Unravelling Polymers

The Definitive Blog on Polymers by Poly Fluoro Ltd.

Mapping the PTFE Price Increase

While much has been said about the causes and implications of the PTFE price escalation, we felt it necessary to go through our archives and chart out the exact extent to which the prices have changed.

The chart below shows the price per Kg in US$ for three standard grades – Virgin PTFE, Glass Filled PTFE (15%) and Bronze Filled PTFE (40%). In addition, we have included a table showing the total and monthly growth in prices.

Needless to day, the growth has been unprecedented. In Virgin PTFE, a nearly 8% increase in prices every month has put the industry in a state where there is no breathing time between processors getting new pricing information and passing on that information to the customers.

Most processors are well aware of the effect this has had on their businesses. The main issue has been convincing customers regarding the price increase and furthermore making them aware that the trend may be expected to continue. In addition to this, there is the impact on repeat business, as clients withhold contracts which would have otherwise spanned their requirements over a full year – since processors are unable to commit to prices for more than a one month horizon.

PTFE pricing revisited ? inevitabilities in long term supply and demand

When we started this blog, our aim was two-fold:

1. To inform and educate readers about PTFE, it’s applications and derived products
2. To serve as a platform for clients and other end-users to understand PTFE better and make informed decisions regarding their applications

However, it seems to have been the articles on pricing which have brought most of our traffic as regardless of how important the applications of PTFE are, it is – understandably – on pricing that most questions currently centre.

We therefore want to look at pricing again, just to see if any new information gleaned over the past couple of months helps us understand the situation any better than we did earlier.

Since our last blog on the impact of Fluorspar on PTFE prices, we have – like all other processors – been praying for stability. We haven’t been praying for a reduction in prices – that would be optimism to the point of pure irrationality. However, if prices could simply stabilize – even for a few months, it would give us some time to re-group, re-assess and possibly resume normal operations.

However, the pricing fluctuations have been coupled with lesser-known events in the background and together, these effects are causing the stabilization process to take much longer than earlier assumed.

We would like to take a look at some of the news floating in the market at present. We can vouch that since these are from rather reliable sources, we are inclined to believe them and therefore base our outlook on their implications:

1) Fluorspar shortage is no longer an issue

A supplier who regularly sources semi-finished PTFE from a Chinese manufacturer told us this anecdote: The supplier approached the manufacturer with the offer to supply R22. The proposed arrangement was that the PTFE manufacturer could then supply the resin manufacturer with R22 (assumed to be in very short supply) and in return procure resin at a discounted price. The supplier was shocked to hear that the resin manufacturer declined – saying that they had ample R22 to meet their production needs. This does lead us to believe that although the Fluorspar story may have started the PTFE price frenzy, it is now not playing as significant a part.

2) European resin manufacturers have re-allocated resources away from PTFE

This was partly confirmed by a representative from DuPont, who stated that their company was slowly coming out of PTFE resin manufacture, as long-term competition against Chinese suppliers was not feasible for them. The resulting effect, we hear, was that most of the European resin manufacturers have sub-contracted their PTFE business to Chinese resin suppliers. Since the realization for PTFE resins in Europe is much higher – the European price has become the new acting price across the global market.

This impact does throw some light on why the PTFE prices have increased so drastically all over the world. On the one hand, we have a supply constraint, as European manufacturers no longer compete in the market. At the same time, you have a huge supply-demand mismatch as European demand for resins stays the same and this drives up prices.

3) Russian suppliers are in a state of flux

From what we have heard, Russia has two main companies who manufacture PTFE resins, one of which acquired the other. The combined company is said to be undergoing some transition issues and management is also contemplating moving away from PTFE and into ETFE. The result has again been to constrain supply, impacting prices in the process.

4) Pricing set to stabilize within the next 2-3 months

Obviously, many are hoping that things will settle down sooner than this, but considering the extent of changes occurring across the market, one might expect that it would take no less than a few months to stabilise.

Our own local the supplier – who increased prices by another 30% in the month of July 2011, assured us that this would be the last-but-one, if not the last, price revision from their side. The current price we are getting is US$26.5 per Kilo for virgin PTFE resin. From what information we have from our European counterparts, it appears that local rates there are around the same price – so it does look like some sort of balance has been reached.

For those thinking about the long term implications of all this, we can infer the following from what data we have already collected:

  1. High prices are here to stay. If there is one thing that all this has shown us, it is that the demand has stayed strong enough despite the price escalation. This has justified the price hike for resin manufacturers from a business standpoint
  2. Long term, quality will improve. Although it looks like Chinese companies will be doing most of the manufacturing of PTFE resins, if they are supplying through companies like DuPont and 3M, the quality controls will most probably be more stringent.
  3. Volumes in PTFE will shrink. Although we have not seen a significant amount of substitution away from PTFE, there are murmurs of new materials and possible replacement materials in some areas. For the most part, we continue to believe that as a material, the extensive spectrum of properties offered by PTFE makes it a difficult material to shift out from. However, we do expect that at least 15-20% of the volumes in PTFE would slowly shift to other polymers such as PA66 and UHMWPE. Nonetheless, we can take comfort in the fact that a 15-20% fall in volumes when combined with a 100-200% increase in prices still implies an overall growth in the industry in value terms.
  4. Repro is here to stay. Not that anyone though that reprocessed PTFE would go away, but we do believe that the acceptance of recycled material in many applications (due to the price implications) would bring about some regularization in the market, with manufactures offering transparency on the extent to which reprocessed PTFE is used and possibly on the properties it could be expected to exhibit. Again – this would be a good thing from a quality standpoint, as buyers of semi-finished PTFE would at least know exactly what they were getting.

