Carboxylic End Groups

Hydrolytic Stability

The number of acidic sites present in the resin determines its susceptibility to water at high temperatures. Moisture reacts at these locations to cleave the chain, reducing the molecular weight and the physical strength of the part. Low initial counts are preferred for materials that will undergo multiple heat cycles.

Melt Viscosity

Shorter chains with more acid ends result in a thinner melt that may leak from the mould or cause flash. Consistency in the count of these groups ensures that the moulding process remains stable over a long production run. Processors adjust the drying time to prevent further formation of these groups during the melt phase.

Variations in viscosity lead to inconsistent part weights and dimensional errors in precision components.

Processing Risk

Elevated levels of acid ends act as a catalyst for further degradation, creating a self accelerating cycle of material failure. Blending virgin resin with regrind requires a careful check of the total acid content to avoid brittle parts.