PROCESSING-INDUCED CRYSTALLIZATION OF SEMICRYSTALLINE POLYMER NANOCOMPOSITES

摘要

It is clear from the literature that nanoparticles can drastically alter the development of crystalline morphology within semicrystalline polymer nanocomposites. For example, nanoparticles may act as heterogeneous nuclei and hence increase the nucleation rate, leading to a decrease in crystallite sizes, changes in crystalline structure, and in some cases increase the overall degree of crystallinity (dependent on factors such as the polymer type, structure, and polymer molecular weight). Such changes in crystalline morphology can typically be observed under quiescent conditions; however, realistic nanocomposites based on engineering polymers manufactured via melt-processing are subject to a much more complex thermo-mechanical history during which the macromolecules undergo relatively high rates of shear and extension followed by rapid quenching. Working with several high performance engineering thermoplastics (such as PBT, PVDF, PEEK, and nylon), the processing-induced crystallization of these nanocomposite systems has been studied under both externally-applied shear and pressure loadings at temperatures above the crystallization temperature of the nanocomposites. Several results are presented to illustrate how nanoparticles, even at very small loadings, can drastically alter the processing-induced crystallization of semicrystalline polymer nanocomposites. The implications of such results on the processing of these material systems will also be highlighted.