Innovation in Action: Exploring the Various Types of Plastic Injection Molding

May 9, 2024, 17:44 PM by The Stoner Molding Solutions Team
Knowing the tools for molding your products will help you get the most efficient and speedy results. Injection molding is one of the most common methods used to produce industrial, commercial, and consumer plastic parts and goods. This process can utilize various plastics with different results. Are you looking for rigidity and durability? Opacity or color? You have dozens of choices to make before you even begin production.
A large injection molding machine being prepared for filling


Every plastic used in injection molding has benefits and drawbacks, which you must consider long before entering production. If you are new to the molding industry or perhaps a long-time user of one material, learning more about the different options you could use can be helpful. So read on for a walkthrough of the most common types of plastic injection molding uses, and call us to learn more about how to get the most out of your new and exciting process.


Contact Us


What Is a Plastic Injection Mold?

The injection molding process involves heating the plastic materials, melting them, and forcing them into the mold at high pressure. This procedure allows the melted plastic to produce geometrically complex parts with smooth finishes. The machinery used in this process can require more maintenance and lubrication than lower-intensity molding, but the production volume can be high. It is a very flexible process capable of handling many types of plastic molding.

Plastic molding processes come in a variety of forms and methods. Matching the method to the result will help your business remain efficient while maximizing production times. Plastic injection molding is flexible, cost-effective, and used for everything from keyboard keys and electrical outlet plates to automotive parts and sports equipment.

7 Types of Plastic Injection Molding

Many types of plastic injection molding are used today, each of which has unique benefits to the results. The seven below are not an exhaustive list, but these are the most popular types of plastic injection molding used in an injection molding machine:

  • PVC (Polyvinyl Chloride)
  • PP (Polypropylene)
  • PET (Polyethylene Terephthalate)
  • PMMA (Polymethyl Methacrylate)
  • HDPE and LDPE (Polyethylene)
  • ABS (Acrylonitrile Butadiene Styrene)
  • Polystyrene

If you work regularly in industrial-scale injection-molded goods manufacturing, you are likely familiar with at least a few of these materials. Chances are good that even a layperson is familiar with materials like PVC and PET. While the injection molding process is the same throughout all of these—forcing melted plastic into a mold—the results have widely different use cases.


Contact Us


Polyvinyl Chloride (PVC)

Throughout Industrial and consumer goods, PVC is one of the most flexible and usable materials in the plastic injection molding machine and industry. PVC can be formulated to be softer or firm, giving it a wide array of applications. Additionally, the electrical insulation provided by this material adds to the everyday use cases, which include:

  • Food and beverage packaging
  • Textiles
  • Signage
  • Bottles
  • Toys

And though they are typically created through extrusion molding, PVC water pipes are an iconic example of this material. Injection molding applications also include storage containers, which benefit from the rigidity.

A close-up of polypropylene beads before melting and mold injection

Polypropylene (PP)

PP-molded goods are trendy in food and medicine packaging. This material is resistant to chemicals and acids and has a low-friction surface finish that is easy to keep hygienic. It is ideal for containing goods intended to be consumed. Your home may already have polypropylene bowls, dishes, or food containers!

The attractive shine and finish are usually the result of a heated mold injection process, which keeps the molten plastic liquid for longer as it cools in the mold. This is one of the cheaper materials for injection-molded goods, providing lower start-up costs for your business.


Contact Us


Polyethylene Terephthalate (PET)

PET is often known by its other name, the spun textile polyester. PET plastics are another typical food and beverage material known for their recyclability. Many standard containers used in takeout and mass-produced goods use this material. PET can give your product an attractive finish and high durability when used in branded goods like water bottles.

If you plan to produce goods in very high volumes, this recyclability can provide additional efficiency benefits throughout your process, such as faster release after molding. Reclaiming excess material from a damaged plastic part or other forms can improve your bottom line.

Polymethyl Methacrylate (PMMA)

PMMA is a very different form of plastic resin that is naturally transparent and highly rigid. These two facets come together throughout many of this material's uses. This material is desirable for display packaging and screens that need to hold firm while they showcase the goods inside.

But what's more, PMMA can be used for optical devices such as glasses, contact lenses, and lenses for cameras and lasers. Many medical industry products value this for the body-safe nature of the plastic. You might know PMMA by its other names: Acrylic, Perspex, and Plexiglass.


Contact Us


Polyethylene (HDPE and LDPE)

High-density polyethylene and low-density polyethylene are two different forms of the same material. They are types of plastic created from petroleum and are used throughout our lives:


  • Water and Gas Pipes
  • Bottles
  • Dispensing Pumps
  • Insulated Containers


  • Food Trays
  • Computer Components
  • Floor Tiles
  • Bags

The significant difference between these two materials is that the high-density formula offers higher strength and durability, whereas LDPE is more flexible. The drawbacks are that LDPE is more brittle, while HDPE is heavier. Because these two materials are based on the same formula, they can be used together to produce a broader range of high-quality parts with more straightforward material handling.

 A close-up of ABS injection molded parts

Acrylonitrile Butadiene Styrene (ABS)

This transparent plastic material is an excellent glass alternative. When used in injection molding, it's essential to design for uniform wall thickness for optimal transparency. This characteristic is useful for viewing the contents of frequently used materials such as:

  • Detergent Bottles
  • Beauty Supplies
  • Food Jars

Consumers desire this because it allows them to know when to resupply. This material also uses color very well, providing ample opportunity for branded goods in your mold design. Other common uses for ABS include toys and 3D printing filaments.


Delicate items are often packaged in polystyrene. This soft material has strong resistance to impact and is transparent. Polystyrene is also frequently used in single-use plastic products such as disposable cups and medical industry plastic goods such as gloves, vials, Petri dishes, and pipettes. When sterility is a must, polystyrene is an attractive and economical option.

Polystyrene is particularly useful for items with thin walls, common in medical applications. The variety of shapes, sizes, and colors of custom plastic parts in which you can use this material is attractive for more flexible and high-volume productions. With regular cleaning, you can make ample use of these molded goods.


Contact Us


Styrene Acrylonitrile (SAN)

SAN is not as common today, as ABS has primarily filled the consumer-focused roles that SAN was ideal for. However, SAN can be used in industrial situations thanks to its rigidity, durability, and transparency. Signage and advertising firms often use this for their products. Still, the thermal insulation properties of SAN also make it usable in containing heated goods like coffee jugs, plastic bottles, and flasks.

Find the Perfect Material for Your Business with Stoner Molding

We have served multiple molding industries for decades and have seen every material and process in use. When you choose from the types of plastic injection molding, you need to know that your decisions are well-informed and supported. We want to help you make the best final product possible with minimal tooling costs.

We at Stoner Molding have helped hundreds of molding businesses remain cost-effective throughout mass production. We know the need for injection molding and other molding processes, and we want to offer you our products that will enhance and smooth out the most difficult parts of your workflow. So, call us today and get the support of an industry leader!


Contact Us