The accelerated weatherability methods and the chemical analytical methods of polyurethane sealants for buildings have been investigated. The chemical composition of sealants has been analyzed by using the solvent extraction technique. The amount of plasticizer has been measured using by n-hexane as an extraction solvent, and that of non-crosslinked poly-urethane and cross-linked polyurethane using by N,N-dimethylformamide as an extraction solvent. According to the results of the measurement of weathered polyurethane sealants, it was cleared that the amount of plasticizer decreased and the amount of non-crosslinked polyurethane increased with increas-ing weathering time. In order to develop a relevant accelerated weathering conditions, the factors of temperatures and humidity have been examined. The state of weathered sealant at temperature of 80°C and relative humidity of 5%RH was similar to that of outdoor exposure sealants, and the acceleration factor was calculated as about 16. Furthermore, analyzing by means of Py-GC/MS method, it was confirmed that the amount of diisopropylether of weathered samples was larger than that of an initial sample. The decomposition of crosslinked polyether-polyurethane was assumed to be caused by oxidative cleavage of the polyether segment.
It was confirmed that the trans chains of PE molecular chains, to which Li2CO3 was added (PE with Li2CO3), transform to gauche chains, and as a result, maltese crosses disappeared. We investigated changes in the suscep-tibility of PE to thermal oxidation with the transformation of PE molecular chains to gauche ones. Furthermore, the study by Py-GC method on the gases evolved by the oxidation of PE showed that the amount of CO gas evolved in PE with Li2CO3 is reduced compared to PE without Li2CO3 , indicating that the addition of Li2CO3 to PE is presumed to have the retardation effect for the oxidation. The amount of CO gas evolved in PE with Li2CO3 by heat treatment at 110°C for 1 to 5hr was less than that of PE without Li2CO3. This result also seems to be originated in the retardation effect due to Li2CO3 Among PE with Li2CO3 examined in this study, the smallest amount of CO gas evolved was recorded for PE to which Li2CO3 of 1.0 part per hundred resin was added, so it is expected to have the largest retardation effect for the oxidation.