| Wires and cables play a significant role in the energy and signaling model.Their application range is wider and wider,and the demand is increasing day by day.In this paper,two kinds of polymer materials,resin phase LDPE and rubber phase TPE,were firstly processed into the two-phase polymer as the base material of cable material by the method of polymer melt blending,using the synergistic flame-retardant effect and electron beam radiation crosslinking technology.LDPE has excellent low-temperature tolerance,isolation,constancy,and other properties;TPE has good ductility,bending resistance,heat,and oxygen aging resistance,and so on.According to the characteristics of the two materials,the polymer melt blending method is used to combine the excellent performance of the two and produce a new halogen-free flame retardant cable material with excellent aging resistance and weather resistance,which is in line with the requirements of green and environmental protection in the wire and cable industry.To summarize,this paper is centered at the following three aspects(1)Processing and properties of LDPE/TPE binary blendsTaking full advantage of LDPE/TPE as the basic material,the mechanical,processing,micromorphology,and other conditions of LDPE/TPE under different mixing ratios are directly reflected,and the changes of mechanical properties of blends under different processing conditions are also discussed.The experimental results show that the realistic TS and EB of LDPE/TPE blends are 11.40 MPa and 644.25%The retention rates of the two parameters are increased to 69.32%and 68.21%respectively after thermal oxygen aging,and the performance of the materials is achieved when the processing temperature and time are 140℃ and 10 min respectively The melt index of LDPE/TPE(70/30)blend is 5.83 g/10min,which is better than that of LDPE(1.90 g/10min)and TPE(0.50 g/10min).Blending makes the continuity of products obtained by extrusion processing of materials enhanced.The crystallinity and thermal stability of LDPE/TPE binary blends increase with the increase of LDPE.The fracture surface of LDPE/TPE binary blends is observed by DMA analysis and SEM.LDPE and TPE are compatible after blending TPE have better properties,fewer cracks,and cavities,and TPE forms a three-dimensional network structure in the system,which is beneficial to disperse the effect of external tensile stress and improve the elongation at break(2)Study on the halogen-free flame retardant LDPE/TPE composite with ATHFirstly,the synergistic effect of aluminum hydroxide(ATH)and three synergistic flame retardants(MRP,IFR,OMMT)was studied,the effects of different flame retardant formulations on the mechanical properties,flame retardant properties,rheological properties,thermal properties and dielectric properties of LDPE/TPE binary blends were investigated.The optimum formulation of the compound flame retardant was obtained by the orthogonal test.The test results show that the best physical and fire-resistant properties of the composite are as follows:the addition of flame retardant(phr)is ATH=60,MRP=4,IFR=10,OMMT=10,and the mechanical properties of the whole mixture system can be further improved by making full use of PE-g-MAH as compatibilizer When a certain amount of PE-g-MAH is added to LDPE/TPE composite,it can form a strong chemical bond with ATH in the matrix,increasing The compatibility of ATH and polymer makes ATH inorganic particles and matrix materials closely combined,which plays an enhanced role in composite materials.Besides,after adding PE-g-MAH,the agglomeration of particles in the system is greatly relieved,and the dispersion of matrix is also significantly improved,which makes the stress concentration point of the composite significantly reduced under the external force in the actual application process,and the strength and toughness of the material are further improved.However,if an excessive amount of PE-g-MAH is added,the content of PE in the system will increase significantly,the ductility of the material decreases obviously.When 9 phr PE-g-MAH was added,the TS and EB of the composite reached 10.37 MPa and 185.39%respectively;through the analysis of TG curve,the initial decomposition temperature of the composite material after ATH and MRP,IFR and OMMT were significantly increased,reaching 249.23℃,and the thermal stability was significantly improved;through the observation of the appearance of the char layer after burning,we found that when ATH,MRP,IFR,and OMMT were flame-retardant,After combustion,the materials form a more continuous and compact carbon layer structure,and the isolation effect is significantly improved(3)Study on sensitized radiation crosslinking of halogen-free flame retardant LDPE/TPE compositeThe crosslinking process of halogen-free flame retardant LDPE/TPE composites was carried out by radiation and chemical crosslinking methods at different radiation doses(0-150 kGy)and different peroxide(BPO)respectively The difference between radiation crosslinking and chemical crosslinking was compared by the gel-content test.The effect of chemical composition,crystallinity,and flame retardancy.The results showed that peroxide(BPO)and electron beam irradiation could make the material cross-linked,and the gel content of the composite could reach 58.90%and 69.10%respectively.This indicates that the radiation crosslinking has the merits of high efficiency and no pollution compared with chemical crosslinking.Lower radiation dose(60-90 kGy)can make the composite material achieve higher crosslinking density.It was found that the TS of the composite was increased from 10.37 MPa to 12.26 MPa,and the overall increase was 18.23%.However,the EB of the composite decreased to some extent.The thermostability and fire-resistant properties of the composite were significantly improved after crosslinking at a lower radiation dose(60-90 kGy)When the radiation dose is 90 kGy,the oxygen index of the material reaches 30.10%,and the initial decomposition temperature reaches 263.60 ℃.The results indicate that the electron beam radiation has no negative effect on the compatibility of LDPE and TPE through the appearance analysis of DMA and SEM.The effect of radiation on the crystallinity of LDPE and TPE is studied by X-ray polycrystal diffractometer(XRD),and the thermal properties of LDPE and TPE are also studied by DSC.The results show that the crystallinity of the material decreases after electron beam radiation. |
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