Research On The Preparation And Performance Of PE-based Low-Smoke Halogen-Free Flame-Retardant Cable Materials

Realizing the high performance of polymer and its composite materials through blending and compounding is a key way for the research and application of wire and cable insulation and sheathing materials.In this paper,polyethylene(PE)and its copolymers are used as the matrix,magnesium hydroxide,aluminum hydroxide,magnesium-rich silicon hydrochloric acid(MRS)and additives were added to prepare a series of PE-based low-smoke halogen-free flame-retardant composites by melt blending.The effects of ethylene-vinyl acetate copolymer(EVA),MRS and radiation dose on the thermal stability,crystallization behavior,mechanical properties and flame retardancy of composites were studied.The main content of the paper is divided into the following three parts:(1)PE-based composites with different EVA content were prepared by melt blending,and the effects of EVA content on the thermal stability,crystallization behavior,rheological behavior,insulation,mechanical and flame retardant properties of the composite were studied.The results show that EVA improves the thermal stability of the cable material and reduced the crystallinity of the PE matrix.EVA improves the interaction between the inorganic particles inside the material and the polymer matrix,leading to the increase of G' in the low frequency region of the sample.The addition of EVA reduce the tensile strength of the material.The tensile strength of the material decreased to 11.1 MPa with the content of EVA reaching 20 wt%,but the LOI of the material increased to 26.4%.EVA increases the continuity and compactness of the carbon layer,and improves the degree of graphitization of the residual char of composites after combustion.(2)PE-based composites with different MRS content were prepared by melt blending,and the effect of EVA content on the thermal stability,crystallization behavior,rheological behavior,mechanical and flame retardant properties of the composite was studied.The research results show that MRS increases the initial decomposition temperature of the material,increases the residual carbon content of the material,and reduces the crystallization ability of the material.The introduction of MRS increases the friction between the inorganic particles and improves the G' and G'' of the composites in the low frequency region.The addition of MRS reduces the mechanical properties of the cable material,and the tensile strength and the elongation at break of the composites with 5 wt%MRS were 10.1 MPa and 480%,respectively.MRS has a synergistic flame retardant effect with the magnesium hydroxide and aluminum hydroxide flame retardants,which improved the flame retardant performance of the material,and LOI reaches 28.8%.At the same time,the addition of MRS improves the structural strength of the residual carbon of the material,and there is no dripping during the burning of the material.(3)The irradiable cross-linked PE-based composites were prepared by melt blending,and the effects of different g radiation doses on the thermal stability,crystallization behavior,thermal extension and flame retardancy of the composites were studied.The research results show that the low radiation dose improves the thermal stability of the material,and the cable material has the highest thermal stability when the radiation dose is 15.8 kGy.Low radiation dose reduces the crystalline performance of the PE matrix inside the cable material,while high radiation dose PE will increase the crystallinity.The tensile strength of the cable material cross-linked with low radiation dose is improved,and when the radiation dose is 15.8 kGy,the mechanical properties of the cable material are the highest,the tensile strength and elongation at break are 13.7 MPa and 196%,respectively.When the radiation dose is 21.3 kGy,the elongation of the material under load is the lowest,and the crosslinking degree of the composite is the highest.The LOI of the cable material increases first and then decreases with the increase of the radiation dose.When the radiation dose is 21.3 kGy,the highest LOI reaches 30.2%.