Nucleation Effect of Thermotropic Liquid Crystalline Polymer on the Crystallization of Poly(ε-Caprolactone)
Poly(ε-caprolactone) (PCL) has attracted much attention in recent years due to its good biodegradability and biocompatibility. As a semicrystalline polymer, the final properties of PCL strongly depend on its bulk crystallization level. However, PCL shows a lower crystallization temperature and rate than other aliphatic polyesters, which restricts its range of applications. To improve the crystallization is hence a key problem to enhance the performance of PCL materials. In this work, a thermotropic liquid crystalline polymer (TLCP) was used as a nucleating agent to improve the crystallization of PCL. The PCL/TLCP blend with the maximum TLCP content of 10 wt.% was prepared by melt mixing. The nonisothermal crystallization behaviour of the PCL matrix was studied using differential scanning calorimetry (DSC) and polarized optical microscopy (POM), and the crystallization kinetics was then further analysed by methods including the Avrami, Ozawa, Mo, Ziabicki, Lauritzen-Hoffman and Kissinger models. The results showed that the presence of the solid TLCP particles could enhance crystallization temperature of the PCL matrix evidently at very small content levels (1 wt.%). Although the mobility of the PCL chain segments decreased with increasing TLCP content, heterogeneous nucleation by TLCP particles always played a dominant role in the overall crystallization. Therefore the blends showed higher crystallization rates and ability than those of pure PCL. The kinetic analysis and the data obtained in this work could be useful to optimize the processing conditions and to improve the crystallization of PCL.