At Poly Fluoro Ltd. we started our journey with PTFE and gradually expanded into other polymers. Initially, this was at the behest of existing customers, but over time our expertise in machining plastics meant that we were comfortable offering a variety of options to our clients, rather than try and force fit PTFE into their application.
We discovered the benefits of PEEK in one such exercise. Although we have already blogged extensively on the benefits and properties of PEEK, our own experience in dealing with this material serves to explain much of the commercial and technical queries surrounding this material.

PEEK in India is a small market in terms of volumes. The total consumption is only about 35 Tonnes. Of this, most of the material is imported as semi-finished rods and sheet, with only 12-15 Tonnes being processed from resin indigenously. Small as these numbers are, keep in mind that semi-finished PEEK sells at anywhere between US$275-US$400 per Kg – so in value terms, the market is not as small as the volumes suggest. Nonetheless, it is very much a niche market – even among speciality polymers.

Being present in the PEEK market as a processor poses many challenges. Some of these are technical in nature, while others relate to the commercial issue (PEEK is very expensive) and how clients respond to PEEK. Again, we have touched on some of these points in our earlier article – but as we have delved deeper into PEEK processing, many new findings have arisen.

Compression moulding PEEK not a simple affair

There are many challenges in compression moulding PEEK and most of these do not get explicitly highlighted in manuals and guidebooks. In most manuals, the process is outlined in 5-6 basic steps, which at first glance make PEEKappear a very friendly material to deal with.

In reality, the process is time-consuming, highly sensitive to the exact process needed and very specific in the type of tooling required.

The benefit of compression moulding PEEK over, say extrusion is that we are able to make customized dimensions based on the customer drawings. The stock piece for a part measuring 70mm in diameter can be moulded as 72mm, rather than using a 75mm rod. Over a 50mm length, this saves almost 25 Grams per part – which is significant when we consider the cost per Kg. Furthermore, if the part has an internal diameter the saving is even more, as the same cannot be attained in extrusion for large diameters.

However, against this saving, the time consumed to make a 50mm part would be many times what extrusion would take. Compression moulding is known for low productivity and even a large processor is only able to consume 20-25 Kgs per day of production. In India, however, where labour is inexpensive, this is not a huge cost factor – it only limits volumes. And since PEEK is still a low volume polymer – even processing 4-5 Kgs a day can be significant.

The actual process of compression moulding PEEK is also not straightforward. The 5-6 steps mentioned in the manuals each contain nuances that need to be fine tuned until you reach a process that most suits the equipment available. In our own experience, we have found that over 25-30 trials had to be taken, each using up between 250-800 Grams of resin. After each trial, some parameters were changed before taking another trial. Parameters such as pressure, peak temperature and soak time all need to be varied to control issue such as porosity, cracking, black spots and cold spots.

In addition to this, the selection of dies is critical. PEEK, in its molten form can be a very aggressive material and we have had many steel dies get corroded during moulding. Again – finding a balance between a strong die metal and the correct process is critical in obtaining a final process that is both economical and productive and which yields a high quality final product.

Variants and substitutes do exist for the price conscious

We have had some success in blending PTFE with PEEK ratios of 5%, 10% and 15% by weight (ie: PTFE+5/10/15% PEEK). Again – the process of blending is not straightforward and the PTFE itself needs to be processed slightly differently owing to the fact that PEEK melts at a higher temperature than PTFE. However, the final blend has proven to be useful in applications involving sealing and needing high wear resistance, with a low coefficient of friction.

Another alternative to PEEK is PEK. PEK is very similar to PEEK and is processed in much the same way. As far as properties go, some have even suggested it is slightly superior on some parameters. Commercially, it is roughly half the price of PEEK – which makes it a very tempting alternative. However, PEK is still being proven in OEM applications, whereas PEEK has been around long enough to give any OEM designer confidence in its properties.

Marketing PEEK is a challenge

In a market like India – which is highly price sensitive – PEEK is a difficult product to win customers over with.

PEEK is usually the last choice of any OEM due to its price, and if someone has not come across the material before, it takes some educating before they are convinced that any polymer exists at such a price. And while PEEK is well established in the West – in India, it is still very nascent in comparison and clients do not always see the long-term benefits of using it.

Furthermore, the relatively recent introduction of PEK into India is threatening to take some of the long-term market share from PEEK, as in a price sensitive market, people may be willing to make the gamble on a cheaper substitute.

We have been receiving many mails asking us to map or at least project the PTFE price trend going forward. Since our last post on PTFE pricing was about a year ago (Feb 2012), it is a valid question to ask whether there has been any further volatility in this market and what that implies for prices as a whole.

To lay any suspense to rest right away – we can firmly say that prices have indeed been stable this past year and it is due to this stability that our own interest in analyzing the prices has dimmed somewhat. However, that is not to say that things would continue along this vein indefinitely. PTFE is a complex material and the dynamics involving its manufacture and sale are constantly in flux – meaning that the next shock may just be around the corner at any time. So we would like to look at some of the buzz surrounding the industry in a hope to at least demystify the future to some extent.

