Study on Crystalline and Mechanical Properties of Thermotropic Liquid Crystal Polymer Films by Annealing
During the preparation of blow-molded liquid crystal polymer(LCP)films,the existence of rod-like macromolecular structure in LCP results in the films to be highly oriented along the extrusion direction(MD),leading to poor mechanical properties and making the film prone to tearing along the extrusion direction(TD).It is often necessary to regulate the difference of mechanical properties along the two directions by annealing.In this work,the blow-molded films of thermotropic liquid crystal polymer(TLCP)copolymerized with p-hydroxybenzoic acid(HBA)and 2-hydroxy-6-naphthoic acid(HNA)as monomers were annealed,and the effects of annealing conditions on the crystalline,mechanical and microstructural properties were investigated.The results show that increasing the annealing temperature,the crystallinity exhibits a tendency of increase then decrease,and that prolonged high-temperature annealing could significantly reduce the orientation of the molecular chains in the LCP films,which transforms them into approximate isotropy.In addition,the change of crystallinity may be related to the cross-linking reaction during annealing,proven by the rheological and gel fraction results.The mechanical properties of LCP films along MD and TD are related to the crystallinity and cross-linking during annealing.
NETL
NSTL
万方数据
