What is EVA foam ? An ultimate guide

EVA foam is made of blended copolymers of ethylene and vinyl acetate. Vinyl acetate is usually between 10 and 40% of the weight of EVA foam. Another key material is polyethylene. Different amounts of foaming additives and catalysts affect EVA foam’s density, hardness, color, resilience, etc.

All EVA foams are closed cell foams. There are a lot of excellent features, including good water and moisture resistance, excellent cushioning and shock absorption, strong heat insulation, and long-term durability. We can find them in a lot of different places and products, such as shoe insoles, soft foam mats, foam packaging, yoga blocks, kickboards, floor underlay, custom EVA foam components, and so on.

How EVA foam sheets are made

* Preparation of plastic raw materials for EVA foam

Knowing the chemical formula beforehand can help you produce the right EVA foam quality. In the beginning, our technicians need to work very carefully on the ratio of plastic raw materials and catalysts that will be blended together.

Materials include Ethylene Vinyl Acetate Copolymer and Polyethylene, calcium carbonate, talcum powder, foaming agent AC, DCP crosslinking agent, zinc oxide foam promoter, and stearic acid lubricant.

Aside from the main elements, we also use some essential adjuvants to make our EVA foam. EVA foam is usually black or white. In order to make colorful EVA foam, color masterbatch is widely used in production. Additionally, fire retardant additives are added to EVA foam sheet to enhance heat and fire resistance. Additionally, for anti-static EVA foam packaging of precious electronic devices, we can use anti-static agents.
We can move on to the next step once all the chemical raw materials are checked and ready.

* Banbury Mixer Processing

Once we’ve got the right ratio of plastic raw materials and additives, our production operator will put them in our Banbury mixer. The internal mixer has a fully and well-sealed container with enough capacity to keep a lot of raw material. Moreover, it works highly efficiently and is great for mass production.

Heat and pressure inside the Banbury mixer will blend the previously prepared material. When it comes to actual operation, our techs will need to set the right heating temperature and pressure. After a certain period of time, the raw materials can be processed by our employee.

Here’s how the semi-finished product looks after the first working flow. EVA raw materials are mixed with other plastic materials and catalysts. Originally solid, they turn into paste and sticky under high pressure.

* EVA Material Sheet Processed by Extruder and Conveyor

The factory operator will handle the mashed plastic blend into the extruder when it’s ready. Our technicians need to adjust the speed of the sheet extruder before starting it up. Also, they’ll make sure the extruded EVA foam sheets are the right thickness for foaming.

After it’s put in the extruder, the mashed plastic blend will be squeezed by high pressure generated by the machine. It’s important to know that the mashed bend will go through metal rollers so they’ll become flat sheets. Before anything could start, the conveyor’s metal rollers were set up at an appropriate speed. After this process, we’ll get EVA sheets, not foam. Plastic sheets of high density and ready for the last but most important part – foaming.

* Foaming Process by EVA Mold Foaming Vulcanizing Machine

Our foaming machines work like toasters. We’ll get the foaming machine to the right temperature and pressure. EVA foam sheet density, resilience, and quality can be affected by different temperatures. The above-mentioned high density EVA sheets will be used to finish this process. Some of those sheets will get piled neatly in piles by our factory operator. After that, we’ll put the EVA sheets into the foaming mold, which is made from stainless steel and can withstand high pressure and temperature. The EVA foam materials are formed in molds, so the size of the mold determines the size of the EVA foam sheets. EVA foam sheets are usually 2 m long by 1 m wide. For long EVA roll, we have special machine to fabricate it and can make them longer and wider.

EVA sheets blended with catalysts will vulcanize inside the foaming mold. They will finally be foamed by high temperature after a period of time, and become EVA foam sheets in colors and densities you want. The EVA foam materials are thick, but they’re pretty flexible and can be fabricated to any thickness, shape, roll, etc. Below are some regular fabrications for EVA foam sheets.

EVA Foam Specifications

Size: Around 2 m long, 1 m wide, and 0.5 mm to 100 mm thick. Depending on the foaming molds the manufacturer has. Rolls of EVA foam can be up to 2m wide and 100m long.
EVA foam comes in black and white; blue, red, green, yellow are also available.
Density: 33 kg/m3 to 280 kg/m3
Hardness: 15-80 Shore C; 40-degree EVA foam is the most popular.

EVA foam materials have been classified and differentiated based on their resilience, hardness, surface, and foaming cell structure.

What are the benefits of EVA foam?

As EVA foam materials have a lot of advantages and perform well in actual applications, they’re one of the most popular foam materials. Check them out.

