Group of elastic materials, which become soft (thermoelastic) when energy is added (temperature increase), where moulded parts lose their form (voltage). When cooling, plastification of the materials may occur This process can be repeated as desired.
Seals or sealing parts made of thermoplastics must therefore not be heated above a certain limiting temperature, as otherwise they will lose their pre-load. Important thermoplastics for seals include:
PTFE (polytetrafluoroethylene, e.g. Teflon) has extremely low friction and has excellent chemical resistant strength (even against HFD fluids) and very high temperature resistance from –270° to +260° C. PTFE is used in seals with an elastomer core and in the case of sliding rings and guide rings with filler materials.
PA (polyamide, e.g. nylon) has good sliding properties and is low-wearing, but has high water absorption (swelling).
POM (polyacetal, e.g. Delrin) has high mechanical strength, result in parts with a high degree of dimensional accuracy. Material commonly used for back rings,guide rings and scraper rings.