PPS is a high temperature thermoplastic fibre with excellent resistance to hydrolysis and so is a good complement to aramid fibres, being frequently used where their susceptibility to moisture is a problem.
Not quite as good as aramid, but far in excess of the volume fibres such as polyester. Its weakness is its resistance to oxidation bringing about strength loss and the higher application temperature, the lower the O2 level must be to compensate or a performance life reduction will occur:
Illustration of the relationship between oxygen, temperature and bag life for PPS
Typical applications for PPS needlefelts are:
| Power generation | Cemebt | Combustion processes |
| Incineration | Dryers | Carbon |
A unique distinguishing feature of PPS is that by weight it is actually about 30% sulphur:
This goes a long way to explaining the excellent limiting oxygen index figure of 34 which is above that quoted for meta aramid fibres. This means that the fibre won't support combustion in a normal atmosphere, but a burning dust cake or flame will obviously destroy the bags.
In common with other felts, PPS needlefelts can incorporate conductive fibres to reduce the possibility of static electricity build up. These are mainly steel because of the exposure temperatures. These help mitigate the potential of explosion with susceptible dusts, both our Checkstatic™ scrim and / or fibre blends can be used.
Because PPS products cannot hydrolyse, chemical treatments are not as common as with certain other fibres, but a number of systems are used. The major one by far being LR5, our liquid repellent finish, being used to protect the felt against the tendency of moist or oily dust cakes to adhere to the surface.
Temperature-wise, PPS is the highest rated thermoplastic fibre, and as such is the easiest to weld. It melts at about 285°C, hence its suitability up to about 190°C for short periods.
Its temperature range is quite extensive:
