Surface and adhesive properties of low-density polyethylene after radiation cross-linking

Abstract

Radiation cross-linking gives to inexpensive commodity plastics and technical plastics the mechanical, thermal, and chemical properties of high-performance plastic. This upgrading of the plastics enables them to be used in conditions which they would not be able to with stand otherwise. The irradiation cross-linking of thermoplastic materials via electron beam or cobalt 60 (gammy rays) is performed separately, after processing. Generally, ionizing radiation includes accelerated electrons, gamma rays and X-rays. Radiation processing with an electron beam offers several distinct advantages when compared with other radiation sources, particularly γ-rays and x-rays. The process is very fast, clean and can be controlled with much precision. There is no permanent radioactivity since the machine can be switched off. In contrast to γ-rays and x-rays, the electron beam can steered relatively easily, thus allowing irradiation of a variety of physical shapes. The energy-rich beta rays trigger chemical reactions in the plastics which results in networking of molecules (comparable to the vulcanization of rubbers which has been in industrial use for so long). The energy from the rays is absorbed by the material and cleavage of chemical bonds takes place. This releases free radicals which in next phase form desired molecular bonds [1,2,3,4]. This article describes the effect of radiation cross-linking on the surface and adhesive properties of low-density polyethylene. The best results were achieved by the irradiation with doses of 165 and 198 kGy. The strength of bonded joints after irradiation was increased up to 250 % compared to untreated material. A similar trend was observed even for surface energy and crystallinity of the material. © (2014) Trans Tech Publications, Switzerland.