A Guide to Plastic Injection Moulding Material Selection

Selecting the right material for injection moulding is critical in creating high-quality, durable products. But it’s not just about performance – it’s about aligning material choices with design, manufacturing, and budget requirements. Therefore, it is always best to involve a certified and skilled injection moulder as early as possible in the process. Their expertise will often help you avoid costly material selection or design mistakes that can significantly impact project timelines and budgets.

In this guide, we address key considerations for effective plastic injection moulding material selection. From practical strategies to expert advice, you’ll gain insights that will help you make informed decisions, avoid costly mistakes, and ensure a smooth injection moulding process.

When selecting materials for injection moulding, it’s crucial to define your product requirements to ensure optimal performance and durability. Here are the main things to consider.

Begin by assessing the mechanical demands of your product in detail.

Identify the type and magnitude of loads your part or product must endure, whether static or dynamic. For instance, a stationary plastic component bearing a constant weight, such as a structural bracket, may require materials with high compressive strength, like certain grades of polyethylene. On the other hand, moving parts or components subject to vibrations, such as plastic gears or clips, demand materials with excellent fatigue resistance, such as glass-filled nylon.

Additionally, consider the level of impact resistance required for the product’s intended application. Tough materials like ABS or polycarbonate benefit applications such as protective casings. Assess whether the product will face repetitive stress or cyclic loading conditions, which require materials capable of maintaining performance over time.

Perfectly matching your chosen material’s properties to performance needs ensures increased reliability.

When selecting your material, consider the environment where your product will be used. Will it be exposed to UV light, extreme temperatures, humidity, or harsh chemicals? Evaluating these factors helps ensure that the material from which your part or product is made can perform reliably under real-world conditions.

• Temperature Considerations: Materials must withstand the operating temperature range of the application. For instance, components used in high-heat environments like automotive engines require materials with excellent thermal stability, while low-temperature applications might prioritize flexibility and impact resistance.
• Humidity and Moisture Resistance: In environments with high humidity or direct water exposure, materials resistant to moisture absorption, such as polyethylene or polypropylene, are ideal. Moisture-sensitive materials may degrade over time, impacting performance.
• UV Exposure: Exposure to UV light can degrade some plastics, leading to discoloration and brittleness. UV-resistant materials like acrylonitrile styrene acrylate (ASA) are advisable for outdoor applications.
• Chemical Exposure: If the product will be exposed to chemicals, solvents, or corrosive substances, make sure to select a chemically resistant material like polypropylene. This material offers good chemical resistance, making it suitable for such conditions.
• Indoor vs. Outdoor Use: Harsh environments demand more robust materials that can endure fluctuating conditions, whereas controlled indoor environments may permit the use of cost-effective alternatives.

Regulatory and compliance requirements are another important aspect of the plastic injection moulding material selection process. You should always consider choosing materials that meet the industry certifications required for your product.

• In medical applications, materials must comply with ISO 13485 and U.S. Food and Drug Administration (FDA) standards to ensure biocompatibility and safety. Some suitable materials are Polycarbonate, Polypropylene, Silicone, Thermoplastics, etc.
• Aerospace materials (PSS, polyimides, PEEK, etc.) often must meet AS9100D standards for durability, flammability resistance, and quality assurance.
• Materials for automotive injection moulded parts should align with ISO 9001 and IATF 16949 certifications to guarantee performance and consistency. Commonly used materials include PP, TPU, TPE, HDPE, ABS, etc.

Selecting compliant materials avoids regulatory issues and ensures industry acceptance.

Another important consideration when selecting injection moulding materials is aesthetics. Define the desired visual appearance of your product early on. What color would it be? Do you need a specific texture or finish to meet your design goals? Some materials accept pigments well, allowing for vibrant colors, while others may offer a glossy or matte finish.

Some of the suggested materials to attain the desired finish are:

• Matte Finish: Materials like polypropylene (PP) and acrylonitrile butadiene styrene (ABS) are ideal for a subtle, non-reflective look.
• Semi-Glossy Finish: Polycarbonate (PC) and high-density polyethylene (HDPE) balance sheen and subtlety.
• Glossy Finish: Polystyrene (PS) and acrylic are excellent choices for a high-shine, polished appearance.

Note: While finishes are important, plastic injection moulding material selection must also consider the functional, environmental, and regulatory factors mentioned above to ensure overall compatibility with your product’s needs.

Mould design and quality will also have a major impact on the aesthetic appeal of a part.  Generally, a lower-quality mould will not be able to sustain the finish required for consistent long-term output without costly and time-consuming polishing and tweaking.

Taking all these factors into account will help you select a material that meets both functional and aesthetic requirements, resulting in a successful injection moulding process and a high-quality product.

When selecting materials for plastic injection moulding, it’s essential to understand the options available to make informed decisions. Here are a few things to look out for.

