Plastic material selection

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By Al Steiner | May 18, 2021
Plastic resin for injection molding

When it comes to designing a new plastic component, it’s important to realize that no material is a one-size-fits-all solution. Characteristics such as cost, temperature resistance, manufacturability, impact resistance, and structural integrity can vary widely between resins used for injection molding.

Considering all the different polymers and blends available, how do you decide which one is right for your next project? Below, we’ll be highlighting the key features of the most commonly used thermoplastics here at GMN. 

What are the most common types of plastic for injection molding?

Commodity plastics:

Commodity plastics are inexpensive plastics typically used for high-volume applications. The two most popular commodity plastics at GMN are polyethylene (PE) and polypropylene (PP). Both are very versatile resins that are buoyant, hydrophobic, and chemically resistant, making them ideal for a variety of plastic products.

While PE and PP both have decent impact resistance, they aren’t as durable as other plastic materials and are susceptible to damage from ultra-violet light exposure. The two resins are favored for cost-effective and lightweight items, such as reusable water bottles, toys, and disposable plastic packaging.

Acrylonitrile butadiene styrene:

Acrylonitrile butadiene styrene (ABS) is one of the most commonly used materials at GMN Plastics. A naturally high-sheen resin, ABS has high levels of impact resistance and strength, making it an excellent choice for bezels and housing.

ABS is also available with several additives (such as glass, colorants, or Teflon) to enhance its inherent mechanical properties. It also tends to be relatively inexpensive, making it ideal for high-volume applications that may require more durability than a commodity plastic.

Polycarbonate:

Polycarbonate (PC) is ideal for a multitude of projects due to its versatility. Polycarbonate has good electrical insulation, impact resistance, heat resistance, and fire-retardance. Polycarbonate is also naturally transparent, which means it’s a good choice when clarity is important as it can easily be matched to different colors with the addition of colorants.

While it isn’t quite as inexpensive as commodity plastics like PE and PP, polycarbonate tends to be reasonably priced. Many different grades of polycarbonate are available with varying levels of additives for additional strength, making it ideal for a wide variety of projects. 

Engineering polymers:

Engineering polymers are a family of highly engineered resins that have exceptional mechanical properties. While the exact characteristics differ, they generally have high impact resistance, stiffness, chemical resistivity, flame retardance, and heat resistance. 

Often used in highly regulated industries such as the aerospace and medical fields, the most common engineering polymers used at GMN are Ultem (polyetherimide - PEI) and Radel (polyphenylsulfone - PPSU). Polyetheretherketone (PEEK) and other materials as specified. While each of these offers a host of different benefits for plastic injection molding, given how highly specialized they are, they can be expensive and difficult to obtain.

GMN Plastics has decades of experience in not only creating custom plastic components for a wide array of projects but also incorporating them into complete assemblies to provide a holistic solution. To learn more about our injection molding capabilities, visit our website or schedule a consultation with our experts.