Injection moulding is a widely used manufacturing process that involves the creation of parts and products by injecting molten material into a metal mould. This process is ideal for producing high-volume, complex components with great precision and repeatability. Because the process involves taking the polymer into a molten state and maintaining it there until it is injected into the mould, it requires careful consideration and equipment that is capable of managing the polymer in its liquid state. Well known polymers – such as polypropylene, polyethylene, and even nylons – are relatively easy to handle in this process. Not only do they melt at relatively low temperatures (anywhere between 150-175°C) but they are also fairly easy to handle when liquid, as they do not give off any corrosive gaseous effluents. They also have very predictable melt-flows and shrinkages, meaning that a part can be quickly developed using off-the-shelf metrics that can usually be provided by the raw material suppliers.
Two materials that are less commonly used in injection moulding are PEEK and PPS. However, considering the immense advantages of these plastics, it is worth exploring how and why they are excellent candidates for injection moulding.
PEEK, which stands for polyetheretherketone, is a high-performance engineering thermoplastic that is known for its exceptional strength, stiffness, and heat resistance. It has excellent chemical resistance, which makes it ideal for use in harsh chemical environments. PEEK is often used in aerospace, automotive, and medical applications due to its high strength-to-weight ratio, biocompatibility, and resistance to wear and tear.
PPS, which stands for polyphenylene sulfide, is another high-performance engineering thermoplastic that is known for its excellent mechanical properties, high heat resistance, and chemical resistance. It is often used in automotive, electrical, and electronic applications due to its excellent electrical insulation properties and resistance to corrosion.
There are many benefits to using injection moulded parts made from PEEK and PPS, some of which include:
High strength and stiffness: PEEK and PPS are both known for their exceptional strength and stiffness. Injection moulded parts made from these materials can withstand high loads and stresses without deforming or breaking, making them ideal for use in high-stress applications.
Resistance to heat and chemicals: PEEK and PPS both have excellent resistance to heat and chemicals, making them ideal for use in harsh environments. Injection moulded parts made from these materials can withstand high temperatures and exposure to corrosive chemicals without degrading, which can increase the longevity of the parts and reduce maintenance costs.
Precision and repeatability: Injection moulding allows for the creation of highly precise parts with excellent repeatability. This means that each part will be identical to the next, which is important in applications where consistency is critical.
Lightweight: PEEK and PPS are both lightweight materials, which can reduce the overall weight of the finished product. This can be especially beneficial in applications where weight is a concern, such as aerospace or automotive applications.
Biocompatibility: PEEK is biocompatible, meaning that it is compatible with human tissue and can be used in medical applications such as implants. This makes it an excellent choice for medical device manufacturers who need to create parts that are both strong and biocompatible.
Electrical insulation: PPS is an excellent electrical insulator, which makes it ideal for use in electrical and electronic applications where insulation is critical. Injection moulded parts made from PPS can provide excellent insulation properties, which can help to protect sensitive electronic components.
Resistance to wear and tear: PEEK and PPS both have excellent resistance to wear and tear, which can increase the longevity of parts and reduce maintenance costs. Injection moulded parts made from these materials can withstand high levels of wear and tear without degrading, which can be especially beneficial in applications where the parts are exposed to abrasive materials.
Despite the benefits of the end-products, the issue with both these polymers – as well as other high-temperature plastics such as PEI, PEK, and Polyimide (PI) – is that they are not straightforward to mould. For one, the melting points are far higher than those of regular polymers, meaning that the equipment and moulds need to be able to hold the polymer at a consistent temperature in excess of 400°C. The matter is further complicated by the effluent gases generated by these polymers when in a molten state. Some of these gases can be extremely corrosive, causing damage to the regular metal barrels within which they will be held before injection. Finally, the melt flow of these polymers, while consistent, needs to be understood properly before moulding. To compound the issues, polymers such as PEEK and PPS are expensive, costing anywhere from 20X to 50X the price of regular plastics. Hence, the room for trial-and-error is limited and the equipment itself needs to be made such that wastages are minimised.
It is therefore important that injection moulding presses that are capable of handling these high-performance plastics are specially constructed. Metal housings and other components must be designed to withstand the corrosion, stress, and temperatures of the polymers in their molten state.
At Poly Fluoro, we have harnessed our existing knowhow on PEEK compression moulding and our experience with injection moulding polymers such as POM, Nylon, and polypropylene to develop a new equipment only for high-temperature polymers such as PEEK and PPS.
Overall, injection moulded parts made from PEEK and PPS offer many benefits over other materials. They are highly durable, resistant to heat and chemicals, and can be used to create highly precise parts with excellent repeatability. They are also lightweight, biocompatible, and offer excellent electrical insulation properties. There is a world of applications and we at Poly Fluoro, as always, are at the forefront.
Read More
1. PTFE Seals in Food Processing
2. Expanded PTFE (ePTFE) Gasket Tapes - Applications in Electrolysers
3. Polymer Scraper Blades - An effective, non-damaging solution to automation systems