Composite yarn for the manufacturing of braided packings, braided packing and process for forming the composite yarn

摘要

A composite yarn is for making braided packing for sealing pump or rotating valve shafts. The packing comprises an external layer and a core. Preferably, the external layer is made of expanded polytetrafluoroethylene (PTFE) impregnated with graphite, and the core is an aramide filament. The graphite impregnated, expanded PTFE gives the composite yarn good thermal conductivity, high capacity of friction reduction and good resistance to chemical attacks. The aramide filament has high mechanical strength. The composite yarn can be braided to form a packing where only the PTFE contacts the shaft, thus protecting it against uneven wear.