What Material Is EVA: Materials Matter When Buying Shoes
Many people get confused when buying the proper shoes especially athletic footwear. There are so many terms, which seem too technical to understand by a layman. One of these terms is EVA, which arguably most people are not familiar with.
But what material is EVA exactly and what is the relationship of this material with shoes, particularly rubber and running footwear? Why should buyers choose footwear using this material? Here are the basics on EVA, and its application in shoe manufacturing.
What Material Is EVA?
EVA stands for Ethylene Vinyl Acetate, which is the copolymer or the joining of two plastics in the same polymer chain, of vinyl acetate and ethylene. EVA is also more popularly known as PEVA or poly-ethylene-vinyl acetate.
EVA can produce materials that are rubber-like regarding flexibility and softness. It also has many virtues such as having excellent gloss and clarity, stress-crack resistance, UV radiation resistance, low-temperature toughness, and hot melt adhesive water properties. There are various uses of EVA in manufacturing. Often, EVA is pitted against vinyl polymer and rubber as a material for electrical applications.
Three Kinds of EVA
There are generally three kinds of EVA, and they differ in the amount of Vinyl Acetate they contain.
- Vinyl-Acetate Modified Polyethylene
The vinyl-acetate modified polyethylene is the first kind of EVA copolymer. It has a low proportion of the vinyl acetate roughly around four percent. The vinyl-acetate modified polyethylene is processed like a thermoplastics material and is usually considered as a non-toxic material.
- Ethylene-Vinyl Acetate
The second kind of EVA copolymer is the thermoplastic ethylene-vinyl acetate copolymer, which has a medium content of VA around four to 30 percent. It is a thermoplastic elastomer material, which is not vulcanized. This kind of EVA shares some of the properties of rubber.
- Ethylene-Vinyl Acetate Rubber
On the other hand, the ethylene-vinyl acetate rubber is an EVA copolymer with a high concentration of VA roughly more than 40 percent.
Application of EVA in Shoe Manufacturing
Midsoles made of EVA are the most common cushioning material in athletic shoes. EVA midsoles are found in basketball, running and most other kinds of athletic footwear. This is because the material can resist compression and is lightweight. It is also easy to form and available practically in all colors. EVA is used for cheap sneakers as well as the most expensive athletic footwear.
Why Have EVA for Midsoles?
Those who have seen the word EVA in shoes, not only ask what material is EVA but also question its importance in the footwear.
EVA is used mostly for the midsole or the sandwiched part between the outsole and upper of the footwear. The midsole is the one responsible for the rebound and cushion, which aids in protecting the foot from feeling the sharpness or hardness of an object. When well-constructed, the midsole follows the foot line.
Stability is also essential in any pair of shoes, which the midsoles provide. This is why midsoles have to be constructed from materials that are capable of handling pressure either from the weight of the user or the surface.
EVA for the Soles
Contrary to popular belief, EVA is not only used for the midsole. These days the application of EVA in shoe manufacturing is more varied than before, although there is still plenty of footwear manufacturer that uses this material only for the midsole.
EVA can also be used for the outsole and insole of shoes, not only of the athletic kind but also for slippers because of its features.
For one, EVA soles are resistant to corrosion whether caused by sea water, fats and oil, or chemicals. It is also considered safe and environment-friendly due to its anti-bacterial and non-toxic properties. It is also non-polluting.
As mentioned, EVA is great for cushioning and its anti-vibration characteristic due to its high resistance and tensile strength and toughness. This material also provides excellent insulation from cold temperature, which is why EVA is commonly used for hiking shoes.
The Downside of EVA for Shoes
Thousands of small bubbles put together that hold air is what EVA is made up of. This is the reason for its great shock absorption and cushioning qualities, making it the number one option of the athletic shoe manufacturer. However, the compression of the tiny bubbles also is the reason for the downside of using EVA for shoes.
Unfortunately, the material compresses over time. This is why most users especially runners complain that their shoes feel flat eventually. EVA material has a short life.
Manufacturers of high-end and expensive athletic footwear have found a solution to make EVA last long using molding. This process entails compressing the material using a pressurized mold so that the midsoles end up forming a thick skin, which makes the EVA soles more durable. The molding of EVA is quite expensive, which also makes the footwear made from molded EVA pricey.
What to Look for in EVA shoes?
The hardness of EVA ranges from five to 70 degrees, and buyers should look at this feature. EVA midsoles should be in the 40 to 65-degree range as lower than 40 degrees is not stable enough to protect the feet and makes the footwear prone to compression set. On the other hand, the density of beyond 65 degrees is uncomfortable.
The standard density for basketball and running shoes is roughly 55 degrees.
Shoes with EVA Material are Great
When people buy shoes, they tend to look at the design, price and, to some extent, the materials. Arguably, not every shopper is discerning and does not take the time to understand how the content of the footwear affects its comfort-ability as well as function.
EVA is a favored material by many shoe manufacturers particularly athletic footwear makers. This is because the material has many great virtues that can provide support, stability, comfort and even insulation. Contrary to popular belief, midsoles are not the only part of the shoes that are made of EVA as some product makers also choose this material for the insole and outsole.
If you want athletic footwear that lasts long, then consider buying one that uses molding process to configure the EVA. After all, the main disadvantage of this material is that it does not last long, which makes the article feel flat after some time. Luckily, shoemakers found a way to make EVA soles last longer with molding, although shoes made from this process are expensive.