What is EVA foam?
Ethylene Vinyl Acetate, EVA foam is a polymer that combines the properties of ethylene and vinyl acetate to create a material that is both flexible, elastic, returns to shape and is resilient to impacts.
EVA is a Closed Cell Foam
What are open and closed cell foams?
Foams are made up of micro cells that look like the image below.
Open cell foam: the cells do not have faces, meaning liquids and air can enter, be absorbed and held by the open cell foam. A common example would be a kitchen sponge.
Closed cell foam: the cells have closed faces, making many closed cell foams waterproof, air tight and improved resilience to mechanical stresses.
How to identify a closed cell EVA (Ethylene-Vinyl Acetate) foam
What does it look like? EVA foam is commonly coloured, black or white. The cell size is very small and almost not visible.
How does it react to water? Is it a closed cell foam? If yes, the water will puddle or run off the foam, the water will not be absorbed by the foam but some water may ‘stick’ to the foam until dried or evaporated.
How does it react to a finger imprint? Pressing strongly with a finder the foam will strongly recover back to its original shape, there may be a very slight imprint for about 20 seconds.
EVA Foam is High Rebound
EVA foam’s most noticeable quality is its ability to rebound or recover quicker than other foams, this is beneficial to many applications but not all. This doesn’t mean that it will recover better than other foams, it will only recover more quickly.
EVA Foam for Impact Absorption
EVA Foam is commonly referred to as impact absorbing because foam is generally thought of as a softer, cushioning material. However it is important to note: EVA has the highest return, which means it quickly recovers or springs back to its original thickness after an impact, more so than any other foam, giving EVA foam a bounce or spring-back quality.
So, while EVA foam does generally cushion impacts as a foam, it is less impact absorbent and more impact reflective. A slow recovery like PE foam may be better for impact absorption applications.
Impact absorption is also relative to the force and weight of the impact, this can be matched with a higher density foam that will typically be more resilient, harder and heavier for absorbing strong impacts.
EVA Foam’s Appearance
EVA foam has a very small cell structure, at densities higher than 30Kg/M3 the cell are mostly not visible, but can look to have a very subtle texture giving the foams a matte appearance, they reflect little to no light and can be machined with crisp edges and lines in just about any shape.
Open cell foams can appear more ‘aerated’ with ‘fuzzy’ edges and can have small metallic looking specks, closed cell foams such as EVA foam do not have any of these characteristics.
Everyday Uses of EVA Foam
Its unique characteristics make it suitable for a multitude of applications, ranging from everyday consumer products to specialised industrial uses.
Is EVA foam good for soundproofing?
EVA is OK but not greatly effective for soundproofing. All foams can offer some level of sound absorption, acoustic foams can reduce reverb inside a room. But to absorb and deaden sound whilst retaining the benefits of a closed cell foam (does not absorb and attract moisture, is fire retardant and UV resistant) Stratocell Whisper foam should be used. Stratocell Whisper has a sound absorption rating of NRC 1.00 which is the highest possible rating for sound absorption.
1. Footwear Industry
One of the most common uses of EVA foam is in the footwear industry. EVA is widely used in the production of shoe soles giving the wearer an athletic spring in their step, ideal for improving athletic performance.
2. Sports and Fitness Equipment
EVA foam is extensively used in sports and fitness equipment. Its high rebound and resilience make it perfect for applications that require the foam to handle frequent impacts.
Yoga Mats: EVA foam provides a comfortable and non-slip surface for yoga practitioners.
Gym Mats: Used in gymnasiums and fitness centres for floor exercises and equipment padding. It’s also a closed cell foam which means its waterproof and washable.
Protective Gear: Helmets, knee pads, elbow pads, and other protective gear often incorporate EVA foam for its shock-absorbing properties, although PE Foam should be considered and it does not have a bounce or recovery quality. It’s also a closed cell foam which means it’s waterproof and washable, does not absorb sweat or water.
Sprung Floors: EVA foam is used under sprung floors in dance studios and gymnasiums to provide cushioning and reduce the risk of injury, but also increase the athletic ability and bounce of the gymnasts.
3. Packaging and Cushioning
EVA foam is used for packaging and cushioning, but should it be? Foam packaging specialists such as Ethafoam and Plastazote studies and testing of foam cushioning for packaging show that PE, XPE or EPE foams protect fragile items from drops and vibrations during postage and shipping. EVA Foam has too much bounce, that could increase the G-forces or movement experienced by the packaged item.
4. Automotive Industry
The automotive industry utilises EVA foam for various applications due to its durability and cushioning properties. It is used in:
Car Interiors: EVA foam is used in car seats, headrests, and armrests to provide comfort and support. The elasticity and its ability to hold its shape become benefits in this application.
It’s also a closed cell foam which means its waterproof and washable, does not absorb liquids, sweat or water.
Seals and Gaskets: EVA foam is used to create seals and gaskets that prevent air and water leakage, EVA has the best elongation strength, while PE foam has higher compressive strength. So, product designs that require flexibility should consider EVA foam, while more mechanical designs that may experience higher torque from a bolt or screw should consider PE foams.
5. Marine and Water Sports
EVA foam’s waterproof properties make it ideal for marine and water sports applications. It is used in:
Boat Decking: EVA foam provides a non-slip surface for boat decks. This is because of the EVA foam’s recovery, meaning the foam is constantly trying to return to its original shape, giving a bouncy feel, the foam is pushing against the foot in this example. It’s also a closed cell foam which means it’s waterproof for all marine and water sport applications.
Flotation Devices: Life jackets, buoys, and other flotation devices often incorporate EVA foam for buoyancy.
Water Sports Equipment: Surfboards, paddleboards, and other water sports equipment use EVA foam for waterproof, long lasting padding and grip.
6. Creative and DIY Projects
EVA foam is popular among hobbyists and DIY enthusiasts for its ease of use and versatility. It is used in:
Crafting: EVA foam sheets are used in various crafting projects, from costumes to decorations.
Model Making: The foam is used to create models and prototypes due to its lightweight and easy-to-cut properties.
Custom Padding: DIY enthusiasts use EVA foam to create custom padding for various applications, such as camera cases and toolboxes.
