Comparing Injection Urethane with Other Injection Molding Materials

Ryan Franklin
December 23, 2024

While injection urethane is a commonly used manufacturing technique, many people are unfamiliar with:

  • How it works
  • Why it is superior to traditional injection molding techniques
  • Why urethane is an ideal molding material

If you're new to the injection urethane molding process, you're in the right place. We'll walk you through the technique and help you determine which molding material is best for your unique project.

Understanding Urethane Injection Molding

Urethane injection molding is the process of injecting a liquid thermosetting plastic called urethane into a custom mold. As the liquid material cures inside the mold, it gradually hardens, taking on the exact shape of the mold.

This process requires a delicate balance of temperature and pressure. If it’s too hot, the urethane will cure too quickly, preventing the mold from filling. Too little pressure, and the urethane won’t reach all the corners of the mold.

While the process is similar to traditional plastic injection molding, urethane injection offers greater flexibility. Unlike conventional methods, urethane can take on a wide range of physical properties, from soft and flexible to tough and impact-resistant. This flexibility makes it ideal for specialized applications where other materials fall short.

Urethane Casting VS. Injection Molding

While urethane casting and injecting molding are both processes used to create parts, they are very different in application and final results.

Urethane Casting

This process involves mixing liquid resin and a hardener, then pouring them into a mold using gravity, heat, and pressure.

Casting is often the ideal choice for short-run projects with tight deadlines because it:

  • Requires less setup time
  • Has lower initial costs than injection molding
  • Allows for quick design modifications
  • Creates high-quality parts that look great

The downside of casting, however, is that it requires more labor per part. That's because each component must be mixed, poured, and taken out of the mold individually. Second, results may vary slightly between parts because each is individually mixed and poured.

Injection Molding

Unlike casting, urethane molding relies on specialized equipment to inject the liquid urethane into the mold using precise temperature and pressure. As a result, parts can be made quickly and with more consistent results. While the initial setup may be more costly than casting, the speed and accuracy with which parts can be manufactured are appealing to many of our clients.

So which method is superior? That ultimately depends on your project.

Many of our clients do not require the precision and speed of injection molding. If you have questions about methods or materials, reach out. Our team is here to guide you through the entire process, from concept design to engineering.

Types of Injection Molding Materials

While urethane is commonly used in injection molding, other materials include:

  • Polyethylene (PE) typically comes in two variations—low and high density. High-density PE is strong and rigid, while low-density PE is flexible and soft. Both are chemical-resistant and impact-resistant.
  • Polypropylene is lightweight yet sturdy, ideal for heavy and repeated use, such as automotive applications.
  • Polycarbonate (PC) is the go-to material when you need transparent components that are also impact-resistant.
  • ABS (acrylonitrile butadiene styrene) is strong, lightweight, and easy to work with, ideal for those who need to maximize cost-efficiency.

Common Urethane Injection Molding Applications

Thanks to its versatility, consistent results, and detailing, we’ve used urethane injection molding to manufacture:

  • Car bumpers
  • Engine housing
  • Shrouds
  • Ground effects

That said, the process can be used to create a wide range of products across many industries. From everyday items like appliance parts and sporting goods equipment to construction materials and industrial parts like rollers and gasket seals, urethane offers virtually endless possibilities.

Let's Create Something Extraordinary

Ready to bring your project to life? Our team can help. Whether you’re looking for a one-of-a-kind sculpture or a design for an industrial, automotive, or medical application, we have the experience and expertise to make it happen. Contact us today!