Comparison of natural and synthetic wollastonite modifying action in epoxy polymers

Natural wollastonite is an effective filler of epoxy adhesives and coatings, due to its micro-reinforcing action caused by the needle shape of particles. At the same time, its natural reserves are not enough to meet the needs of industry on a global scale. This makes relevant research on the production of synthetic wollastonite, especially based on annually renewable, vegetable raw materials, for instance rice husk ash, rich by silicon dioxide. Based on rice husk ash and limestone, wollastonite samples were synthesized with a different ratio of initial components. Their modifying effect in amine-cured epoxy compositions has been studied in comparison with natural wollastonite. The obtained results suggest that both natural and synthetic wollastonite increase wear resistance and hardness of epoxy coatings. These effects depend on the ratio of silicon oxide and calcium carbonate in the synthesized fillers and higher with the highest content of β wollastonite, having a needle-like particle shape. This is achieved with the molar ratio of СаСО₃ and SiO₂ о/1.2 : 1, which has been found to be optimal.

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