Prices are expected to remain stable throughout 2013

This is the general consensus as of now and is due to two primary factors:

1. There is a general slowdown in global demand (much in line with most other industries) that makes it risky for resin manufactures to experiment with pricing like was done early in the price escalation of 2010-11
2. There was a significant over supply of resins when prices were high and this led to huge inventories which manufacturers are still offloading

In some areas it is believed that there is still some scope for prices to fall further. However, it is most widely accepted that the current rates are stable and should be for the foreseeable future

China still a key player – but not the only price maker

Back in 2010, it was largely a price war between manufacturers that led to very low PTFE prices. Much of this was driven by China – where the abundance of fluorspar and the support from their government allowed Chinese PTFE manufacturers to scale up very quickly.

Although China remains a key player still, a few factors are affecting their economics and scale right now:

1. The government support has reduced for PTFE resin manufacturers in China. With the clamping down of R22 within China (for environmental reasons), there is a subsidy of US$0.5 per Kg of R22, which is no longer being offered by the Chinese government.  Owing to this, Chinese manufacturers have had to pass on this cost increase of about US$2 per Kg on to PTFE processors
2. Due to quality issues with Chinese resins, many OEMs have started specifying that their parts be made from resins such as DuPont, Daikin or AGC. Many semi-finished PTFE processors have also shifted away from Chinese resins due to the instability of the material. It was long believed that China reserved the good quality resin for their domestic manufacture and preferred to dump the off spec Chinese resins was upheld by the Indian government). This has hit the volumes of Chinese resin manufacturersgrades into other countries (one of the reasons why the anti-dumping duty on
3. Another key issue is repro material. While India earlier had significant imports of Chinese semi-finished PTFE materials, most of this was repro material but was being passed off as 100% pure virgin PTFE in the local market. This high intake of semi-finished PTFE was affecting the local semi-finished manufacturers as well as local resin suppliers. However – owing to the major quality issues with repro and the lack of accountability and transparency in the percentage of repro being incorporated, many companies have had to stop procuring semi-finished PTFE from China and have started buying domestically – where it is easier to monitor quality and also return material if found defective. This has led to a resurgence in domestic PTFEsemi-finished goods production and also an increased off-take from local resin manufacturers.

With China on the back foot due to the reasons listed above, it may be safe to say that price manipulation and/or competition is for the time being not a threat – since it is usually with China that most of these issue do arise. Hence, the current view is that of stability – and we should enjoy that while it lasts.

In a world of specialized plastics requiring immense tensile strength or high wear resistance or minimal coefficient of friction, Delrin holds its own against the more versatile polymers such as PEEK and PTFE.

Our own experience with Delrin began with the PTFE price increases in 2010-2011, as we scrambled to find substitutes for PTFE to offer clients, without compromising too much on properties. As we have already stated in earlier articles – finding a true substitute for PTFE was futile. However, despite our attempts to push UHMWPE and PA66 as replacements (materials we were more familiar with), it was ultimately Delrin which clients were most comfortable in adopting.

What is Delrin?

Delrin (brand name of DuPont) is also commonly referred to as POM (Polyoxymethylene), polyacetal, or simply acetal. The names all refer to a polymer that is characterized by a high tensile strength, high stiffness, low coefficient of friction and excellent dimensional stability. In addition to its properties – Delrin is a relatively inexpensive material compared to PTFE and even PA66. This makes it a sought after choice in machined component development – as the parts are dimensionally very stable and significant trials can be done without being too expensive.

Properties of Delrin

• Delrin is characterized by its high strength, hardness and rigidity to ~40 °C
• In its natural form, it is a white (opaque) plastic, although it is easily pigmented and often available in a variety of colors
• Delrin has a specific gravity of 1.410-1.420 g/cm3
• As a homopolymer it is 75-85% crystalline with a melting point of 175°C, while as a copolymer has a slightly lower melting point of 165–175°C
• It has a relatively low coefficient of friction of 0.2 – much higher than PTFE, but still suitable for a wide number of engineering applications
• Delrin is resistant to a wide variety of chemicals including alcohols, aldehydes, esters, ethers, hydrocarbons, agricultural chemicals, and many weak acids and bases. This ability is even more impressive when we consider that even under harsh chemical environments, Delrin does not lose its dimensional stability
• Electrically, Delrin rates slightly below PTFE, but is nonetheless a very useful substitute. Its dielectric constant (~3.5) is only slightly higher than PTFE (~2)

Advantages of Delrin:

• High mechanical strength and rigidity
• Toughness and high resistance to repeated impacts
• Long-term fatigue endurance
• Excellent resistance to moisture, gasoline, solvents, and many other neutral chemicals
• Excellent dimensional stability
• Good resilience and resistance to creep
• Natural lubricity
• Wide end-use temperature range
• Good electrical insulating characteristics

Due to its versatility, Delrin finds uses in a number of applications including:

• Automotives
• Industrial equipments
• Consumer goods
• Medical equipments
• Electrical equipments

Machining Delrin

As a machined item, Delrin is particularly easy to work with. With PTFE, we need to consider the softness of the material and also its sensitivity to temperatures, with nylons and UHMWPE, we need to be careful of the part melting during machining, with PEEK, the tool itself can break, if we do not control the RPM. However, Delrin is surprisingly accommodating as the part retains its stiffness, but is still soft enough that the tool is able to work through the plastic. In addition, the dimensional stability post machining is also excellent. While we have had instances of PTFE parts being under tolerance when shipped to colder climates, the same is not an issue with Delrin parts.