Non-isothermal Crystallization Kinetics of Kevlar Fiber-reinforced Wood Flour/hdpe Composites

Non-isothermal crystallization of neat high density polyethylene (HDPE), wood flour (WF)/HDPE composite (WPC), virgin Kevlar fiber (KF) reinforced WPC (KFWPC), and grafted Kevlar fiber (GKF) reinforced WPC (GKFWPC) was investigated by means of differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Several theoretical models were applied to describe the process of nonisothermal crystallization. The results showed that the Avrami analysis modified by Jeziorny and a method developed by Mo and coworkers successfully described the non-isothermal crystallization behavior of HDPE and composites. The Ozawa analysis, however, failed to provide an adequate description of non-isothermal crystallization. The values of crystallization peak temperature (Tp), half-time of crystallization (t1/2), and kinetic parameters KJ and F(T) showed that the crystallizability followed the order: FKWPC > GKFWPC > HDPE > WPC. The effective activation energy for non-isothermal crystallization of HDPE and composites based on both Kissinger and Friedmen methods was evaluated. WAXD indicated that the crystalline thickness perpendicular to the reflection plane (Lhkl) increased with the addition of KF. The results demonstrated that KF and GKF can act as nucleating agents and increase the crystallization rate of HDPE. Compared with GKF, KF is a more effective nucleating agent for HDPE, and wood flour cannot act as a nucleating agent for HDPE.