Effect of the Filler Modification on the Thermal and Mechanical Properties of Composite Polypropylene/Wollastonite Drawn Fibers.

Polypropylene (PP) is one of the most commercially used thermoplastics, while a significant amount of PP is used in the form of fibers. In this study, the effects of modification of the filler on the thermal and mechanical properties of composite polypropylene/wollastonite drawn fibers were investigated. In this direction, the surface modification of wollastonite with various organic acids, such as myristic, maleic, malonic glutaric, pimelic, and suberic acid, and the use of two solvents were studied. The surface-modified wollastonite particles were used to produce composite polypropylene drawn fibers. The modification efficiency was found to be slightly better when a non-polar solvent (carbon tetrachloride) was used instead of a polar one (ethanol). FTIR experiments showed that myristic, maleic, malonic, and pimelic acid can strongly interact with wollastonite's surface. However, the mechanical strength of the composite fibers was not increased compared to that of the neat PP fibers, suggesting inadequate interactions between PP and wollastonite particles. Furthermore, it was observed that the drawing process increased around 10% the crystallinity of all samples. Wollastonite modified with malonic acid acted as a nucleating agent for β-crystals. The onset decomposition temperature increased by 5-10 °C for all samples containing 2% wollastonite, either modified or not. The suggested modifications of wollastonite might be more suitable for less hydrophobic polymers.