They are used in industry for the modification of elastic properties of bitumen. EVA sheets are also used to seal the whole structure in the production of photovoltaic solar panels. The cells, assembled in strings and connected in series, are sandwiched between two EVA sheets. The photovoltaic solar panel, still divided into many layers (glass + EVA + cells + EVA + back sheet), is then subjected to a thermal process under vacuum called lamination. The latter raises the temperature of EVA above 150°C for periods of about 10 minutes, enabling the polymerization of EVA and encapsulating and insulating the entire structure from air, thus ensuring longevity.
Another use is exemplified by the designer Forrest Jessee who designed and made the “Sleep Suit” with this material, able to support and protect the body in situations of discomfort.
Ethylene vinyl acetate (EVA) is a plastic copolymer of ethylene and vinyl acetate. It is used to make particularly flexible and elastic products.
EVM is formed by the copolymerization of ethylene and vinyl acetate. In principle, it consists of methylene units forming a polymer chain saturated with pendant acetate groups. The presence of a main chain that is completely saturated makes EVA a particularly stable polymer. Degradation generally occurs only at very high temperatures and very slowly.
These polymers are used like normal synthetic rubber, as adhesives or as modifiers for thermoplastic resins, in particular PVC. The main differences between various grades of EVA lie in the vinyl acetate content and polymer viscosity.
Due to the saturated structure, they cannot be attacked by ozone or UV rays. EVA has operating temperatures of up to 175°C.
This rubber is used for moulded items resistant to abrasion, ozone and fatigue.
It is used in O-rings, rubberized fabrics, sealing rings or tank gaskets of LNG carriers.
Urethane rubber can be cross-linked with peroxides, isocyanates and sulfur. Urethane rubber that features cross-linking with peroxide and sulfur is worked using techniques normally employed for other types of synthetic rubber. It can be used either without fillers and with any type of carbon black or mineral filler. It results in strong mechanical characteristics, especially in terms of tensile strength and abrasion resistance. On the other hand, it reacts poorly to heat and shows low resistance to permanent deformation at temperatures higher than room temperature. It has poor resistance to oil, since the operating temperature of the latter produces a hydrolytic effect leading to degradation. Usually this compound is integrated by anti hydrolysis additives instead of antiozonants or antioxidants. It cannot be vulcanized in steam as it results in depolymerisation.
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