SEDL / STP / STP997-EB / STP26399S

Thermogravimetric Analysis of Sheet Molding Compound Materials to Determine Distribution of Compound Components in Molded Parts

Allen, PJL
Research associate, Premix, Inc., North Kingsville, OH

Pages: 15    Published: Jan 1988

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Abstract

Thermogravimetric (TG) analysis was used to investigate localized differences in the composition of complex parts molded from sheet molding compound (SMC). Localized differences in composition may arise as the SMC encounters flow restrictions in the mold such as bosses, ribs, and other design features. Conventional SMC is comprised of both mineral fillers and glass reinforcements. Therefore, preliminary work to develop equations relating weight loss to specimen composition and to define significant differences in composition was accomplished using comparisons of matrix and glass reinforced samples. Part sections taken from restricted flow areas of a complex part were then analyzed and SMC charge patterns were varied to evaluate their effect on localized composition. The information collected demonstrates that TG analysis is a viable technique for examining flow restrictions in the molding of SMC.