PTFE Sliding Bearing Tapes
Physical properties :
|
Specific weight |
3,05 ± 0,05 |
g/cm3 |
|
Water absorption |
0,01 max |
% |
|
Linear expansion coefficient |
6.10-5 |
1/K |
|
Thermal conductivity at 20°C |
0,8 |
W/m-K |
Mechanical properties :
|
Max. compression load on 1 % deformation |
9,3 | N/mm2 |
|
Tensile resistance |
17 min. | N/mm2 |
|
Extension |
220 min. | % |
|
Elasticity |
1000 | N/mm2 |
|
Hardness |
Shore | 60 ± 5 |
Temperature range
Operation temperature should not exceed -40 °C and + 80 °C. On increasing temperature the compression strength is reduced. Corresponding provision to balance the above-mentioned would be a sufficient heat removal due to lubrication.
It has to be noted that, on a short-term temperature rise, the material breakage will not occur, but its slow deformation.
Stability
The casing substance has a good chemical stability. Humidity intake amounts to 0.01 % at the maximum, and causes no substantial dimension change. The casing material is resistant against cooling, cleaning, and lubrication means.
Counter-running surfaces
As the counter-running material mostly steel or cast iron is used. Preferential are hardened counter-running surfaces and these should feature the hardness ca 60HRc; cast iron surfaces the hardness ca 240 HB. Quality of the counter-running surfaces is essential.
Skid resistance of surface areas
St = Ra = 0,2 to 0,4 μm
GG = Ra = 0,2 to 0,8 μm
So as to reach the longest possible service life, the skid resistance is to be maintained. Higher skid resistance results in higher wear, while lower skid resistance results in the suction effect, which results in increased friction.
Fixing the casing substance
The casing material is fixed by bonding to metal guide elements. The casing material is delivered ready for bonding.
Preparation of bonded metal surfaces
On bonding, the casing material chip working of the bonded surface is essential for optimum results. The roughness of the surface areas maintains the adhesive effect of the bond up to a certain level. Additional possible roughening of the surface areas is reached by sanding and additional abrasion by abrasive paper (grain size: 100).
Roughness of the bonded surface
Ra = 0,8 - 3,2 μm
Cleaning of the bonded surface
Prior to bond application the bonded surfaces must be cleaned very properly and relieved of oil, grease, dust, and rust.
Impurities are to be removed by washing with common degreasing agents as perchloro-ethylene, trichlorethylene, acetone, etc..
Bonding of casing material
If possible, the bonding of the casing material is to be performed in rooms designated thereto, normally tempered. Two-component bonds must be used, with good cutting and tearing strength. After mixing, the bond parts should be applied to the cleaned guide surface with a spatula; thereto the casing material is then laid and evenly pressed. Within a prescribed setting time parts must not be moved any more. Working comes on after the bond having been set.