Unravelling Polymers

The Definitive Blog on Polymers by Poly Fluoro Ltd.

PTFE in Brake Cables

The use of PTFE (Teflon) tubes extends across a variety of industries due to the exceptional properties of the material. PTFE is able to withstand high temperatures, resist corrosive chemicals, is electrically insulative, and has the lowest friction coefficient among known solid materials. PTFE tubes are made via a special process known as paste extrusion. As the manufacturing process has evolved, so too have the applications into which PTFE tubes are invaluable.

One significant application of PTFE tubes is in the manufacturing of brake cables. Brake cables are a critical component of a vehicle's braking system, and PTFE tubes play a vital role in ensuring their efficiency and durability. Around the world, PTFE is a preferred material of choice for brake cables. In India, cables with rubber cores are still largely used. However, a recent government directive has made it mandatory for PTFE brake cables for two-wheelers. The result has been a significant jump in volumes and a considerable interest in PTFE tubes.

Brake cables are a type of control cable that transmits the force from the brake pedal to the brake callipers or drums. The cable consists of a wire core and an outer casing made of metal or plastic. The wire core is responsible for transferring the force, while the outer casing provides protection and guidance. However, the friction between the wire core and the outer casing can cause significant wear and tear, resulting in reduced efficiency and increased maintenance cost. 

The typical construct of a PTFE brake cable involves a PTFE tube core, with a braided stainless steel sheath around it, and a nylon (usually PA11) outer sheath. The PTFE tubes are used as a liner inside the outer casing of the brake cable. The PTFE tube acts as a lubricant between the wire core and the outer casing, reducing the friction and wear. Moreover, the PTFE tube's low friction coefficient ensures that the brake cable operates smoothly, providing a more responsive and consistent braking performance. This feature is particularly crucial for high-performance vehicles that demand quick and precise braking.

Another significant advantage of using PTFE tubes in brake cables is their resistance to high temperatures. The brake system generates a significant amount of heat during operation, which can cause the outer casing of the cable to expand and contract. This expansion and contraction can lead to the cable's failure or reduced efficiency, resulting in brake failure. PTFE tubes can withstand high temperatures and prevent the outer casing from expanding and contracting, ensuring that the cable operates at peak efficiency even under extreme conditions.

PTFE tubes also offer excellent chemical resistance, making them ideal for use in harsh environments. Brake fluids contain various chemicals that can corrode the metal or plastic outer casing of the cable, reducing its lifespan and effectiveness. However, PTFE tubes are highly resistant to chemicals, ensuring that the brake cable remains functional and efficient for an extended period.

In addition to their functional benefits, PTFE tubes offer several advantages from a manufacturing perspective. The PTFE tubes can be extruded in long lengths, reducing the need for joints and connections, which can be a source of weakness and failure. The extruded PTFE tube can also be cut to the desired length and inserted into the outer casing, simplifying the manufacturing process and reducing production costs. The PTFE tube's flexibility also allows it to be easily formed to fit different cable configurations, making it suitable for use in a variety of vehicles and applications.

PTFE tubes in brake cables have a significant impact on vehicle safety. Brake failure is a leading cause of accidents, and the use of PTFE tubes can help prevent brake failure due to wear and tear, high temperatures, or chemical corrosion. The smooth operation and consistent performance of the brake system ensure that the driver can stop the vehicle quickly and safely, reducing the risk of accidents and injuries.

In conclusion, PTFE tubes are an essential component of high-end brake cables, providing significant benefits in terms of efficiency, durability, and safety. As safety standards become more stringent in India, it is likely that we would see an additional explosion in demand from the four-wheeler segment.

Read More

1. Graphene in Polymers - The Way of the Future

2. Injection Moulding of PEEK and PPS

3. PTFE Seals in Food Processing

Graphene in Polymers - The Way of the Future

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.

Read More

1. Injection Moulding of PEEK and PPS

2. PTFE Seals in Food Processing

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

Injection Moulding of PEEK and PPS

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

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

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