a factor of 5 in the melt viscosity of the liquid crystal polymer, as compared to the melt viscosity at the DSC transition temperature, without significant degradation of the liquid crystal polymer. The reduction in melt viscosity is substantially retained by the liquid crystal polymer at the processing temperature, and the liquid crystal polymer is extruded into the form of a shaped article while the reduction in melt viscosity is thus retained. By employing the process of the present invention, melt processable liquid crystal polymers can be conveniently processed at temperatures near the DSC transition temperature rather than at the higher temperatures commonly encountered in the prior art at which degradation is more likely to occur.