PTFE Standard Compound
The values from the associated chart are obtained by the analysis of both the moulding and extrusion process. The ﬁrst column on the left sums-up the basic data of virgin PTFE G400, in order to compare with the values of the different compounds.
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PTFE STANDARD COMPOUND
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“G” COMPOUNDS AVAILABLE - FILLERS AND THEIR FUNCTIONS
In addition to virgin PTFE G400 products, GUARNIFLON® offers a wide range of compounded products as well.
Among these compounds, processed directly in Guarniflon® compounding unit starting from selected polymers and special high-purity fillers, end users are enabled to find the right answer to their technical requirements.
To make their selection easier, the following tables resume:
- the correlation among single fillers, properties and common uses
- properties of standard and special compounds among those most commonly marketed
Combinations of two or more fillers (not considered in the table) allow a large number of compounds.
Thus the resulting combined properties offer a variety of applications.
|Filler||Property||Most common applications|
|Glass||Enhanced wear resistance. |
Enhanced chemical resistance (except for alkali and hydrofluoric acid).
|Valve seats, seals, bearings, requested to resist sliding and chemicals. Suitable for bearings working at low PV values.|
|Graphite||Extremely low coefficient of friction. Fairly good compressive strength. Good wear resistance.||Bearings for high speed on fairly hard surface.|
|Carbon||Good thermal conductivity. Good resistance to deformation.||Valve seats. Bearings for high speed and when fast dissipation of electric charges is needed. Elastic bands for unlubricated compressors.|
|Molibdenum disulphide||Enhanced non-stick properties. Low static coefficient of friction. Fairly good resistance to deformation.||Guide bands. Details needing good resistivity.|
|Bronze||Enhanced compressive strength. Good wear resistance and high thermal conductivity.||Anti-extrusion rings. Unlubricated bearings for high speed on not hard surface.|
|Guarniflon® can offer an extremely wide range of skived tapes, sheets, extruded and moulded rods and tubes, in compounded PTFE from G series. Dimensions and relevant tolerances are included in the Dimensional Brochure. Tapes, sheets and finished products can be supplied etched.|
|Property||Test method||Unit||Virgin||G Standard Compounds|
15% GLASS FIBER
25% GLASS FIBER
25% SOFT CARBON
|Specific gravity||ASTM D792||g/cm3||2.14 - 2.18||2.19 - 2.22||2.20 - 2.26||2.10 - 2.15||2.05 - 2.11||2.05 - 2.11||3.75 - 3.93|
|Coefficient of linear thermal expansion 25-100¡C||ASTM D696||10-5 (mm/mm)/¡C||12 - 13||11 - 13||7.5 - 11||8 - 10||9 - 12||10 - 12||7 - 8|
|Hardness Shore D||ASTM D2240||Points||≥51||≥60||≥70||≥ 55||≥ 60||≥ 64||≥ 62|
|Tensile strength||ISO 527||N/mm2||≥24||≥17||≥17||≥18||≥15||≥14||≥15|
|Elongation at break||ISO 527||%||≥250||≥250||≥230||≥200||≥150||≥90||≥100|
|Compressive strength at 1% deformation||ASTM D695||N/mm2||4 - 5||6 - 7||8 - 9||6.5 - 7.5||7 - 9||7 - 9||10 - 11|
|Deformation under load (24 h 13.7 N/mm2 23¡C||ASTM D621||%||≤17||≤14||≤10||≤10||≤6.5||≤7||≤6|
|Permanent deformation (as above after 24 h relaxation)||ASTM D621||%||≤9||≤7||≤6.5||≤6||≤4||≤5||≤2.5|
|Kinetic coefficient of friction||ASTM D1894||/||0.03||0.12||0.13||0.07||0.13||0.11||0.13|
|Wear factor at PV 100||ASTM D3702||2.900||10 - 20||10 - 15||60||20 - 30||16 - 20||10|
|Specific gravity||ASTM D792||g/cm3||2.14 - 2.18||2.18 - 2.21||2.18 - 2.26||2.09 - 2.14||2.04 - 2.10||2.04 - 2.10||3.80 - 3.88|
|Hardness Shore D||ASTM D2240||Points||≥40||≥ 60||≥60||≥ 55||≥ 60||≥ 64||≥ 65|
|Tensile strength||ISO 527||N/mm2||≥20||≥15||≥13||≥ 14||≥15||≥12||≥13|
|Elongation at break||ISO 527||%||≥ 200||≥200||≥180||≥150||≥50||≥50||≥80|
PROPERTIES FOR DESIGNING
Fillers blended with PTFE allow to improve some basic physical properties of virgin polymers.
The advantages are the following:
- enhanced compressive strength
- enhanced thermal conductivity
- reduced thermal expansion
- reduced wear factor
When talking about the material mechanical properties, tensile strength and elongation at break are usually the topics before others. However, these two properties, though the most common ones, do not always carefully reflect the behavior of the material itself in some applications, while compressive properties are actually the most important ones. We’d highlight compressive strength at a set deformation, deformation under constant load and permanent deformation at a set temperature.