Analysis of thermal stability of acrylonitrile‐acrylic elastomer‐styrene terpolymer in injection molding

Abstract

Acrylonitrile‐acrylic elastomer‐styrene terpolymer (AAS resin) was developed to improve weatherability of acrylonitrile‐butadiene‐styrene terpolymer (ABS resin). To compare thermal stability of both resins, test parts of AAS and ABS resins were injection molded at various temperatures and the Izod impact value of the resulting moldings was measured. A study was then made to find the relationship between this value and deterioration of the resins. AAS resin was molded at temperatures from 180°C to 280°C. The impact value of the resulting moldings was almost constant for temperatures up to 260°C, with the first major decrease occurring at 280°C. In contrast, the impact value of conventional ABS resin moldings constantly decreased as the molding temperature was elevated. To explain this phenomenon in both resins, two types of test program steps were undertaken: (1) The cause of the change in characteristics of the AAS resin was determined by obtaining its stress‐strain curve in a high‐speed flexural strength test; measuring its infrared absorption spectrum; and determining its flow properties with a constant‐pressure extrusion type rheometer; (2) the distribution of elastomer in the resin was observed with an electron microscope. It was found that the decrease of impact values of both resins at high temperatures is caused by deterionration of the elastomer. Also, it was found that the different relationships between the impact value and molding temperatures for AAS and ABS resins are due to the difference between the rates of thermal degradation of the acrylic elastomer and butadiene elastomer.

Degradation of ABS in ABS/CaCO₃ Composites during Reprocessing

“…1c is the spectrum of ABS. Many published paper described that the absorption of carbonyl groups and 1, 4-transbutadiene moieties of ABS changed after processing [6][7][8]. ABS is sensitive to oxidation due to the presence of polybutadiene components, which act as oxidation sensitizers and lead to formation of carbonyl groups, which absorb at 1750-1680 cm -1 [9].…”