Engineered plastics like Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), and Nylon (Polyamide) are known for their strength and durability. These materials are ideal for applications requiring enhanced mechanical properties. Choose engineered plastics when your product demands higher performance than standard plastics can provide.

Materials such as Polypropylene (PP), High-Density Polyethylene (HDPE), and Polystyrene (PS) are budget-friendly options. They are suitable for products where cost efficiency is a priority without compromising basic functionality. These materials can be used to produce high-volume, low-cost injection-moulded parts.

High-performance polymers like Polyether Ether Ketone (PEEK), Polyimides, and Polyphenylene Sulfide (PPS) offer exceptional thermal and chemical resistance. These materials are suitable for demanding applications in aerospace and medical devices. Consider these alternatives when your product must withstand extreme conditions. 

It’s also important to consider the availability of your chosen material. Selecting a material that’s hard to source can lead to production delays and increased costs.

Imagine finalizing a design only to find out the material has a two-month lead time—that would disrupt your timeline significantly.

Always verify material availability early to ensure a smooth manufacturing process.

By understanding material options, you can select the best fit for your injection moulding project, balancing performance, cost, and availability. Your plastic injection moulder can help you choose the best material options for your project.

What would planning an injection moulding project be without assessing potential costs? This step is essential to ensure alignment with your budget and production objectives.

Selecting the right material involves balancing performance requirements with cost considerations. For instance, while high-performance polymers offer exceptional properties, they come at a premium price. More affordable materials can often meet your product’s needs without compromising quality.

It’s important to mention that the choice of materials should never be at the expense of product performance and conformity. Always discuss the choices available to you with your precision plastic injection moulder to make sure they match your specifications and budget.

Another important factor in material selection is production volume. Some materials are better suited for high-volume production due to their processing characteristics and cost-effectiveness. Selecting a material that ensures consistent quality over large quantities is vital for long-term projects.

Early discussions with your moulder about production forecasts and optimal production run size (especially for lower volume production requirements) can help you choose materials that optimize performance and cost over the product’s lifecycle.

Beyond the apparent cost of materials, there may be additional costs that can have an impact on your project budget. These include

• the design of complex moulds to improve heat dissipation, for example, or requiring special processing, can increase your initial costs.
• processing conditions such as higher processing temperatures and longer cycle times can have an impact on costs.
• custom colors or special additives (e.g. UV stabilizers, flame retardants) can significantly increase costs.
• etc.

Work closely with your plastic injection moulder to select a material that will help you achieve the perfect balance between cost, performance, and quality.

Collaboration between designers, engineers, and moulders ensures project success, avoiding costly mistakes. Designers focus on aesthetics, engineers on performance, and moulders on practical production challenges.

Open communication prevents grey areas where assumptions lead to errors, like selecting materials that don’t possess the required properties. This approach ensures material compatibility with design and manufacturing processes, which saves time, reduces errors, and ensures a successful product.

Engaging in open dialogue with your moulder can clarify material choices. Don’t hesitate to ask the following questions:

• Which materials do you recommend for my product’s specific requirements?
• How do these materials perform under expected environmental conditions?
• What are the cost implications of using these materials?
• Are there any potential challenges in moulding these materials?

These questions help ensure alignment between your expectations and the moulder’s capabilities.

While moulders offer valuable insights, we recommend conducting your own research. Evaluate the suggested materials’ properties, compliance with industry standards, and suitability for your product’s application. Combining professional advice with personal due diligence enables you to make informed decisions that enhance your product’s performance and manufacturability.

Have you considered the impact that supply chain factors could have on the schedule and costs of your injection moulding project?

Material lead times can considerably impact the production of your product. To ensure smooth, reliable production, it’s important to check whether the chosen material is readily available and what the delivery times are. For example, high-performance polymers can have limited availability compared to so-called commodity plastics. Therefore, it can be useful to select alternative materials from the outset to avoid disruption caused by shortages of certain materials.

Other factors, such as global disruptions, could also make items like the location of a resin supplier a determining factor in terms of price and/or stability of supply. Choosing a resin supplier close to your plastic injection moulder can help reduce lead times and cost fluctuations associated with changing conditions such as tariff increases, currency fluctuations, and shipping constraints.

Either way, partnering with experienced moulders and proactively managing risk improves production efficiency and ensures reliability at every stage of the injection moulding process.

Effective plastic injection moulding material selection is key to delivering high-quality, durable products while staying on budget and meeting timelines. By clearly defining product requirements, evaluating material options, and proactively managing supply chain factors, you can avoid costly delays and ensure smooth production.

Collaborate closely with experienced moulders and ask the right questions to ensure compatibility. Stay proactive and flexible—these steps will help you avoid costly delays and achieve outstanding results.

PreciKam has many years of experience in precision plastic injection moulding and material selection. This includes expertise in medical plastic injection moulding and clean room injection moulding. Our experts can help you choose the best material or combination for your project. Don’t hesitate to contact us!