No abstract

Introduction. Polymeric materials exposed to heat, mechanical stress, and ionizing or UV irradiation undergo degradation in the presence of oxygen due to the formation of reactive intermediates such as free radicals R • , RO • , and ROO • and hydroperoxides ROOH. 1-10 The degradation process can be accelerated by chromophores, free radicals, and metallic residues from the polymerization reactions. The structural and morphological changes in the polymer properties due to exposure to environmental factors are often profound and include modification of the chemical structure (for instance, formation of double bonds, chain scission, and cross-linking) and loss of crystallinity, especially at large radiation doses. Often the deleterious effects are not immediately detected but develop over longer periods. The gradual changes in the polymer properties observed in many systems including polyolefins, and the ultimately grave results, are due to trapped radicals that react slowly, to peroxy radicals that decompose in time with formation of reactive radicals and gas molecules, and to trapped gases that lead to local stresses and to cracking. 3,9 While the time scale of these changes may vary, the final results are dramatic: degradation of the structure and collapse of the mechanical properties. The accelerated rate of ozone depletion in the stratosphere due to environmental factors is expected to raise the level of UV-B radiation (λ ) 290-320 nm), thus adding severity to the problem of degradation and urgency to the need for solutions.Hindered amine stabilizers (HAS) rank among the most important recent developments for light and heat stabilization of polymeric materials. Nitroxides and hydroxylamine ethers are the major products of reactions involving HAS. The HAS-derived nitroxides are thermally stable but can react with free radicals (as "scavengers") to yield diamagnetic species; the hydroxylamine ethers can regenerate the original nitroxide, thus resulting in an efficient protective effect. 6,9 The pivotal role of nitroxides (added as such or derived from HAS) has been documented recently in low-molecular-mass model systems. 7 In polymers the situation is more complicated, and the equilibrium concentration of the nitroxides varies markedly with the nature of the polymer matrix, thermal history, humidity, and type of

In this paper, glycolysis of toluenedilsocyanate based water-blown polyurethane foam has been examined by high performance liquid chromatography and gel permeation chromatography to determine the product distribution. Glycolysis with diethylene glycol (DEG) yields toluenediamlne (TDA), TDA mono-and di-DEG carbamates, a series of urea-linked mono-and di-DEG carbamate TDA oligomers, and polyether triol (polyol). The complexity of the product mixture suggests problems In applying simple glycolysis to the recovery of mixed and/or contaminated polyurethane wastes. A simpler product mixture results when water and a base catalyst are added to the glycolysis reaction (hydroglycolysis). Hydroglycolysis yields TDA and polyol as principal products. Data for the rate of the hydroglycolysis reaction are presented In the temperature range of 150 to 190 °C. These results suggest that hydroglycolysis could be used to recover polyols from mixed and/or contaminated water-blown polyurethane wastes.

No abstract