Crosslinking of Trans-1,4-polyisoprene by γ-ray radiation

Abstract

This work investigates the effect of γ-ray radiation on the chemical, thermal, and mechanical properties of trans-1,4-polyisoprene (TPI). The radiation dose covers a broad range of 0 ∼ 1000 kGy. Two different atmospheres, nitrogen (N2) and air, are comparatively studied. The results indicate that TPI can be crosslinked effectively by γ-ray radiation, evidenced by the fact that the gel content of the irradiated TPI reaches as high as 96%. The crosslinking degree reaches as high as 325 mol/m3. Slightly higher gel content is obtained for TPI irradiated in N2 as compared to that irradiated in air. Fourier transform infrared spectra (FTIR) indicate the formation of -C=O and –OH groups of TPI irradiated in air. The spatial distribution of oxygen-containing groups in the samples induced by diffusion-limited oxidation is characterized by micro-FTIR mapping technique. The initial TPI samples contain mainly the α phase. After irradiation and melting, they recrystallize into the β phase. With the increase of absorbed dose, the melting temperature, crystallization temperature, crystallinity, yield strength, and elongation at break of the samples decrease, while the strain recovery increases. Electron paramagnetic resonance results confirm the spices of the radicals in the irradiated TPI.