Three types of additives for polymers have been studied in polystyrene and poly(methyl methacylate). The effects of a novel thermal stabilizer 3,5-ditertiarybutyl 4-hydroxybenzyl thioglycollate (DBHBT), zinc diethyldithiocarbamate (ZnDEC) have been compared with the commercial antioxidant Irganox 1076. It has been found that the new antioxidant was far more superior to the commercial antioxidant. It also acts as a peroxide decomposer. It also gave considerable synergistic effects with ZnDEC both under thermal and photo degradations. Its use is being recommended instead of the present commercial ones.