linear polymer resins composed of repeating hydrocarbon units linked together by ester or amide linkages are treated with a liquid or gaseous primary or secondary amine under thermal conditions which cause aminolysis of some of the linear linkages to produce polymer resins of reduced average molecular weight . the procedure is applicable to polyesters , such as polycarbonates and polyterephthalates , and to polyamides , such as nylon 66 , nylon 6 , nylon 11 and nylon 12 . the process is particularly applicable to the recovery or recycling of throw - away bottles made of poly , hereinafter sometimes referred to as pet .