Study of Physical and Chemical Processes Occurring During Polycondensation of Bakelite Binder in Order to Adjust Technological Process of Abrasive Tool Production

摘要

Abrasive-bakelite compositions after molding are subjected to heat treatment (bakelization) to cure the ligament. The process of binder curing at temperatures up to 190°C is accompanied by the release of gaseous substances, mainly water vapor, which is contained in liquid bakelite (up to 27%) and ammonia, which is formed at 120°C during the heat treatment of the instrument during the decomposition of hexamethylenetetramine (urotropine), which is contained in powder binder. Water vapor, withdrawing from the volume of the wheel during heat treatment under pressure, destroys the structure of the product, and increases the volume, which manifests itself in the form of bulges, shells, and bundles. This in turn leads to a decrease in the density, and physical, mechanical, and operational properties of the abrasive. A technological adjustment is needed to increase the mechanical strength of the instrument. The emission of volatiles in the bakelization process in the raw materials and molding sand mixture of face grinding wheels was determined. The processes occurring in certain temperature ranges of bakelization were also analyzed.