Application and characteristics of talc in food grade grease

The 2021 Green Mine Science and Technology Award (non-metallic ore, mineral material related fields) application work is organized and reviewed by the Zhongguancun Green Mine Industry Alliance Non-metallic Mine Special Committee, please pay attention to the V letter public number "Powder Technology Network".

　　Food safety issues have always been the focus of people's attention, and there are many factors affecting food safety, among which pollution caused by leakage of lubricating materials in food equipment is one of the important reasons. Food-grade greases are widely used in key transmission parts of food processing equipment such as bearings, chains and rails, and the lubricating properties of greases depend mainly on the additives used.

　　

　　In view of the safety of food-grade grease, non-toxic and harmless are the primary considerations when selecting additives. Food grade talc as a food additive, often used in food flow and mold release; because of its good lubrication properties, it also has certain applications in the field of tribology, such as applying talc powder to protective clothing, so as to reduce the skin damage of medical staff during COVID-19; in addition, talc powder in lubricating oil has excellent anti-friction properties, which can better reduce the wear of cast iron equipment.

　　Gong Longfei et al. prepared composite aluminum-based greases by white oil and thickeners, and investigated the influence of the mass fraction of food grade talc on the tribological properties of greases, and the results showed that:

　　(1) Talc can improve the thermal stability performance of composite aluminum-based grease, and the epitaxial decomposition temperature of base grease is significantly lower than that of grease containing talcum powder;

　　(2) Talc can improve the tribological properties of composite aluminum-based grease, that is, improve the stability of the friction process, reduce the friction coefficient and wear volume; with the increase of talc mass fraction, friction coefficient and wear volume have undergone changes that first decrease and then increase, and when the mass fraction of talc is 1.0%, the average friction coefficient and wear volume are minimal; talc can form a dense lubricating film on the surface of the friction pair, and some talc powder plays an effective anti-friction and anti-wear effect by repairing wear marks and micro-polishing;

　　(3) Grease added with talc with a mass score of 1.0% is most likely to be applied to food equipment and other fields.

　　(4) Talc belongs to the layered silicate, which can be adsorbed on the surface of the friction pair during the friction process, which is equivalent to the "sliding bearing" for slippage, so as to reduce friction and reduce wear.

　　(5) From the perspective of the thermal stability performance of the grease, when the termination degradation temperature is reached, the remaining weight of the grease sample containing talc is higher than that of the base grease, which is due to the fact that the main components of talc are MgO and SiO2, of which the thermal stability of SiO2 is better and can improve its thermal stability performance. Due to the easy generation of a large amount of heat during the friction process, SiO2, which has good thermal stability, is easy to stay in the gap of the friction pair. Due to the surface roughness of the steel plate, the real contact area between the steel ball and the steel disc is small, and the contact stress between the steel ball and the steel disc is small, which is easy to produce larger friction and produces a gully on the surface of the wear mark, so some talc (mainly SiO2) can repair the grooves generated by the wear mark surface during the friction process, thereby increasing the contact area between the friction pairs and reducing the contact stress between the friction pairs; at the same time, SiO2 is a commonly used polishing material, so a trace amount of SiO2 can produce a micro-polishing effect on the friction pair surface. Thus achieving the effect of reducing friction and reducing wear.

　　Source: Gong Longfei, Qian Shanhua, Wang Wei, et al. Effect of food grade talc on tribological properties of composite aluminum-based grease[J].Journal of Tribology: 1-15[2021]", edited by [Powder Technology Network], please indicate the source!