What Is Polyurethane Foam?
From your cellphone down to your shoes, thermoset polyurethane foam is virtually everywhere. Due to its flexible chemistry, this versatile material can be engineered into any shape and customized component with endless physical properties. Foam first gained its popularity in the automotive industry and is now widely used in numerous applications, including: furniture, toys, surfboards, medical devices - you name it!
But what exactly is this miracle material we keep referring to? Below is a break down how polyurethane foam is made, and the various types of foam you can use in your product design.
How Does Polyurethane Foam Work
Polyurethane foams start out no differently from a polyurethane solid. To help sum up this complex yet basic chemistry, polyurethanes are formed by the reaction of a polyol and diisocyanate. Sometimes, additives may be used to tailor physical properties of the material to meet specific design requirements. This mixture becomes foam through the introduction of gas bubbles, which, can be the result of chemical reactions or mechanical processes. To learn more about additives and how polyurethane foam can be made conductive, check out our most recent post on polyurethane conductivity.
Different Types of Foam
Mechanically blown foam is made by physically introducing air bubbles into the liquid polyurethane mixture, before curing. Think of this process similar to frothing a delicious hot cup of cappuccino milk; as the frother introduces air into the mixture, the milk will begin to foam. On the other hand, chemically blown foam employs volatile chemicals that interact with the polyurethane chemistry, generating tiny gas bubbles. This process is similar to adding baking soda into cake batter. The baking soda generates gas, thus, creating a nice and foamy cake. Both processes result in very diverse materials with a wide range of physical properties. The resulting material will display a cellular structure, which can be open or closed.
To learn if thermoset polyurethane foam is considered a safe material for consumer and environmental use, make sure to check out "Is polyurethane Foam Toxic".
The pictures above are examples of open cell and closed cell foams under a microscope. In the case of open cell foam, each of the gas bubbles are "popped" and connected to other bubbles around it. This structure creates breathable materials that will let gas and liquids through. A good example of an open cell foam is a kitchen sponge. In contrast, the gas bubbles in closed cell foams are fully contained in a wall of polyurethane, creating a non-breathable material. Closed cell foams, therefore, have a structure similar to bubble wrap. For more information on closed cell foams and the pros and cons when using this unique material, click here.
Polyurethane foam is a great tool for product design. This versatile material enables engineers to design what they envision, without compromise. From endless physical properties to customized shapes and components, polyurethane foam offers a list of benefits no other elastomer can achieve. Still curious, how polyurethane foam can improve your product's performance? Download our informative Durethane F Data Sheet, for a list of benefits, materials and formulations offered.