Machining PTFE GF25

PTFE GF25 is a PTFE (polytetrafluoroethylene) filled with 25 % glass fibre. The glass-fibre content remedies the two main weaknesses of virgin PTFE – low compressive strength and pronounced cold flow (creep) – and at the same time markedly increases wear resistance. The typical PTFE advantages are retained: almost universal chemical resistance, a very low coefficient of friction, a service range from -200 to +260 °C and non-flammability. This makes GF25 the standard compound for loaded sliding, sealing and bearing elements.

PTFE GF25 machines well – turning, milling, drilling and sawing give clean results; because of the glass-fibre content we use sharp, wear-resistant tools and ensure dust extraction. We consistently avoid overheating. This is how we reliably produce load-bearing sealing, sliding and bearing parts – from single pieces to series production.

PTFE GF25 is worthwhile when the advantages of PTFE must be combined with higher mechanical load capacity – for example:

• Seals, sealing rings and guide bands under pressure and wear loading
• Plain bearings, wear strips and guiding elements
• Piston rings and sealing elements in compressors and pumps
• Valve seats and components in chemical process technology
• Chemically loaded sliding and sealing parts up to 260 °C

PTFE materials are among the higher-priced engineering plastics; PTFE GF25 is in the range of virgin PTFE or slightly below (glass fibre is cheaper than PTFE powder). The part price is mainly determined by semi-finished shape and dimension, material utilisation (offcut), machining effort and lot size. We are happy to quote binding prices on request based on your drawing.

Equally important are the limits of the material:

• Contact with hydrofluoric acid, fluorine or molten alkali metals (attack)
• Applications with strong hot alkalis (glass fibre is attacked)
• Unambiguous food contact without verification (then virgin/FDA PTFE)
• Applications requiring high impact strength or elongation
• Joining by welding – not possible for PTFE (machining only)

An honest assessment – and how the disadvantages can be mitigated in practice: Advantages:

Disadvantages:

Practical tip: PTFE GF25 is the right choice when PTFE properties meet compressive, wear and creep loading – for example in seals, piston rings and plain bearings. If unambiguous food contact or maximum chemical resistance against hydrofluoric acid/alkalis matters, virgin PTFE is the better choice; for higher hardness and wear resistance at lower abrasiveness, carbon-fibre- or bronze-filled PTFE grades are an alternative.

• Markedly higher compressive and wear resistance than virgin PTFE
• Reduced creep (cold flow) under continuous load
• Almost universal chemical resistance retained
• Very low friction, -200 … +260 °C, non-flammable
• Good electrical insulator
• Not resistant to hydrofluoric acid, fluorine, hot strong alkalis
• Lower elongation/toughness than virgin PTFE
• Filled grade – food contact only with verification
• Not melt-processable/weldable (machining only)
• Higher price than standard plastics