The relation between spinnability of thermotropic liquid-crystalline polymers and their submicrometre reinforcing function in polymer blends

Six thermotropic liquid-crystalline polymers (TLCPs) were spun on a CSI 194 Mini-Max extruder in their optimized spinning-temperature ranges. Based on the diameter and the diameter distribution of the resultant fibres, these TLCPs were classified into two groups with good and poor spinnability, respectively. The viscosity ratio of TLCP to matrix resin, eta(d)/eta(m), in the optimized spinning-temperature range was used as a parameter for controlling TLCP fibrillation in the resin matrix. For a TLCP having good spinnability, its morphology in different resins was observed and correlated with the viscosity ratio in the range of 10(-2) to 10. With decreasing eta(d)/eta(m) from 16 to 0.05, the dispersed TLCP phase changes from spheres through ellipsoids and short rods to fibrils. Under the same condition, i.e. in the eta(d)/eta(m), range of 0.01 to 0.1, TLCPs with good spinnability generate fibrils in injection-moulded samples, while poor spinnability ellipsoids and rods only are generated. The results of image analysis show that two TLCPs with good spinnability generate fibrils of smaller diameters, narrower diameter distributions and larger intrinsic aspect ratios. It is shown that there is a correlation between the TLCP spinnability in air and TLCP fibrillation in the resin melt. This could be taken as a prerequisite for the achievement of submicrometre reinforcing with LCP fibrils.