PP/LDPE blends filled with short polyamide fibers

The effect of short polyamide 66 (PA) fibers on the tensile, flexural, and impact behaviour of low density polyethylene (LDPE), polypropylene (PP), and their blends has been investigated. The moduli of the composites increase as fiber and PP contents increase, and this effect is more noticeable at LDPE/PP ratios above 1. However, the effect of the fibers on the tensile and flexural strength of these materials depends on matrix composition. So, the polyamide fibers act as a reinforcing agent for polymer matrices with LDPE/PP ratios above 1, but with PP as the continuous phase a decrease in the tensile strength is observed. In all cases, at the same fiber content, the strength of the composites increases as PP percentage increases. On the other hand, the addition of PA fibers gives rise to an increase of the tenacity of the composites with PP percentages above 50% in the matrix composition. From the observed results a higher reinforcing effect and a better affinity between the polyamide fibers and the LDPE are suggested.