Study On Crystalline Morphology Of PET Fibers Filled IPP Composites By Means Of Polarized Optical Microscope

As the bridge between reinforcement fiber and matrix, the interface has an important effect on the physical, chemical and mechanical properties of composites.By means of polarized optical microscope (POM), not only the interfacial morphology but also the bulk morphological features of PET fiber/iPP composites prepared through different preparation methods were investigated. We find that both the PET fibers and the PET particles in iPP/PET blends present a quite strong a-nuclear ability toward iPP and the different shapes of the reinforcements influence the nucleating effect under quiescent conditions in the composite.It was found that PET fibers directly introduced into the iPP melt present a quite strong a-nucleating ability toward iPP. However, for the composites prepared through melt mixing in Haake internal mixer, the nucleating ability of PET fibers and the bulk morphological features changed dramatically, i.e., with the increase of fiber content, transcrystalline layer disappears and the nucleating density in matrix increases steadily. Based on experimental results, different thermomechanical histories involved in sample preparation are proposed to be responsible for such phenomenon.Based on the experimental results, we propose three kinds of nucleation origins to account for the formation of the TCL in our case:(1) fibers acting as heterogeneous nucleating agents; (2) the presence of an interfacial stress between the reinforcements and matrix; (3) lattice match. Though epitaxy is not a necessary condition for nucleation, irregular protruding spots on the surface of PET fibers and particles provided heterogeneous nucleation sites, and simultaneously the thermal stress brings a shearing action in the interphase between the reinforcements and iPP melt, which collectively result in the nucleation and growth mechanism of TCL.