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Distinguishing Between Different Types of Polyethylene Foam

November 05, 2018

Polyethylene foam is the most common type of plastic used. While the polymerized monomers create the same stable thermoplastic, different polymerization methods on the other hand produce different types of polyethylene foam. In effect, the properties of certain polyethylene depend on the specific polymerization process. They can be grouped into various categories and one common classification they share is that they are often used in manufacturing is low-density polyurethane foam. It has similar traits of a basic ethylene that is very resistant to chemicals. It has a semi-rigid structure being a closed-cell foam, which has varying textures.

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Low-density polyethylene foam may appear like urethane foam or polystyrene foam, but can be distinguished by the process in which they are formed. There are two primary types of low-density polyethylene foam: extruded low-density and cross-linked low-density.


-          Extruded Low-Density Foam: The foaming agent used to form this kind of foam is a halogenated hydrocarbon. Using high pressure, the polyethylene and foaming agent is mixed and fed into a heated screw extruder. This mixture is then forced out through the die opening where atmospheric pressure causes it to expand, then cool, and lastly solidify. This continuous process creates a solid low-density polyethylene foam.

-          Cross-Linked Low-Density Foam: This process can be done in batches or continuously as well. It is usually considered to be a bit restricted when it comes to producing only planks of polyethylene foam. The chemical agent is used to mixed with a solid polyethylene, which is then subjected to a higher temperature to achieved the needed cross-linking between the mixture. After which, 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 foam cross-linked through radiation is done in a continuous process.

While both of these low-density foams may look similar, they differ in the size of their cells. Extruded foams have bigger cells than cross-linked foams. The latter tends to be softer than the former, but overall they provide great foaming properties for a wide variety of applications. Call or email us today to learn more about our products and services.