Transcrystallization of the acetylated bamboo fiber/polypropylene composite under isothermal crystallization

Abstract

The crystallization behaviors of acetylated bamboo fiber (BF)/polypropylene (PP) composites were assessed using differential scanning calorimetry (DSC) through isothermal crystallization. The transcrystalline (TC) morphologies of composites were observed through polarized optical microscopy (POM), and their surface free energies were calculated based on Hoffman‒Lauritzen theory. Isothermal DSC thermograms demonstrated that acetylated BF with higher weight percentage gains (WPGs, ~ 19%) exhibited a decreased crystallization rate of the PP matrix. POM images indicated that BF as a nucleation agent induced the TC layer on fiber–PP matrix interfaces. However, when WPG reached 19%, the TC layer was not observed on the BF surface and crystal growth was principally observed in the PP matrix bulk. Based on Hoffman‒Lauritzen theory, the folding-surface free energy (σe) and the work of chain folding (q) for acetylated BF/PP composites were estimated to be higher than those for PP composites with unmodified BF. These results indicate that BFs with different WPGs could affect the crystallization behavior of the PP matrix by inducing or hindering TC on BF–PP matrix interfaces.