The Difference Between Extruded and Cross-linked Polyethylene Foam

Also popularly known as PE, polyethylene foam is the most common kind of plastic used across industries. While the polymerized monomers produce the same stable thermoplastic, different polymerization techniques create various types of PE foam. In effect, therefore, the properties of certain PE depend on the specific polymerization process it has been through. They can be classified into different categories and one major classification that is often used in manufacturing is the low-density PE foam. It has similar traits of basic ethylene that is very resistant to chemicals and has a semi-rigid structure being a closed-cell foam, which has varying textures.

A low-density polyethylene foam may look like urethane or polystyrene foam but can be distinguished by the process in which they are created. In general, there are two primary types of low-density PE foam: extruded low-density PE foam and cross-linked low-density PE foam. The extruded low-density PE foam is formed using halogenated hydrocarbon. Using high pressure, the PE and the foaming agent are combined and fed into a heated screw extruder. The mixture is then forced out through the die opening where atmospheric pressure causes it to expand and then cool and solidify. This process produces a solid low-density PE foam.

Conversely, the cross-linked low-density PE foam can be made either continuously or in batches. It is often regarded to be a bit restricted when it comes to producing only planks of PE foam. The chemical agent is used to mix with a solid PE, which is then subjected to an elevated temperature to achieve the needed cross-linking between the mixture. After this, the temperature is further increased to form the final polyethylene foam. This process of using a chemical cross-linking agent is done in batches while PE foam cross-linked through radiation is done in a continuous process. Lastly, compared with extruded PE foam, cross-linked foams have smaller cells, making them softer but able to provide great foaming properties for a wide variety of applications.