Ethylene-vinyl acetate copolymer (EVA) is a type of polymer which is soft, flexible and tough. In 1930s, EVA was first invented in a laboratory located at Imperial Chemical Industries, Ltd. At that time, vinyl acetate (VA) was just doped into polyethylene to produce modified polyethylene. In 1956, compony DuPont first launched an EVA product named ElVax and after that more companies launched their products and EVA was quickly developed.^[1]

  There are four main methods are used process EVA, which are high pressure continuous bulk polymerization, medium pressure suspension polymerization, solution polymerization and emulsion polymerization. But solution polymerization and emulsion polymerization are not widely used.^[2]

  High pressure bulk polymerization is the main method to produce EVA resin. Autoclave reactor or plug flow reactor can be used as the reactor in this method and the production in different reactors is different. If the content of VA is less than 30%, plug flow reactor can be used, if content is less than 40%, the autoclave reactor is better. And the conversion per pass of two reactors is different. That of plug flow reactor is 25%~35%, but it is only 10~20% for autoclave reactor.^[2]

  Some other process methods like dielectric and microwave welding and polymer fluidized-bed coating. Dielectric and microwave welding can be applied to process the polymer whose monomers have the polar groups and for the monomers of EVA, there is eater group. Only EVA board can be produced by polymer fluidized-bed coating method, but it has its advantages.^[3]

  The manufacture of EVA varies according to its application. To manufacture memory material, EVA resin is put in the mold. Then the resin will be preheated, exhausted and went through a series of steps and finally memory material is obtained. But for 3D material and other productions, the steps of manufacture are totally different.^[4]

  The properties are almost different for different EVA products. The Young’s modulus of Shore A65 with 33% VA is 0.007–0.009 GPa, but for Shore A85 with 25% VA, the Young’s modulus is 0.02–0.03GPa. But for EVA products, the durability of water (fresh/salt) are all excellent and the durability of oils and fuels are poor.^[5]

  EVA resin also has a lot of applications for its superior properties. For example, it can be applied to adhesives and other productions for its flexibility and durability of solvent; and when processed into foam ^[6], it has high elasticity, so it can be the material of sole or packing.^[7]

[1]: History of the development of EVA. Available at: http://zz.ganji.com/zhaoshangjiameng/937103016x/ (Accessed on 19 May 2019)

[2]: Main properties and processing of EVA. Available at: http://www.doc88.com/p-1486361988702.html. (Accessed on 19 May 2019)

[3]: CES 2018 EduPack, Granta Design Limited.

[4]: Preparation and properties of EVA thermally induced shape memory polymer. Wang Libin, Wang Junhao, Wang Zhaobo. Special purpose rubber products

[5]: CES 2018 EduPack, Granta Design Limited. Flame retarded, molding and extrusion.

[6]: United Plastic Components(2019), EVA (Ethylene-vinyl Acetate), Available at: http://upcinc.com/resources/materials/EVA.html (Assessed on 19 May 2019)

[7]: Metro Foam(14 January,2019), Available at: https://www.metrofoam.com.au/eva-foam.html (Accessed on 19 May 2019)