Effects of processing conditions on properties of nano-SiO2/polypropylene composites fabricated by pre-drawing technique

To improve the performance of nanoparticles/thermoplastics composites, a pre-drawing technique was developed in the authors’ lab. Nanoparticles were firstly modified by graft polymerization, and then the grafted nanoparticles were melt-compounded with a matrix polymer and stretched to produce composite filaments. Finally, the filaments were injection molded into bulk materials. Because the filamentation-induced separation of the nanoparticle agglomerates can be kept in the course of re-molding due to the interaction between the grafted polymer and the matrix, the nanoparticles were uniformly dispersed in the ultimate composites. As a result, an overall enhancement of tensile and notched impact properties of the composites was acquired. The present work systematically investigated influences of the key factors (percent grafting of the grafted nanoparticles and draw ratio) on structure and properties of nano-SiO2/polypropylene composites. It was found that draw ratio set for filamentation should match the amount of the grafted polymer (i.e. percent grafting) for purposes of giving full play to the pre-drawing technique. The composites’ microstructure and performance as well could be tuned by changing the processing conditions.