eva foam injection molding

The Importance Of Having Shoes With EVA Midsoles

midsole

As you can read in almost all of the reviews here, most of the shoes have the famous EVA midsole. Whether we speak of running shoes, hiking boots, or sandals even, EVA is constantly on the list.

The midsole is that part of the shoe (sandwiched between the upper and the outsole) that provides cushioning and rebound, and it helps protect the foot from feeling hard or sharp objects. If it is well made, it will follow the foot line.

Midsoles provide stability against your foot, and in that order it has to be made of material that will endure all challenges – terrain, human’s weight, all possible pressure that happens during walking or running.

So what exactly is EVA and what does it stands for?

EVA stands for ethel vinyl acetate which is a man-made material that is considered foam. This is a co-polymer of ethylene (C2H4) and vinyl acetate (CH3CO2CHCH2).

Precisely, it is a polymer that has wide use.  While EVA foam is highly useful for footwear, it can be used for other things as well, like suits of battle armor.  Have a look at this video to see how versatile EVA foam can be, generally speaking:

Northside Women's Snohomish Waterproof Hiking Boot

When it comes to making footwear, there are lots of companies that are using the expanded foam rubber version forms of polymer known as EVA. Like most rubbers, EVA is soft and flexible, but also is easier for processing and manipulation in manufacturing of versatile things (midsoles included) due to its thermoplastic properties.

What makes EVA a good choice for shoes (running or anything that will flex during walking) is the “low-temperature” toughness, stress-crack resistance, waterproof properties, and resistance to UV-radiation.”

EVA is considered to be more eco-friendly, because it doesn’t use chlorine in its production, which means there is less toxicity released during degradation. Some companies prefer using EVA as a binding agent for other eco-friendly shoe materials like jute, bamboo, cork etc.

This way, the materials are incorporated with EVA to create a shoe that will function well, and will not harm the eco system when it is no longer in use.

How is it made?

To that question, here is a quick video that will give you an up close and personal look at EVA foam molding process:

eva foam

EVA materials are made of thousands of tiny bubbles joined together that hold air. Once they are compressed, they provide cushioning, and shock absorption (as you have read, most of the reviewers claim that wearing shoes with EVA midsoles, feel as if they are walking on clouds). That compression makes EVA an ideal material for performance footwear.

What makes EVA different and better than other midsoles, (in most cases polyurethane ones) is its lightness. EVA has a low density, and has low weight, so it is ideal for certain types of footwear where weight is a factor (you can’t put extremely heavy midsoles in summer shoes for instance). Those previously mentioned tiny bubbles are “forcing” the cushioning to lose some of the air, and become compressed.

Of course, EVA is not made to last forever, because with time (and constant use) any footwear product made from EVA will lose its cushioning and support.

eva foam injection molding

Among our shoe reviews, there are plenty of quality shoe brands. You have probably seen at least two of the names such as Keen and Teva.  These companies are constantly producing shoes with EVA molded midsoles.

Keen uses compression molded EVA midsoles, and foot beds to provide their customers with maximum support and protection, no matter what type of shoe it is  – sandals, sneakers or hiking boots.

 Teva, as well, uses EVA compressed midsoles, to create footwear for active people who need a highly shock absorbent heel, more than anyone else.

The one thing that works against EVA, is its short life.  Over time EVA tends to compress; users (runners especially) say that they feel their shoes go flat after a while. But this doesn’t stop world famous shoe brands from producing shoes with EVA midsoles; the majority of good running shoes have compression molded EVA midsoles (Nike and Adidas use them too). This usual problem is often “fixed” by compressing EVA in a pressurized mold, where the midsole forms a thick skin. This way EVA midsoles are made to last longer.

The best way to avoid this flattening of the EVA midsole, is to replace your shoes (especially your running shoes) every 3 to 6 months.

Thanks for reading!

About the Author davetimberwolf