The article proposes a new representative of the property for estimating the life time of elastomers. The method takes the area of stress-strain curve that is obtained by the tensile test as tensile energy (TE), and TE is defined as the representative of the property of elastomers. To investigate the changes in mechanical properties, eleven kinds of ethylene-propylene elastomer (EPR) was aged by 'γ ray irradiation at 70°C. The ultimate elongation and tensile strength did not always decrease with increasing dose. On the other hand, TE of EPR decreases as increasing dose for all the samples. The relationship between the values of TE and logarithm of dose was on the straight line or on the composition of connected two straight lines. Therefore, TE is useful representative of property for estimating the life time of elastomers.

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Polycarbonate parts for railway track fastenings fractured when they are continuously subjected to the stress in the condition of contacting with water-proof oil components. In this paper, the cause of the fracture has been studied. For the analysis, New C-type Creep Method established by the author is used taking S.S.C. Creep Index as a measure. The reason why polycarbonate fractured in the railway track was synergistic effect by the actions among DMP, glycol and the corrosion inhibitor (ether type) for the polymer, combined with the interaction between the stress and these reagents.

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