Foam Materials: Polyethylene, Polyurethane, Polystyrene
What is foam made of? Many different foam types are made from many different materials, based on the product’s density and the process. In this article, we will introduce the most common foam materials: polyethylene, polyurethane, and polystyrene.
There are many types of foam in the world: open and closed-cell foams, cross-linked PE (polyethylene) foams, rubber foams, PVC foams, polyurethane, etc.
Our products can be found in several fields:
- Sport, Home, and Leisure
- ProGame and Tatami
- Adhesive tapes
- Business solutions
- Industrial foams
Let’s see how the most common materials are used.
Polyethylene belongs to the family of polyolefins. Trocellen produces cross-linked polyolefin foam sheets.
Polyethylene foam is based on Polyethylene, one of the most widely used plastic material in the world. It can be used in many ways, from insulation to sports equipment, from the automotive industry to packaging, even in the footwear industry.
PE foam typically shows a closed-cell structure, open-cell PE foam is very rare. The polyethylene can be crosslinked to increase material strength.
The closed-cell foam has many advantages such as light weight, durability and flexibility. It is resistant to water, moisture, and chemicals, furthermore its vibration damping and absorbing effect makes it extremely durable. PE’s thermal and sound insulation abilities are also outstanding.
It can also be molded or thermoformed to create a three-dimensional structure. For high thicknesses it can be laminated.
Closed cell cross-linked polyethylene foam (XL-PE-foam)
Cross-linked polyethylene foam is a closed-cell foam, and that makes the material more durable. The crosslinked structure can be initiated by adding chemical crosslinking agents or by treatment with accelerated electrons. Although the products materials can be made by different polyolefins, like EVA or polypropylene, it is common to name them XL-PE foams instead of naming them XL-PO foams, which would be correct. For simplification the name ‘XL-PE foam’ is used in this text, covering also other polyolefin base materials.
The XL-PE foam shows a similar resistance to water and many chemicals as its main raw material, polyethylene. The fine cells and the closed cell structure create a flexible but stable product with a pleasant feel and a very high vibration damping effect.
Chemically cross-linked XL-PE foam surfaces are quite resistant, by applied surface modifications properties like surface conductivity and increased fire resistance can be reached.
XL-PE foams are commonly used in automotive industry, architecture and mechanical engineering for thermal and sound insulation.
One of its biggest advantages is that it keeps its insulating ability even after decades: it’s resistant to weather effects and chemicals, thus even mold is not growing on it.
It is also good for expansion joints and for packaging. In addition, mattresses, and shoe soles are also made from it.
Bio-based cross-linked polyethylene foam
This foam is made almost entirely from sugar cane obtained from biomass, so the production is environmentally friendly. Sustainability is also supported by burning the remaining sugar cane, which produces additional energy.
As bio-based XL-PE foams show no other properties they can be used in the same applications than crude oil based types.
Extruded polyethylene foam
Extruded polyethylene foam is produced by using a one-step process, Gas is injected into the barrel of a special extruder, once the melt leaves the machine through the die the gas expanded the melt and a foam is formed. Extruded Polyethylene foam has a closed cell structure but is not crosslinked. It is typically used for packaging applications, as the production process is very cost effective. Extruded PE foam is environmentally friendly, recyclable also possible in very low densities. Product properties can be varied widely by changing polymer type, density, thickness and additives. It has it limits in some technical applications with special requirements concerning thermoformability, durability and tolerances.
Flexible Polyurethane Foams
Polyurethane or PU foams are broadly used, mainly for furniture cushioning, mattresses, seating and textile backing. PU foams are made by entrapping an expanding gas during the polymerization of polyfunctional alcohols and isocyanates. Product properties are mainly defined by the type of polyol being used, depending on the production process closed and open cell structures can be created.
PU foam properties are often classified by corresponding densities.
Due to its crosslinked structure PU foams are difficult to recycle. At the end of its lifetime PU foam is often cut into foam flakes which are used to form new PU-sheets.
Polystyrene (EPS and XPS)
Polystyrene foam is made of Polystyrene, the production can be starting by filling gas filled beads into a heated mold or by extrusion of Polystyrene with injecting expansion gas into nthe extruder. EPS and XPS are widely used for many applications in construction, Automotive, Packaging and other applications. type of foam. It’s advantages are clear: low cost, low density, clarity, dimensional stability, and adaptability to radiation sterilization.
As it is a quite stiff foam type it is preferred for applications which do not require high flexibility and resistance against creeping under load.
Rubber foam is not made of plastic, but from rubber, even though it’s considered as a foam. Different types of rubber foams are available:
- NBR (nitrile butadiene rubber)
- EPDM (ethylene propylene diene monomer)
- Normal caoutchouc
The most widely known for insulation purposes from these is EPDM rubber, which is closed-cell, good insulating rubber foam type. It is very soft and shows a smooth surface which makes it flexible and easy to assemble, for example as pipe insulation. EPDM rubber foam is sensitive to light, oxygen and heat, which causes deterioration. Due to this degradation indoor applications are preferrable, product status and performance should be checked from time to time.
TPE foam (Thermoplastic elastomer foam)
TPE foam covers a broad range of foam types. By combining elastomeric and thermoplastic raw materials the final product properties can be widely modified. TPE materials have been invented to substitute natural rubber, as the natural sources for rubber are limited. Special know-how is needed for the compounding of the TPE material. Typical applications are sealings and gaskets with high mechanical equirements.
Polyvinyl (PVC) foam
PVC foam can have a broad range of characteristics, based on the PVC grade used, plasticizers and other components in the recipe rigid or flexible foam types, can be generated. It is possible to create open and closed cell types. There are different production processes in place, on one side extrusion processes for creating sheets and rolls, on the other side PVC can be foamed at atmospheric pressure to form for example wall paper or artificial leather. PVC foams show very good chemical stability, good fire retardancy and weather resistance, which makes them useful for example for marine applications.
The formerly used stabilizers based on heavy metal and the release of plasticizers in toys had created a negative image for PVC based products.
About foam materials from Trocellen
Even though we are active in such diverse areas, our solutions are all based on the similar principles: excellence, permanent performance, lightweight products, environmentally friendly processes and simplicity.
Check our products based on industrial usage!