TABLE OF CONTENTS There have been few genuine innovations in antioxidant technology recently. However, a new challenge to antioxidant suppliers in recent years has been the high temperatures generated in the latest automotive, engineering and electrical applications, and in modern electronic equipment. Household appliances such as dishwashers and washing machines present aggressive environments for plastics components because of the combination of heat, detergents and mechanical stress. Oxidation can degrade polypropylene under these conditions. Borealis has developed a stabilised, glass-reinforced PP for washing machine tubs. Some discoloration takes place but this levels off.
Phenolic antioxidants such as bisphenol A and BHT have traditionally been used to protect plasticisers against thermal decomposition in high temperature PVC applications like wire and cable insulation and vehicle parts. This is because branched plasticisers undergo autoxidation and eventually form acids. BHT (butylated hydroxytoluene) is now being replaced in this role by high molecular weight phenols with greater permanence.
Bisphenol A is suspected of having endocrine modulating properties so has been phased out of the polymerisation stage of PVC manufacture in Europe, and Ciba Specialty Chemicals is promoting alternative antioxidants for protecting the plasticiser in flexible PVC as well. One alternative is to use a chain-stopping antioxidant such as Irgastab PVC-11, which has food contact approval.
Two Great Lakes products called Lowilite UV B1260 and UV B1211 have been developed for the protection of PU automotive products against discoloration by heat and light. New additions to the company s Anox TM range (MDAO11...
