XLPE

Cross-linked polyethylene is a method of polyethylene modification. Commonly used cross-linked polyethylene in industry includes radiation cross-linked polyethylene, peroxide cross-linked polyethylene and silane cross-linked polyethylene. Polyethylene (LDPE, HDPE, Both LLDPE and MDPE) can change their physical and mechanical properties through cross-linking, which can cause partial cross-linking reactions between macromolecular chains. PEX is the abbreviation code for cross-linked polyethylene.

Cross-linked polyethylene is a thermosetting plastic with a network structure. After the cross-linked polyethylene product is formed, it cannot be molded again. At this time, it can also be machined.

Cross-linked polyethylene is non-toxic, odorless, non-absorbent; wear resistance, solvent resistance, stress crack resistance, weather resistance, aging resistance and dimensional stability are very good; low temperature softness and heat resistance are good, and can be used in Long-term use below 140°C, the softening point can reach 200°C; impact strength, tensile strength, creep resistance and rigidity are better than HDPE; it has good electrical insulation, low temperature resistance, chemical stability and radiation resistance Performance; the film formed by cross-linked polyethylene is thin, transparent, and has good water vapor permeability; after cross-linked polyethylene is heated, inflated (stretched), cooled and set, when reheated to above the crystallization temperature, It can naturally return to its original shape and size.

Cross-linked polyethylene can be used to form products by extrusion, and can also be used to form products by injection, molding and other methods. The extruder can be used to extrude heat-resistant pipes, hoses, heat-shrinkable films, sleeves, wires, cable coatings, etc.; the injection molding machine can be used to inject high-pressure, high-frequency heat-resistant insulating materials, and chemical equipment. Corrosion-resistant parts, containers and foam plastics, etc. For example, Sanren brand XLPE, DJ200 and DJ210 produced by Shanghai Petrochemical Company are special materials for extruder forming cross-linked cables.

Ethylene-vinyl acetate copolymer

Ethylene-vinyl acetate copolymer (EVA or E/EVA) is also called ethylene-vinyl acetate copolymer, which is prepared by copolymerizing ethylene (E) and vinyl acetate (VA).

performance characteristics

Products molded by EVA resin have good softness and elasticity, and they still have good flexibility in an environment of -50°C, have good transparency and surface gloss, are non-toxic, have good chemical stability, and have strong anti-corrosion properties. Aging and ozone resistance; good blending with other fillers, good coloring and molding processability. The performance of EVA is greatly related to the content of vinyl acetate, molecular weight and melt flow rate value. When the MFR is constant, as the content of vinyl acetate increases, its elasticity, flexibility, compatibility and transparency are all improved, but the crystallinity decreases; if the content of vinyl acetate decreases, its performance is close to that of polyethylene, but its Rigidity, abrasion resistance and electrical insulation properties are improved. If the vinyl acetate content is fixed, when the MFR value increases, the softening point decreases, the processability and surface gloss are improved, but the mechanical strength decreases; if the MFR value decreases, the molecular weight increases, and the impact performance and stress cracking resistance has seen an increase.

Molding method and use

EVA resin can be formed into products by injection molding, extrusion molding, blow molding, calendering, rotational vacuum thermoforming, foaming, coating, heat sealing and welding. Film products include packaging film, heat shrinkable film, agricultural film, food packaging film, laminated film, etc. Industrial use includes household appliance accessories, window sealing materials, wire insulation sheathing, etc. Daily necessities include toys, cushions, container covers, etc. Auto parts include shock absorbers, fenders and decorative accessories. It can be modified by blending EVA resin into LDPE and HDPE in a certain proportion.