To conclude – we have, like most other processors, been trying to make the best out of a situation that has been completely out of our hands. We have faced a rather torrid 15-18 months, so if the end were 2-3 months away, we would look forward to that. In the mean time we would recommend planning one day at a time, because there is no telling what might happen during the next week or month.

Cantilever Load Considerations for PTFE Sliding Bearings

As a manufacturer of sliding bearings in India, one of the challenges we face is that there does not exist an official book of guidelines specifically for this type of bearing. The closest we have is the IRC:83 – which is the code book for POT-PTFE bearings, and which details the specifications of the materials to be used and also the testing parameters for POT bearings. As such the IRC:83 does provide some guidelines – but does not address the finer design requirements for sliding bearings. Consequently, during design and testing of the bearings, customers rely on the Quality Assurance Plan (QAP) we provide them, with the option to question, refute and even modify the requirements as they see fit.

 

Although the BS:5400 and AASHTO standards do make specific recommendations for PTFE sliding bearings, customers are not always willing to accept their parameters as they may sometimes vary from those specified in the IRC – in places where the codes overlap. This can result in technical stand-offs, between the customer and manufacturer, as each tries to convince the other regarding a certain process or parameter, without any official rule book, to back up their view point.

Among the more interesting technical debates we have had recently has been regarding the thickness of the top plate (upper sole plate) in bearings with high movement requirements.

Given a specified vertical load, a PTFE sliding bearing will be required to have a PTFE pad with side determined by the compressive strength of PTFE (usually taken at 100-200 Kgs per sq. cm). This side in turn determines the side of the lower sole plate. Give these two dimensions, the movement of the bearing (specified usually by the client/ contractor) will give us the side of the Stainless Steel sliding element, which in turn will give us the side of the upper sole plate.

Our designing of PTFE sliding bearings began with taking standard designs for specified loads and movements (such as C&P) and recommending them to clients. As we became better versed with PTFE sliding bearings, we started designing from scratch – using the parameters of movement, load and rotation to design customized PTFE bearings for specific project requirements. As many of the original standard drawings recommended sole plates of 12-15mm thickness for bearings up to loads of 50-65 Tonnes, we too continued with this recommendation. After all, the constraint of a bearing in taking a vertical load depends purely on the PTFE – as when compared with steel, PTFE has a much lower compressive strength (100-200 Kg per sq. cm versus steel’s 14000-15000).

It came as a surprise to us therefore when a client expressed concern over the top plate thickness – citing that the bending moment caused by the vertical load would be in excess of what the top plate could accommodate, given the overhang of the top plate over the bottom. This led us to revisit a lot of the standard designs – only to find that for similar load-movement parameters, other bearing designs did not recommend a thicker sole plate that our customer was insisting on.

We therefore went back to theory to gauge exactly how much of a bending moment would be caused by our given load and assess whether there was a case for changing our top plate design.

The formula for calculating the bending moment is as follows:

M= (P x L2)/2

Where:

P = Pressure (Kg/cm2)
L = Length of overhang (cm)
M = Maximum Bending Moment (Kg)

Once we know M, we divide by the Maximum Allowable Bending Stress (S) of the material (1650Kg/cm for steel) – to derive the thickness of the steel plate required.

In the example in question, the value of M obtained was 3941 Kgs, which when divided by S gave a thickness of 3.78cm – or 38mm.

This was a shocking revelation, as our recommendation was for 15mm – clearly insufficient for the load in question. Nonetheless, we wanted to dig deeper to find out how most standard bearing designs only called for a 12-15mm thickness – when the theory clearly showed that this was inadequate.

In most of our discussions with consultants and industry experts, the value of 38mm was ratified and we were told that this was in fact the thickness needed. They were unable to explain, however, why the standard designs did not tally with the theoretical calculations. Our question was finally answered when we spoke with a contractor who studied the drawings and design details and confirmed that while a thickness of 38mm was indeed required, the thickness of the insert plate also needed to be taken in to account.

The insert plate is installed at site and is simply a 25-30mm thick steel plate grouted/ cast along with the concrete substructure and/or superstructure. The bearing is welded or bolted to this plate and the load on the bearing is transferred through the plate as well. Thus, a bending moment will act through the layers of both the upper sole plates and the insert plates – meaning that even with a sole plate thickness of 15mm, the total thickness through which the load acts is 40mm – which is more than sufficient in our example.

We went back to our client with this, but were informed that they were not using an insert plate in this particular project and that the sole plate thickness needed to be at least 40mm as per our calculations.

The exercise was an eye-opener, because we had never before been questioned on the bending moment for sliding bearings, nor had we come across any design calculations for this in the various codebooks. However it is a critical point in the design of a PTFE sliding bearing – as there is always an overhang of top plate over the bottom. As a rule, one needs to verify that an insert plate is being used and of what thickness it is. Adding this thickness to the sole plate thickness, the designer needs to verify whether the bending moment is being accommodated. If not, the thickness of the upper sole plate must be re-worked.

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