Molecular simulation of interaction mechanism between wollastonite and stearic acid and use of modified wollastonite powder as filler in polyamide 6 and polypropylene

Abstract

The physical and chemical properties of wollastonite were optimized by dry modification using stearic acid, and the influence of the stearic acid dosage on the modification effect was explored. The surface functional groups of the modified and unmodified wollastonite powder were characterized using infrared spectroscopy, and a molecular simulation was employed to evaluate the micromechanism of the stearic acid-modified wollastonite. The surface of the wollastonite is most active when a single hydroxyl group is bound to its surface and the hydroxyl group does not attract the atoms of wollastonite itself. A C–O–Ca bond is formed between the stearic acid and wollastonite, and in terms of the activation index, the optimal stearic acid dosage is 1.5 %. Composite materials were prepared by filling polyamide 6 (PA6) and polypropylene (PP) with the unmodified and modified wollastonite powders, and the impact strength, tensile strength, bending strength, and other indicators of the composite materials were tested. The PA6 and PP samples filled with unmodified wollastonite showed improved rigidity but lower toughness compared to the pure PA6 and PP samples. In contrast, using the modified wollastonite as a filler simultaneously improved both the rigidity and toughness of the PA6 and PP samples.