The introduction of graphite into everyday life was something of a revelation. Tennis players using aluminium racquets would describe an almost superhuman feeling when they first used graphite ones. Such was the boost in strength to weight ratios that infusing graphite into any material seemed to create a whole new range of possibilities. Nearly every application – from aerospace, to automation, and of course sports, found that is revolutionised properties in a game-changing way.

Today, graphene – the upgraded version of erstwhile graphite – is being seen in much the same manner. Graphene is a two-dimensional allotrope of carbon that is composed of a single layer of carbon atoms arranged in a hexagonal lattice. It is the strongest material known to mankind and has exceptional thermal and electrical conductivity properties. The unique properties of graphene make it an excellent candidate for enhancing the performance of polymers like PTFE, PEEK, PVDF, and PPS.

Graphene-reinforced polymer composites exhibit superior properties such as high tensile strength, Young's modulus, thermal conductivity, and thermal stability. These enhanced properties make these composites suitable for use in a wider range of applications in various industries.

Polytetrafluoroethylene (PTFE) is a polymer that is widely used in the manufacturing of various industrial products due to its exceptional chemical and thermal resistance. However, its low tensile strength limits its use in applications that require high mechanical strength. The addition of graphene to PTFE can significantly enhance its mechanical properties, making it suitable for use in a wider range of applications. Graphene-reinforced PTFE composites exhibit superior mechanical properties such as high tensile strength, Young's modulus, and wear resistance.

Polyetheretherketone (PEEK) is a high-performance polymer that is widely used in the aerospace, automotive, and medical industries due to its excellent mechanical properties, thermal stability, and chemical resistance. However, virgin PEEK synergises with both carbon and graphite resulting in a high spike in material strength when the materials are mixed and then moulded. The addition of graphene to PEEK can enhance its mechanical and thermal properties even further. Graphene-reinforced PEEK composites exhibit superior thermal and mechanical properties such as high thermal conductivity, tensile strength, and Young's modulus.

Since PEEK, like graphene, is an expensive material, the introduction of graphene does not impact the cost significantly.

The addition of graphene to polymers like PTFE, PEEK, PVDF, and PPS can significantly enhance their mechanical and thermal properties to a great extent, increasing the possibilities of their applications in more demanding environments.

In addition to its mechanical and thermal properties, graphene-reinforced polymers also exhibit excellent electrical conductivity properties. Graphene’s addition to polymers like PTFE, PEEK, PVDF, and PPS can significantly enhance their anti-static properties. Graphene-reinforced composites exhibit high conductivity, low resistivity, and good electromagnetic shielding performance.

The use of graphene in polymers also has environmental benefits. The addition of graphene to polymers can make them more durable and long-lasting. This, in turn, reduces the need for frequent replacements, leading to a reduction in waste and environmental impact.

A common misconception is that graphene is prohibitively expensive and hence not viable to be used commercially. However, commercial grade graphene is presently available for about US$180-200 per Kg. While this is certainly expensive when compared with base materials, such as steel and even lower-grade polymers, there are several use cases with high-performance plastics that allow for the addition of about 5% of graphene. The subsequent enhancement in properties would more than justify the additional cost.

Today, both carbon and graphite are already used in many polymers. It remains to be seen whether the industry slowly shifts to graphene as costs of production reduce and the undeniable improvement in properties are more thoroughly understood.

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1. Injection Moulding of PEEK and PPS

2. PTFE Seals in Food Processing

3. Expanded PTFE (ePTFE) Gasket Tapes - Applications in Electrolysers

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.

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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

The properties of PTFE as a food grade material that can be machined to close tolerances is often exploited in applications where any kind of chemical contamination needs to be avoided at all costs. 

Recently, we were asked to develop a set of chevron v-seals made earlier with PTFE infused fabric, specifically to be used in the dairy industry. Our study into the existing seals being used by the client told us that the PTFE infused fabric was no longer the best option for what the client required. Fabric based components were first developed over thirty years ago and were a mainstay for many OEMs. Over time, as PTFE compounding techniques improved and the uniformity of the blend became consistent, these seals were replaced by either virgin PTFE seals or PTFE with fillers of glass, Ekonol (aromatic polyester), or even PEEK.

One of the primary reasons PTFE seals are used in the food industry is because of their resistance to chemical and biological contamination. PTFE is non-reactive to most chemicals and food ingredients, making it an ideal material for seals that come into contact with food products. Additionally, PTFE is naturally hydrophobic, which means that it repels water and other liquids, making it resistant to mould, bacteria, and other biological contaminants. This is especially important in the food industry, where contamination can lead to serious health risks for consumers.

Another important characteristic of PTFE seals is their durability and longevity. PTFE is a highly stable material that is resistant to most forms of physical and chemical degradation, including high temperatures, corrosive chemicals, and UV radiation. This makes PTFE seals ideal for use in food processing equipment that is subjected to harsh conditions, such as high-pressure washdowns, heat, or exposure to corrosive substances.

In addition to their resistance to contamination and durability, PTFE seals are also an ideal choice for the food industry because of their low friction coefficient. This means that they can easily slide against other materials without sticking or causing wear, which is important in applications where high-speed movement is required, such as in conveyor systems or packaging equipment. PTFE seals can also operate at a wide range of temperatures, from -200°C to 260°C, which makes them suitable for use in both cold storage and high-temperature cooking applications.

There are several applications in the food industry where PTFE seals are commonly used. One of the most common applications is in the sealing of rotary valves, which are used in the transfer of bulk materials such as powders, grains, and liquids. PTFE rotary seals are ideal for this application because they can withstand the abrasive and corrosive nature of these materials, while also maintaining their sealing properties over time.

PTFE seals are also used in other food processing equipment such as pumps, mixers, and blenders. These seals help to prevent the leakage of fluids or the ingress of contaminants into the equipment, which can compromise the quality and safety of the food products being processed. In addition, PTFE seals are often used in high-speed conveyor systems, where their low friction coefficient helps to minimize wear and ensure smooth movement of the food products. As a soft polymer, PTFE is unique in that it can take a tremendous amount of load (both mechanical and environmental), but that it will ultimately succumb to any major misalignment of mating metal parts. This means that in the event of failure, the seal will allow itself to be destroyed rather than damage the otherwise expensive equipment that it functions within.

The effectiveness of PTFE seals in ensuring the quality and safety of food products is unmatched. With their excellent performance characteristics and versatility, PTFE seals will continue to play an important role in the food industry for years to come.

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Read More

1. Polymers in Food Processing

2. Expanded PTFE (ePTFE) Gasket Tapes - Applications in Electrolysers

3. Polymer Scraper Blades - An effective, non-damaging solution to automation systems