The effect of gamma irradiation in air and inert atmosphere on structure and properties of unfilled or glass fibre-reinforced polyamide 6

Abstract

Crosslinking of polyamide 6 (PA) and filled one with glass fibres (PA/GF) was initiated via macroradical formation by gamma irradiation either in air or in inert argon atmosphere. The crosslinked portion was found to start at absorbed dose around 300 kGy and achieved about 60 and 40 wt% for PA and PA/GF, respectively, if irradiation proceeded in inert, while in air molecular weight increase was only observed without crosslinked gel formation. DSC indicated that irradiation leads to a decrease in crystallinity as well as lamellae thickness. Besides crosslinking, scission of polymer chains also occurs. Modest increase of impact strength was found for PA while small decrease for PA/GF was observed. The dependence of Young’s modulus values on the irradiation dose indicates a minimum around gel point being more pronounced for PA compared to the composite. Irradiation resulted in minor changes in tensile strength and elongation at break while a substantial increase in the elongation at yield was found for PA if irradiated in inert atmosphere. Generally, the application of an optimal dose of gamma irradiation in air results in an increase of toughness of PA without changing other mechanical properties.