Nonisothermal crystallization behavior and mechanical properties of PEEK/SCF/nano-SiO2 composites

Nonisothermal crystallization of hybrid PEEK composites reinforced with short carbon fibers (SCF) and nano-SiO2 (1, 1.5 and 2 wt%) was investigated using DSC. Composites were fabricated by melt-mixing process at 400 degrees C. The Size of the nanoparticles was 13 nm. Samples were cooled from 410 degrees C to 25 degrees C with cooling rates of 10, 30, 50 and 70 degrees C min(-1). The onset, peak and end crystallization temperatures were investigated as well as absolute crystallization percentage and crystallization time. Avrami, Ozawa and Ozawa-Avrami equations were fitted to the data in order to investigate the crystallization kinetics. Mechanical behaviors of the composites were examined using nanoindentation and nanoscratching. DSC results revealed that absolute crystallization percentage increases in PEEK/SCF/1% SiO2 and PEEK/SCF/1.5%SiO2 samples compared to PEEK/SCF, however it decreases by adding more nano-SiO2. Ozawa-Avrami is proved to be the best model for describing crystallization behavior of the composites while Avrami equation was suitable for describing a part of the crystallization process. The Avrami and Ozawa-Avrami constants were calculated. Besides, adding SCFs and nano-SiO2 into PEEK results in a significant decrease in plasticity index, while increases the resistance to plastic deformation of the composite. (C) 2014 Elsevier B.V. All rights reserved.