Ester, Ether, and the Different Varieties of Polyurethane Foam

Polyurethane foam is a widely used material because of its versatility and its ability to be customized. No matter the application, there is likely a type of polyurethane foam that can fit well, you just need to know which type of foam to use. 

These are the primary differences between the different varieties of polyurethane foam. 

Open Cell Polyurethanes vs. Closed Cell Polyurethanes

Polyurethane foam types are generally broken down into two categories: open cell and closed cell. The difference in the foam types is the cell structure. Open cell foams have a cell structure that is “open,” meaning there is substantial space between the cells of the foam. This creates a less dense piece of foam that allows air and moisture to pass through. This makes the foam ideal for filtration applications and those exposed to water and moisture, like marine foam applications. 

Blowing agents are used to fill the space between the cells of closed cell foam, forming an effective barrier against air and water. This makes these types of foam denser and better able to stop liquids and air from passing through. They are often used in gasketing applications or those that require a more supportive piece of foam that can withstand heavier objects. 

Ester vs Ether Polyurethane Foams

Ester and ether urethanes are two of the most commonly used types of urethane foams across most industries and applications. They are similar—both being urethane polymers—but small differences in their additives create two distinct types of polyurethane foam that are ideal for different applications. 

The primary difference between ester and ether polyurethane foam are their bases—ester-based polyurethane has a base of polyester; ether-based polyurethane has a base of polyether triol. These bases are combined with different additives, resulting in chemical reactions that create unique properties for each type of urethane. 

Ester-Based Polyurethane Foam

Ester-based polyurethane foam is a slightly more rigid urethane foam that offers greater support than its ether-based urethane counterpart. Ester polyurethane is known for its smaller cell structure (but it’s still an open cell foam), which offers more shock absorption and a slightly firmer, more secure surface. It can also be treated with anti-static agents to make it suitable for protecting electronic devices without fear of damage from electrostatic discharges. 

The foam’s largest drawback when compared to ether-based polyurethane is its weakness to moisture. Ester-based urethanes are generally susceptible to hydrolysis, so exposure to water will often break down the material. However, ester-based urethanes are resistant to chemical solvents. 

Use ester-based polyurethane foams if you need foam that is: 

  • High tensile and tear strength 
  • Chemical and solvent resistance 
  • Higher rigidity and support 
  • Good rebound 
  • Good temperature resistance 

Ether-Based Polyurethane Foam 

Ether-based polyurethane foams are less dense, more flexible, and allow for greater airflow due to a larger cell structure. Because of this, they are often more commonly used in environments where there is a lot of moisture and humidity. They are also ideal for protecting products that are more delicate and susceptible to abrasion. 

Despite its many benefits, ether polyurethanes can be less rigid than ester polyurethanes. They are also less resistant to chemicals, fuels, and other solvents. 

Use ether-based polyurethane if you need foam that is: 

  • Softer and less abrasive 
  • Light and supportive 
  • Heavily resistant to moisture and humidity 
  • Less likely to grow mold and cultivate bacteria 
  • Resistance to UV light 
  • Does not build up heat 
  • Not susceptible to hydrolysis 
  • Shock and tear resistance 


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