Sintered PTFE compounds. 2

[LiamPSD]

Hello.
I was wondering if anybody is able to help me out with a dilemma.
At this time I am using compressors which have apex tips made out of PTFE with a 60% filling of bronze.
The displacer is a magnesium (8%) aluminium alloy and the housings are aluminium. We are subjecting the displacers to velocitys of 18 m/s.
We are having problems with the material shrinking and creating excessive wear on the displacer.
can anyone suggest a mix that would be more appropriate for this application.

many thanks,
Liam

 

[patprimmer]

Bronze filld nylon might do the job. We have had considerable succes with it vs PTFE in some aplications.

We can get over 75% of bronze into the nylon.

I expect it will have better dimensional stability and wear resistance at moderate temperatures, but I expect that PTFE is still better at very high temperatures, depending a bit on the mode of failure.

I am unaware of other suppliers, but maybe RTP, DSM or LNP can also supply.

Regards
pat

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[iainuts]

I've had a lot of success using Vespel CR6100 by Dupont for applications where the material sees high PV. It's a Teflon based material using long carbon fibers and put together in layers, much like plywood.

I had been using a bronze filled Teflon with Molydisulfide added as a dry lubricant, but there's no comparison. The Vespel is an order of magnitude better in wear characteristics. It's also machinable, but very expensive.

 

[LiamPSD]

HI thanks very much for the insight into the VESPEL CR6100 after doing a search for it Google came up with some very enlighting information. This seems particualrly suited to enviroment we will subject it to.
Again thanks very much for the replys. I will let you know the outcome of some further RaD,
many thanks,
Liam

 

[LiamPSD]

UPDATE:
Hi thanks for all your help on this but unfortunatly due to budget restraints we are unable to use the Dupont material.
At the moment we are considering some other materials and are trying to find alternatives to te CR6100 series.
Ian how did the molydisulfide copper filled ptfe compare to ordinary copper filled ptfe?

Liam.

 

[iainuts]

Sorry, I haven't tried it without the moly in it. Couldn't say. The bronze filled with moly goes by "Fluoralloy C" made by Saint Gobain. But honestly, the Vespel is worth the money. I know it's expensive, but penny wise and pound foolish is applicable here.

 

[patprimmer]

Unless the temperatures get very high, I would expect the bronze filled nylon to outperform bronze filled PTFE, but these things are very individual in their requirements, and wear and abrasion is a very inexact science.

MoS2 generally does not do much for improving bearing properties in plastics, other than to act as a neucleating agent. Graphite however does usually help.

Carbon fibre can be very benificial, as can aramid fibre pulp, but these can be very expensive

Regards
pat

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