Thermal aging of a fluorosilicone rubber

In the present work, the thermal accelerated aging of a fluorosilicone based rubber was investigated at 200 and 250 degrees C under air. The changes in the mechanical behavior of the material were followed by tensile testing. It was possible to observe the embrittlement of the material over aging, mainly with the decrease in ultimate properties, but also with a slight increase in the elastic modulus, indicating a possible crosslinking mechanism in the initial stage of aging. Moreover, it was seen that aged samples had values of elongation at break less than 300% associated with a small weight loss, between 3 and 5%, while the value for unaged samples were 740% +/- 60%. The prevalence of crosslinking is confirmed by DMA analyses, comparing the position and the shape of the tan delta peak at T-g, while the swelling experiments emphasizes the presence of chain scissions, through the changes in the swelling degree and soluble fraction of aged samples immersed in ethyl acetate. The trends observed at 200 degrees C appear to agree with the first stage of aging at 250 degrees C. The degradation mechanisms were also studied with TGA analyses, under either pure oxygen or pure nitrogen, in order to identify the presence of the mechanisms already discussed in the literature: unzipping and oxidation of side groups. The results show a change in the degradation mechanism 200 and 250 degrees C under air, so that unzipping becomes predominant at high temperatures.