Cushioning

EVA foam material is a foamed plastic and rubber blend, not a hard material. In general, low and mid-density EVA foam materials are naturally elastic and flexible. EVA foam is also tougher than polyurethane foam. They have good cushioning capability at an affordable price, so they’re popular as cushioning materials. EVA foam can be found in a lot of products like knee pads, EVA foam mats, foam packaging and inserts, and even golf putting greens that people use the large EVA foam sheet as cushion underneath.

Resilience
When making EVA foam sheet, we can put rubber and other resilient additives in it. Once we use the resilient elements, we can create a highly resilient EVA foam. Sometimes customers need high-resiliency EVA foam, and it’s actually a blend of EVA and rubber foam. Products can be cushioned and made durable with EVA foam. Some foam products include EVA foam materials such as squeegee blades, foam seals, foam gaskets, seat cushions, and so on.

Insulation

EVA foam is a closed cell foam. They’re great for insulation. Closed-cell foams also do a better job at insulating than open-cell foams. When EVA foam is made, it goes through a vulcanization process that forms it with a cross-linked, closed-cell structure. Insulating capabilities of EVA foam include heat and thermal insulation. They can resist temperatures from minus 30 to 80 degrees centigrade. Besides, we can also add flame retardants and anti-static agents to enhance EVA foam’s insulation properties.

Resistance

EVA foam materials can resist heat as well as insulation. However, here we’re talking about its resistance to solvents and noise. The closed-cell foam structure of EVA foam allows it to be highly resistant to water, moisture, oil, and sound. With a closed cell structure, the foam has a smooth and flat surface, so it’s less likely to break. You can see how EVA foam performs well in some products like flooring underlay.

Buoyancy

EVA is used widely in marine products. It’s closed-cell structure makes it buoyant. They’re waterproof. Additionally, EVA foam is lightweight and portable. This makes them perfect for marine products. EVA foam is easily found in water floats, boat cushion mats, swim kickboards and even in life jackets.

Durability

Plastics are good materials for long-term use. Add natural rubber and EPDM to EVA foam to make it more resilient, durable, and long lasting. Rubber materials are durable, but they are heavy, so they are not portable and handy. In comparison to rubber materials, EVA foam is much more portable. EVA foam can actually perform better than rubber materials when it is produced with a resilient additive, and it is also durable.

Products and applications for EVA foam

We can make much more foam products than you imagined using EVA foam materials in different colors and densities and different foam fabrication techniques. Check out these EVA foam products.

EVA Shoes Insole

EVA foam is one of the most popular shoe insole materials. Up to 60% of all EVA foam goes into the shoe industry. Most EVA insoles are made by injection molding.

EVA Toy

Since EVA foam comes in different colors, it’s easy to make it eye-catching and kid-friendly. Plus, you can customize the sizes and shapes. EVA toys and crafts include EVA building blocks, EVA swords, EVA masks, foam craft sheets, etc.

EVA Foam Packaging

EVA foam materials are ideal for making foam packaging. EVA foam is naturally cushioning and resilient. They can also be made using many machines and techniques like die-cutting and CNC contouring. They’re on everything from packaging to case inserts.

Swimming Kickboard

EVA foam has good buoyancy and good underwater floatation. Alternatively, EVA foam materials can be made low density and lightweight. That makes them perfect for marine use. Kickboards are one thing made from EVA foam.

Foam Puzzle Mats

EVA foam puzzle mats are made of molded EVA foam with anti-slip texture. It is very common to use them in many places such as home flooring, basement flooring, home gyms, and martial arts studios. They’re easy to use with interlocking tabs, so people love them. Plus, foam puzzle tiles can cushion floors well.

EVA Foam Roller and Yoga Brick

EVA foam is a common material used in sports equipment. EVA foam rollers and bricks are popular yoga equipment right now. Both thermoforming and injection molding can be used to make foam rollers. On the other hand, EVA foam yoga bricks are made by custom foam cutting. There are a lot of colors to choose from.

EVA Foam Tape

EVA foam materials can be transformed into foam tapes by laminating and slitting. You can use them everywhere you need sealing and cushioning. Additionally, they’re a cheaper alternative to foam rubber tapes like Neoprene, PVC Nitrile blends and so on.

Custom EVA Foam Parts and Components

Thermoforming and lamination capabilities of foam make it possible to fabricate 3D foam parts and components. They’re better for cushioning and shock absorption. EVA foam parts can also be laminated to work well with fabric, film, and adhesive backing.