Relationship Between Amount of Scission and Crosslinking Added to Elastomer and Changes in Mechanical Properties

The degradation of mechanical properties of elastomer in an aging process is caused by scission and crosslinking occurred during the aging. In this article the amount of scission and crosslinking was added quantitatively to the elastomer and studied the relationship between amount of scission and crosslinking added to elastomer and the changes in mechanical properties of the sample.

The sample was tetrafluoroethylene-propylene copolymer crosslinked by the irradiation of an electron beam without any additives. The controlled addition of the amount of scission and crosslinking was performed by changes in the dose of ionizing radiation and irradiation condition.

G value (number of molecules changed by absorption of 100 ev) of scission and crosslinking was 0.24 and 1.58 respectively when the sample was irradiated in nitrogen atmosphere at room temperature. G values of scission and crosslinking in air at 100^oC was 1.89 and 0.88 respectively measured by chemical stress relaxation..

Using these results following three conditions was created quantitatively and the mechanical properties were measured. (1) Crosslinking was predominant; ultimate elongation decreased with this operation. (2) Scission was predominant; ultimate elongation increased in early period of this condition, but the value decreased from the certain period. (3) The same amount of scission and crosslinking was added to the elastomer; the decrease in ultimate elongation was very small nevertheless total amount of scission and crosslinking was more than six times of case (1).