What Materials are Used in Injection Moulding, and how to Select the Right ones for Your Project

Material choice is one of the critical steps in injection moulding. You may know the part design, but choosing the right plastic is another concern. If it’s too rigid, the part will crack under stress. Too soft, and it won’t hold its shape. Cost always adds another layer of pressure.

The way around this is not guesswork. It’s about comparing how each plastic behaves in real-time conditions. ABS, polypropylene, nylon, or PC; each material has unique strengths and challenges. Matching those properties to your project keeps production smooth and ensures consistent parts.

This is where Mulan Group steps in. We don’t just mould parts, we help you choose the right material from the start. With 18+ years in custom plastics, our engineers know the pitfalls and the shortcuts.

In this article, we’ll look at common plastics for injection moulding, what to consider when choosing, and how our team supports you through the decision.

Why Material Selection Matters in Injection Moulding

The plastic material shapes the outcome of your injection moulding project. For example, using a brittle resin for a bearing is likely to fail. Using an expensive resin when a basic one is enough will waste money. That is why it is never just a matter of material choice, just due to availability.

You must consider the part application. An interior panel of a car should be UV-resistant, hence polypropylene can be an ideal choice. A food container requires FDA-approved plastics, which usually are polyethylene or polypropylene. A medical housing can need a mixture of ABS and non-flammable additives. Every industry has its own regulations, and the decision taken the wrong way will lead to rejection or redesign.

Some plastics fill thin walls with ease and reducing the cycle times. Others require more heat and must be carefully designed in mould so that defects like warpage or voids are not formed. As an illustration, nylon takes in moisture; hence, it has to be dried before moulding.

Lower-cost resins can pass short-term tests but are likely to be damaged in long-term use. Buying the right material may cost slightly more, but it saves money on maintenance, warranty claims, and downtime, especially in large-scale production.

Common Materials for Injection Moulding

The choice of material depends on its processing behaviour, mechanical strength, and applications. Each polymers respond differently inside the moulds, and it's important to understand these behaviors. Here are the most common materials used in injection moulding.

Polypropylene (PP)

Polypropylene is a versatile material used in injection molding. It provides a good flow and supports high-volume production at a reasonable cost. However, it may shrink when overheated. It is a flexible and chemically resistant material and is mostly find its use in containers and living hinges.

Acrylonitrile Butadiene Styrene (ABS)

ABS is tough yet has a good surface finish. It is easy to mould and retains its original colour, which is useful in consumer products. Moreover, it is dimensionally stable and applies in enclosures and automotive components. Besides this, it has moderate heat resistance. This indicates that it is not a good option for extreme conditions.

Polycarbonate (PC)

Polycrylonate is highly durable and impact-resistant. It requires moulding at high temperatures and close supervision to prevent stress marks. Its use is common in lenses and transparent housing due to its optical clarity. Additionally, it is not easy to crack, but it may be quite expensive compared to other materials.

Polyethylene PE(HDPE and LDPE)

Polyethylene is mouldable and offers elasticity. It comes in two forms. HDPE is rigid, whereas LDPE is soft to squeeze products. Its shrinkage is higher than certain materials, hence mould design should be done carefully. On the application side, it is used in packaging, toy making.

Nylon (PA)

Nylon features high wear resistance and strength. It takes up moisture, and this interferes with dimensional accuracy. Its good flow characteristics make it useful for gears, bearings, and mechanical parts.

Polyethylene Terephthalate (PET)

PET is renowned for being clear and rigid. It must be dried under controlled conditions to prevent moulding defects. It is used in bottles and transparent housings as it cools quickly and gives lower warpage. In addition, it's a recycled material.

Polymethyl Methacrylate (PMMA)

PMMA or acrylic provides high clarity and a uniform surface finish. It is easy to mould, but can be careful easily. It is also resistant to UV and used in lighting covers and outdoor components. It is cheaper than a PC. Its strength is comparatively less.

Polyoxymethylene (POM)

POM or acetal is highly rigid and frictional. It is easy to mold. It is common on gears, clips, and technical mechanisms. It can be expected to shrink, and this makes it easier to design the tool.

High-density polyethylene (HDPE)

TPE provides mixed properties of rubber and can be moulded using thermoplastics. It weighs heavily and requires equal cooling to avoid warping. It is used on seals, grips, and overmould on harder plastics.

Table Summary

How to Select the Right Ones for Your Project

To choose the right material, match it to how the part works, where it will be used, and how it will be made. Here are the common considerations before making a choice.

Strength of the Part

Not every plastic part needs exceptional strength. A thin cover or cap doesn't have the same duty as a gear or snap that endures high force. Get the strength right first; the part will crack before its time if its material is too weak.  

Consider the Operating Environment

Look at the intended part application. Heat, sunlight, or moisture can gradually break the plastic down. A part kept indoors will usually outlast the same part outdoors. So, consider the actual condition to guard product/parts against warping, cracks, and color fading issues.  

Material Behavior During Moulding

Plastic behaves differently inside the mould. Some materials can race through a thin wall, while others get blocked, leaving gaps and depressed areas to finish later. Therefore, get the melt and flow right to avoid lost mould time and expensive rework later.  

Surface Finish and Appearance

Each plastic reacts to polishing, tinting, and finishing in its own way. Choosing the wrong material can lead to dull, foggy, or extra-rough surfaces, even when the main job is done right.

Choose the Best Injection Moulding Materials with Mulan

At Mulan Group, material choice is never left to chance. We work closely with you to identify plastics that match your product’s exact performance, appearance, and cost needs. Whether your project requires tough ABS for automotive housings, medical-grade PP for healthcare devices, or impact-resistant nylon for industrial tools, we provide clear recommendations backed by years of moulding expertise.

Our in-house team tests materials under real production conditions. That means you get advice based not only on data sheets but also on proven injection moulding experience. With hundreds of successful projects across industries, we know how different plastics behave during moulding, cooling, and finishing.