Abstract: 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(ethylene terephthalate), hereinafter sometimes referred to as PET.