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Thermal Stability of Polyurethane Elastomers Before and After UV Irradiation

In this work we investigated the thermal degradation behaviour of the segmented polyurethane, PUR, elastomers before and after UV irradiation. The thermal degradation of PUR elastomers was studied over the temperature range of 25-600oC in an atmosphere of nitrogen using thermal gravimetric analysis (TGA). Four series of polyurethane elastomers derived from poly(oxytetramethylene) glycol, PTMO, of 1000 and 2000 molecular weight and polycaprolactone glycol of 1250 molecular weight, PCL, 4, 4’diphenylmethan diisocyanate, MDI, and 4, 4’-dicyclohexylmethane diisocyanate, H12MDI, and 1, 4-butanediol as chain extender, were synthesized by the prepolymer method. The derivative thermo gravimetric (DTG) peaks observed in the experiments indicated that PUR elastomers degraded through two-steps. We attributed the first step to degradation of hard segment. The second degradation step could be ascribed to degradation of soft segment. We found that the PUR elastomers based on polyester polyol and aromatic diisocyanate exhibit better thermal stability than PUR elastomers based on polyether polyol soft segment in both steps of degradation. The thermal degradation is more prevalent in PUR elastomers based on cycloaliphatic diisocyanate. The higher values of temperature of initial decomposition, Ti, indicate a higher thermal stability of UV exposed elastomers on the beginning of degradation. This may be due to the formation of crosslinking structure in the presence of UV irradiation.

Segmented polyurethane elastomers; thermal degradation; thermal gravimetric analysis; thermal stability

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