The Difference Between Polyethylene and Polyurethane Foam

What’s the difference between polyurethane and polyethylene foam? While the names may appear similar, and they are both classifications of foam, the two foam materials have little in common. Understanding the differences between polyurethane and polyethylene foam is crucial when choosing a foam material—whether for a product component or for packaging. 

These are the basic details of two of the most common classifications of foam. 

What is Polyurethane Foam?

Polyurethane foam is soft, less dense foam. It is considered open-cell, meaning that the cells that make up the actual material are not cross-linked. This means air can freely flow through them, which results in a foam that gives a lot when pressure is applied to it. Polyurethane foam has high shock absorption and flame resistance (meets UL 94 safety standards). It can also easily be cut into various shapes, etc. 

There are two major types of polyurethane foam: 

  1. Ester-based polyurethane: defined by its smaller cell structure, making it slightly more rigid, supportive, and durable. It offers more shock absorption at the cost of being very susceptible to water damage. 
  2. Ether-based polyurethane: known for its larger cell structure that allows for more airflow and moisture permeability. It has a softer surface than ester-based polyurethane. 

Polyurethane is commonly used in cushioning and many other applications. 

What is Polyethylene Foam?

Polyethylene foam is a denser closed-cell foam that is known for its firmness and resistance to hydrolysis (it will not break down when exposed to water and moisture). This is because the walls of the cells within the material are closed off, preventing air and water from flowing through them.  

Polyethylene foams (crosslinked and expanded molded polyethylene) are good choices for thermal insulation and sound dampening. These types of foams can also be laminated to protect them against heat, gas, and other harsh substances. 

Another common polyethylene foam is beaded polyethylene, a hard, low-density closed-cell foam that is flexible and easy to fabricate. This type of foam is non-abrasive, a great insulator, and doesn’t off-gas or leave odors. Beaded polyethylene foams can also be used to provide support and comfort in marine applications. 

Mixing the Two Foams

There are instances where products can use both polyurethane and polyethylene foams at the same time. A good example of this is cushioning applications. Some cushions have a bottom core made of softer polyurethane foam and an upper polyethylene foam on its top. This creates a firm surface that still has plenty of cushioning underneath it. This can be used in seating and athletics mats. 


Need help choosing a polyurethane or polyethylene foam for your application? We can help. Get in touch with the foam fabrication experts at Amcon today.