The dielectric and mechanical properties of a potassium-titanate-whisker-reinforced PP/PA blend

A group of polypropylene/polyamide/potassium-titanate-whisker (PP/PA/whisker) composites was prepared by means of a Haake mixer. The whisker surface was modified using either a silane or a titanate coupling solution. The effects of whisker surface modification and whisker content on the dielectric and mechanical properties of the composites were then studied. Results show that whisker-surface modification has a remarkable influence on the properties and a properly selected coupling agent can effectively improve the dielectric stability of the composites under moist conditions. It was also found that both mechanical and dielectric properties increased with whisker content below additions of 20 phr whiskers into the PP/PA blend. However, property deterioration was observed when the whisker content was above this level. This was particularly true when water-treated specimens were tested. Microscopy studies revealed that the composite had a continuous PP phase and a dispersed PA phase. The whiskers were embedded in the PA particles exclusively at 20 phr or below. It is believed that this microstructure was caused by the strong interaction between the surface-modified whiskers and the polar PA molecules and may be responsible for the property transition observed in dielectric and mechanical tests.