To investigate the grain-size and phase compositions and properties of natural and synthetic wollastonite fillers and to establish the nature of their modifying effect in polymer composite materials using the example of polyvinyl chloride thermoplastic and epoxy resin thermoset.
Methods. X-ray quantitative phase analysis was used to study the filler samples, and porosity was determined using mercury porosimetry and gas absorption. The particle size of wollastonite was determined by laser diffraction. The thermal stability of the filled composites was evaluated on a derivative thermogravimetric analyser, and the thermal stability of polyvinyl chloride materials was evaluated using the Congo red method. Dynamic mechanical analysis was performed on a DMA 242 Netzsch device.
Results. The particle size distribution and phase composition of natural and synthetic calcium silicate samples, their porosity and pH of aqueous extract were studied. The influence of wollastonite properties on the viscosity of the obtained polymer-filler mixtures, the thermal stability and wear resistance of the filled composites, as well as on the tensile strength and relative elongation of polyvinyl chloride compositions was established.
Conclusions. Studied calcium silicates have proven effective for both epoxy and polyvinyl chloride materials. Despite the similarity in phase composition and acid-base characteristics of the surface, natural and synthetic wollastonite differ in particle size distribution and porosity. Natural filler is more promising for creating heat-resistant polyvinyl chloride compositions and wear-resistant epoxy compositions, while synthetic wollastonite based on rice husks provides an increase in the dynamic modulus and glass transition temperature of both types of polymers. Studies have shown that the modifying effect of the studied fillers is more prominent in epoxy polymers due to their influence on the formation of the polymer matrix cross-linked structure.