Study On Enhanced Performance Of EVA Composites For Cables

The polymeric composites with enhanced performance prepared by blending and compounding methods is an important research direction in the manufacture of insulation and sheath for special wire and cable.In this dissertation,ethylene-vinyl acetate copolymer（EVA） is used as the substrate,magnesium hydroxide（MH） and aluminum hydroxide（ATH）are used as flame retardants,and silica（SiO₂） is used as reinforcing filler.A series of EVA based composites were prepared by melt blending and hot pressing.Firstly,the high-elastic rubber and the functionalized polyolefin were introduced into the above system,respectively,to study the effects of the two on the condensed structure and on the properties of the composites.On this basis,a new functionalized ionic liquid（IL） was introduced into the EVA based composites.The effects of IL on the condensed structure and properties of composites has also been investigated.The main contents are described as the followings:（1）The highly elastic rubber is ethylene-methacrylate rubber（AEM）.It was found that the high content of AEM can deteriorate the processability of the composites.DSC tests showed that AEM will decrease the glass transition temperature of the matrix,indicating the interaction between AEM and matrix.However,TG results indicated that AEM will thermally stabilize the composite.SEM showed that the introduction of AEM in the EVA based composite system caused the further agglomeration of inorganic particles and the decrease in interfacial adhesion between the inorganic particles and the polymer.Due to the high content of AEM,the mechanical strength,oil resistance and insulation performance of the composites were reduced owing to damage of the internal phase interface structure of the composites.（2）The functionalized polyolefin is a glycidyl methacrylate grafted ethylene-octene copolymer（POE-g-GMA）.It was found that POE-g-GMA had no adverse effect on the processability.The results of TG test showed that POE-g-GMA is beneficial to the improvement of thermal stability of composites,that is,the initial decomposition temperature T_5% moved to the high temperature zone with the increase of the compatibilizer content.SEM images proved that POE-g-GMA can alleviate the agglomeration of inorganic particles and improve the interfacial adhesion between the particles and the matrix.Besides,rheological behavior analysis showed that POE-g-GMA can promote the formation of solid network structure inside the composite.Thanks to the enhanced structural stability of the internal interface,the mechanical properties,oil resistance and insulation properties of the composites were great improved.Moreover,the carbon layer obtained by the combustion has small defects and an increased degree of compactness.（3）A novel ionic liquid（IL） was synthesized by using 1-vinylimidazole and tris（2-chloroethyl）phosphate as raw materials.The gel content test showed that IL could increase the degree of crosslinking of the composites.TG results showed that IL could catalyze the formation of the carbon to promote the increase of residual carbon.Besides,IL also has a certain effect to improve the particle dispersion.In addition,IL is beneficial to form a dense and continuous carbon layer structure to improve the flame retardancy and thermal stability of the composites.In concusion,IL can achieve the common improvement in overall performance such as mechanical,flame-retardant,oil-resistant and other properties.