All Plastics Are Not Created Equal

A Look at the Top Materials Used in Plastic Injection Molding

You’ve made the decision to use plastic injection molding for your parts or to gradually switch over to plastic from metal in your parts manufacturing. Congratulations! We know you will be satisfied with the quality and savings you will experience as a result of this decision.

As a next step, you need to select the right resin material for your products. Did you know that there are about 85,000 types of injection molding plastic materials? And to make things even more complicated they have long-sounding names and lots of similar acronyms to identity them.

Don’t worry; you don’t need a degree in chemistry to choose the right plastic material. You just need to know some basic information about your application and the categories for plastic injection molding materials.

When selecting a plastic, the first thing to consider is the part’s function and physical environment. Some parts need to be thick and rigid, while others need to be thin and flexible.

For example, you’ll need to consider temperature changes, chemical exposure, moisture, and UV light. Additionally, the material’s strength, flexibility, durability, and appearance come into play. Some materials need to have the food-safe distinction.

As you can see all plastics are not created equal. To help you narrow down your selection, here is an overview of the top materials used in plastic injection molding.


Polymethyl methacrylate (PMMA), commonly known as acrylic, is a hard, clear, moldable plastic that is used in everything from automotive parts to eyewear lenses and false fingernails. Also known as Plexiglas, acrylic can be translucent, opaque, or colorized.

Some of the advantages of using acrylic plastic include:

  • Transparency
  • Weather resistance
  • Chemical resistance
  • Strength and rigidity
  • Stability


Acrylonitrile Butadiene Styrene (ABS) plastic can be used in a wide temperature range, offering high stability and insulation. ABS is used in electronics, tools, home repair equipment, and some plastic toys (such as Legos.)

Some of the advantages of ABS are:

  • Impact resistance
  • Chemical resistance
  • Dimensional stability
  • Temperature resiliency
  • Machinability


High-Density Polyethylene (HDPE) plastic is a heat-resistant food grade plastic. It is used in kitchenware, food storage containers, and refrigerator shelving. It also is used in the manufacture of containers for shampoo, household cleaning products, and laundry detergent.

The advantages of using HDPE include:

  • Made of 100% recyclable material
  • Chemical resistance
  • Heat resistance
  • Food safety


Nylon (Polyamide or PA) is used in a wide range of plastic injection molded parts, including bushings, gears, and bearings.  It also is often used in the manufacture of rope, automotive parts, and clothing. Nylon does absorb water, so it is not the right choice for marine applications.

Advantages of nylon include:

  • Low friction
  • Chemical resistance
  • Low abrasion
  • Adaptable to combinations with other plastic materials


Polycarbonate (PC) is a transparent material that has a high resistance to impact. It’s often used in eyewear, windows, sports equipment, and windows.

Advantages of using polycarbonate in plastic injection molding are:

  • Impact resistance
  • UV light resistance
  • Chemical resistance
  • Transparency
  • Rigidity


Polyetherimide (PEI) is commonly used in electronics, medical equipment, and industrial parts. Known by the trade name “Ultem,” PEI has a very high heat resistance.

Advantages of using polyetherimide include:

  • Rigidity
  • Heat resistance
  • High tensile strength
  • Flame resistance


Polyoxymethylene (POM) is a rigid polymer that has a smooth, glossy surface. Known by the name “Acetal,” this plastic is found in automotive parts, household appliances, and electronics.

Advantages of polyoxymethylene are:

  • Rigidity
  • Impact Resistance
  • Corrosion and solvent resistance
  • Smooth, reflective properties


Polypropylene (PP) is used in food-related plastic products, such as water bottles, kitchenware, plates, and storage containers. This type of glossy plastic also is used in the manufacture of toys, luggage containers, and external car parts.

Advantages of polypropylene include:

  • Chemical resistance
  • Insulation properties
  • Elasticity


Polystyrene (PS) has bending and flexing properties that make it useful in the manufacture of disposable food containers and bottles. It’s also used to make laminate floor sheeting and rigid foam insulation.

Advantages of using polystyrene include:

  • Transparency
  • Food safety
  • Stability

Thermoplastic Polyurethane

Thermoplastic Polyurethane (TPU) has high tensile and tear strength. It is used in various applications that require elasticity, including footwear, wires and cables, film and sheeting, and adhesives.

Advantages of Thermoplastic Polyurethane are:

  • Elasticity
  • Versatility
  • Impact resistant
  • Weather resistant

Thermoplastic Rubber

Thermoplastic Rubber (TPR) is a resin that is a mixture of plastic and rubber. Because of its strength and chemical and weather resistance, TPR is often used in fluid dispensers, hoses, cables, and catheters.

Advantages of Thermoplastic Rubber are:

  • Recyclable
  • Impact resistant
  • Chemical resistant

We hope this overview has given you an idea of the range of choices you have when selecting the plastic resin for your manufacturing job. As you can see, the right choice depends on your product and your unique circumstances.

At ASPM, we will be glad to assist you in making your decision. Just let us know how we can be of help? We offer complete support from product design and feasibility, through routine injection mold maintenance and repair. Our highly trained staff is prepared to handle plastic projects with varying complexity in our robust 24-hour facility. Contact us today to discuss your next project.