Is Polyurethane Rubber or Plastic?

is polyurethane rubber or plastic

While there has been some confusion on the matter, polyurethane is neither rubber nor plastic. It often looks and feels like either material, which is why people often ask for polyurethane rubber or plastic. It also has properties that make it behave like a strong, rigid plastic with the elasticity of a rubber.

Polyurethane is strong and more durable than natural rubbers or thermoplastics, and it outperforms in highly abusive environments. It is a more cost-effective material in the long run for its long-lasting capabilities. The material is cast as a liquid, so production prices are lower than heat and pressure-molded materials. Being a liquid at the start also allows it to bond well to other materials when needed.

What is Urethane?

It is categorized as a polymer used to produce materials that behave like plastics and rubbers. Polymers are made of long, repeating chains of monomers. These highly cross-linked structures produce a thermosetting material. Thermoset polyurethanes, once hardened, cannot be melted or reformed.

While one polyurethane may look and feel different from another, they all essentially have the same chemistry. The material is made by mixing two or more liquid chemicals to produce a reaction. In this case, it is the reaction of a monomer and an isocyanate. Urethane has to be an isocyanate reaction with an alcohol functional group (OH). The choice of iso and monomer is how the properties of the material can be altered. Using different compounds is also how polyurethane is able to imitate other materials. Its range of durability, flexibility, and resilience make it highly valued across industries.

The material first became a replacement for rubber during WWII. Since then, many industries have preferred to use it in place of wood, metal, thermoplastic, and rubber. It offers many advantages and embodies aspects of each material. Based on its chemical structure, it can be a coating, adhesive, foam, or molding and casting material, making it versatile for a wide range of applications.

Benefits Compared to Rubber

There are two distinct types of rubbers: natural, harvested from the latex of rubber plants, and synthetic, made of petroleum byproducts. They are classified as elastomers as they are moldable and flexible, like polyurethane. There are several advantages to using urethane over rubber:

  •  It has notable resistance to abrasion, impact, and scratches. It’s best used when a material needs plenty of strength and resilience to endure continual stress and stretching.
  • While rubber is cheaper, polyurethane has more affordable tooling costs as it is easier to produce complex parts. It’s also more cost-effective in the long term since it is made to outlast rubber.
  • It excels at resisting cuts and tears better than rubber. It also has great load-bearing capacity to handle more weight without breaking, resulting in longer product life.
  • No matter the hardness range, it maintains its properties, whereas rubbers will have limited properties. It also maintains its properties over a wide range of temperatures and other conditions. Whether hot or cold, it stays flexible and functional. Rubber will typically become brittle and lose its elasticity over time due to these stresses.
  • It can be used for a handful of applications, as different formulas offer a broad range of properties, durometers, and colors, whereas rubber is more limited.

Benefits Compared to Thermoplastic

Thermoplastics have chain-like polymer molecules and can be made of various chemical compositions. Standard thermoplastics include polyethylene, PVC, nylon, and ABS. There are several reasons polyurethane would be used in place of these materials:

  • It is an ideal material for products that are subject to high impact or sudden forces and shocks. Thermoplastic is unable to handle repetitive impact, and it is more likely to break, abrade, or degrade.
  • It outperforms thermoplastic because of its durability, abrasion resistance, and wear resistance. This makes it a suitable material for applications that experience constant friction.
  • It maintains its strength, even at higher hardnesses. Thermoplastics are more limited in their durometers and properties, which makes them crack and break under heavy loads and stress.
  • You have more freedom in your production process when using the material, especially when making complex shapes. Thermoplastics are usually heated and injected into a mold, while polyurethane can be cast or reaction injection molded at both room and high temperatures.

Benefits Compared to Metal

Polyurethane has often been used in place of metal for its unique properties and advantages such as:

  • It has better shock absorption and noise reduction abilities. This is important for applications where a quieter environment is required.
  • It is a lightweight material, which is an advantage for applications where reducing the weight of parts is essential. Its lower weight also makes it easier to work with and handle.
  • It’s the preferred material when exposure to moisture or chemicals is possible. It can handle abrasive and corrosive environments, so you get more life out of your parts. Metal may rapidly break down when exposed to certain chemicals and moisture, making the life of parts much shorter.
  • It offers reduced tooling costs, as it is typically less expensive to machine, cast, and mold into complex shapes. This allows for custom designs that are difficult to achieve with metal. There’s also no need for expensive welding or machining processes, as it cures at room temperature.
  • Metal does not have the ability to flex under stress, but urethane can be compressed and still rebound to its original shape and size.

VFI Polyurethane Materials

VFI is experienced in the manufacture of various polyurethane products. We offer coatings, foams, rubbers, and plastics for a vast number of markets. Depending on the material, they can be sprayed, injected, or poured and customized to your specifications. There’s no limit to what they can be used for, as they are very versatile and adaptable. If you need help finding a solution for your project, VFI is happy to help. Contact us today for assistance with your urethane needs.