Mechanisms of antioxidant action: Autosynergistic polymer-bound antioxidants as heat and light stabilizers for ABS

An antioxidant (3,5-di-tert-butyl-4-hydroxybenzyl mercaptan) and a u.v. stabilizer (4-benzoyl-3-hydroxyphenyl-O-ethylthioglycollate) containing the thiol group have been reacted with ABS latex to give polymers with exceptionally high heat and light stability. Both chemical and physical phenomena contribute to the high activity of the bound antioxidants. The concentration of the molecularly dispersed antioxidants in the most oxidatively vulnerable part of the polyblend (the polybutadiene segment) has an important role in determining stabilizer efficiency and, particularly under high temperature conditions, the immobilization of the antioxidants by chemical bonding leads to much lower rates of physical loss. The autosynergistic hindered phenol is primarily responsible for the thermal stabilizing activity of the combination but it also powerfully augments u.v. stabilizing effectiveness of the u.v. stabilizer.