When the content of vinyl acetate in EVA is less than 20%, it can be used as a plastic. EVA has good low temperature resistance, its thermal decomposition temperature is low, about 230℃, with the increase of molecular weight, the softening point of EVA rises, the machinability and the surface gloss of plastic parts decline, but the strength increases, the impact toughness and environmental stress cracking resistance improve, EVA chemical resistance, oil resistance compared with PE (polyethylene), PVC (polyvinyl chloride) is slightly worse, and the change is more obvious with the increase of vinyl acetate content.
EVA compared to PE performance improvement, mainly elasticity, flexibility, gloss, permeability and other aspects, in addition, its resistance to environmental stress cracking has been improved, the receptivity of the filler increases, can be used to add more reinforcement filler method to avoid or reduce EVA mechanical properties than PE decline. EVA can also be modified to get new applications, and its modification can be mainly considered from two aspects: first, EVA is used as the backbone of other monomer grafting; The second is the partial alcoholysis of EVA.
The forming method of ethylene-vinyl acetate copolymer can use the forming method and equipment of general thermoplastics, and the processing temperature is 20 ~ 30℃ lower than LDPE.
Because of its elasticity, it can be made into rubber-like film products without having to go through vulcanization and other processes. The ethylene-vinyl acetate copolymer is easy to color, and the products are colorful. The lower limit of the molding temperature is to maintain a certain fluidity, and the upper limit is to prevent the thermal decomposition of the ethylene-vinyl acetate copolymer. The material temperature is generally controlled at 170 ~ 200℃.
The vacuum formed products of ethylene-vinyl acetate copolymer are smooth and transparent. The molding equipment used is similar to LPPE.
Similar to the equipment used in PE and PVC, it can be calendered, extruded, and multi-layer co-extruded composite.
When extrusion blow molding, the cooling of the material must be given special consideration, and the traction should also be lighter, otherwise the opening is poor, and the slippery agent should be added if necessary.
The expansion rate can be controlled effectively by adjusting the amount of foaming agent. The scraps can be recycled and no vulcanization is required. Ethylene-vinyl acetate copolymer foam has the characteristics of good elasticity, light weight, toughness and low shrinkage.
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