subject: Analysis: Radiation cross-linked polyethylene Progress - PE, PE-plastics industry [print this page] 1 Introduction Polyethylene Is widely used in daily life and agricultural production in the polymer. As a semi-crystalline materials, the performance strongly depends on the internal aggregate structure. Polyethylene chain, given the regularity of their good crystallinity, crystallinity can be changed in a wide range. On the other hand, chain and chain binding force between the lack of close, making the polyethylene material withstood the impact of external forces and environmental temperature produces a lower occurrence of deformation or damage, limiting its application. Therefore, the scope and purpose based on the actual application, it is necessary modified polyethylene, cross-linking method is considered effective. Cross-linked polyethylene main use of chemical and physical cross-linking cross-linking. Chemical cross-linking with peroxide and silane for the main Crosslinker . Physical cross-linking is mainly radioactive sources such as nuclear 60Co, 137Cs and neutron, Electronic And other high-energy particle radiation or radiation crosslinking. 1952 Charsby [1] found that irradiation produced a cross-linked polyethylene, cross-linking of polyethylene from booming. The rapid development of high-energy radiation device for an objective study of radiation cross-linking provides a solid foundation. Currently, irradiation, application of technology and tools have been applied as a measure of a country's high level of one of the symbols. The application of radiation in polymer mainly radiation and radiation crosslinking polymerization. Polymer produced by the radiation properties of significant changes, mainly occurring within the cross-linking and degradation. Chemical crosslinking with radiation crosslinking approach to performance from implementing the changes were different. As a result of chemical cross-linking cross-linking agent, a rich source of easily obtained, are more widely used. As the polymer cross-linking reaction, the constant increase in the melt viscosity so that cross-linking agent dispersed in the matrix of the poor, which have uneven crosslinking occurred there, "scorch" phenomenon. Chemical cross-linking agent, especially peroxides decomposition temperature and melting temperature of the polymer close, inevitably in the processing time to peroxide loss is difficult to control the degree of crosslinking; and the decomposition of silane crosslinking Water do initiator, due to water intrusion, degradation of dielectric properties, to a certain extent, limited its application. Radiation cross-linking by high-energy radiation sources can be given effect in the material evenly, cross-linked polymer distribution and degree of crosslinking is easy to control, to meet the requirements of polymer crosslink in high places. Another unique feature of radiation crosslinking is no need to add cross-linking agent, cross-linked product of high purity, especially in the field of medical polymer materials and their huge potential applications. However, the different types of polymers result by the role of different rays. Polymer can usually occurs under irradiation crosslinking, degradation may also occur. Accordingly, the polymers can be divided into radiation and radiation degradation of crosslinked type. Strictly speaking, the crosslinking reaction when irradiated with the degradation process is at the same time competition. Even the radiation crosslinking of the polymer, its internal radiation crosslinking and radiation degradation is at the same time, the only cross-linked dominant only. The occurrence of cross-linking and degradation as well as competitive rate than both the structure and the polymer itself is also imposed by the external radiation dose, dose rate, radiation environment (temperature, atmosphere) and so on. So far, the radiation crosslinking technology for cross-linking process of polymer materials and the most typical example is the radiation crosslinking of polyethylene. XLPE shows a series of outstanding chemical and mechanical properties of (heat resistance, dimensional stability, suitable modulus, resistance to stress cracking a significant improvement). In recent years, cross-linked polyethylene irradiated deepening theoretical and applied research, for irradiation in the synthesis and modification of new materials to develop a new approach. This basic principle of its response to irradiation, irradiation of the polyethylene structure, properties and application prospects are reviewed. The basic principles of 2 2.1 cross-linking reaction Polyethylene by high energy radiation, in addition to CH, on the side of the base or free radicals, the macromolecular chains were broken into radical, radical combination between the Health Alliance network transactions. Crosslinked molecular chains can form H and Y (or T) of the body structure [2]. Crosslinking process and the relationship between polymer structure, according to radiation doses from low to high, can be divided into four stages [3]: (1) cross-linked by the end of the initial stage of the main effects of groups, as an ordered cross-linking;
Analysis: Radiation cross-linked polyethylene Progress - PE, PE-plastics industry
