Thermo gravimetric analysis of expendable pattern casting adhesives

摘要

Expendable pattern casting (EPC), currently referred to as lost foam casting, is a cost-effective process for the high-volume manufacture of castings with complex cavities and thin-wall sections. Adhesives used in bonding foam pattern assemblieshave not received much attention. Currently, no accepted method of monitoring these adhesives for quality control exists. During high-volume production, EPC adhesives are held at elevated temperatures for weeks, while being exposed to the atmosphere. Theeffects of such conditions, over time, are not understood. The purpose of this study was to determine if thermo gravimetric analysis (TGA) is an acceptable method for monitoring EPC adhesives, and to determine if prolonged atmospheric exposure at certaintemperatures has any effectComparisons of TGA results from "virgin" and "old" EPC adhesive samples identified a change in the material, over time. One method of TGA investigated (ramped heating) was found to be an acceptable method for monitoring EPC adhesives for certifying aspecific lot of material, as well as assuring the quality of the material in use, over time. Degradation in the EPC adhesive exposed to O{sub}2, while held at a temperature of 138C was detected using TGA. Standard test parameters for TGA of EPC adhesiveswere proposed by the author for quality control applications.