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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

The following table shows the way each filler affects physical and mechanical properties.
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
				G400	G403 15% GLASS FIBER	G405 25% GLASS FIBER	G412 15% GRAPHITE	G415 25% SOFT CARBON	G453 25% CARBOGRAPHITE	G458 60% BRONZE 2% CARBON
Moulded
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
Extruded
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

MECHANICAL PROPERTIES
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.