iglide® M250 - Material data
| General features | Unit | iglide® M250 | Test method |
|---|---|---|---|
| Density | g/cm3 | 1.14 | |
| Color | Charcoal | ||
| Max. humidity absorption at 73° F/50% R. H. | Wt.-% | 1.4 | DIN 53495 |
| Max. water absorption | Wt.-% | 7.6 | |
| Coefficient of surface friction, dynamic, against steel | µ | 0.18-0.40 | |
| p x v value, max. (dry) | psi x fpm | 3,400 | |
| Mechanical properties | |||
| Modulus of elasticity | psi | 391,600 | DIN 53457 |
| Tensile strength at 68°F | psi | 16,240 | DIN 53452 |
| Compressive strength | psi | 7,542 | |
| Permissible static surface pressure (68 °F) | psi | 2,901 | |
| Shore D hardness | 79 | DIN 53505 | |
| Physical and thermal properties | |||
| Max. long-term application temperature | °F | 176 | |
| Max. short-term application temperature | °F | 338 | |
| Min. application temperature | °F | -40 | |
| Thermal conductivity | [W/m x K] | 0.24 | ASTM C 177 |
| Coefficient of thermal expansion (at 73.4° F) | [K-1] x 10-5] | 10 | DIN 53752 |
| Electrical properties | |||
| Specific volume resistance | Ωcm | > 1013 | DIN IEC 93 |
| Surface resistance | Ω | > 1011 | DIN 53482 |
Permitted p x v values
For iglide® M250 plastic bushings with 0.03 in wall thickness in dry operation against a steel shaft, at 68° F, installed in a steel housing.
The M250 distinguishes itself by its impact strength, vibration dampening and wear resistance. They prove to be particularly good under stresses in which the vibration dampening of the bushing is called for, for instance in sports equipment and packaging machines. As they are also in a position to tolerate dirt, they are ideal for use in agricultural machinery and garden equipment.
Figure 4.2: Deformation under load and temperatures
Compressive Strength
iglide® M250 plastic bushings have a maximum recommended surface pressure of 2900 psi. The deformation at room temperature is under 2%. Compared with other iglide® materials, the iglide® M250 plastic bushings are very elastic. By this elasticity they can yield very well, but reset again. A plastic deformation is negligible up to the maximum recommended surface pressure.
Permitted surface speeds
iglide® M250 is finished with greater wall thickness in the standard product range. As this lowers the conduction of frictional heat, the iglide® M250 plastic bushings are mainly considered for low to medium surface speeds. The maximum permitted surface speeds in the dry operation are 157 fpm (rotating) and 492 fpm (linear) respectively.
| fpm | Rotating | Oscillating | Linear |
|---|---|---|---|
| Constant | 157 | 118 | 492 |
| Short-term | 393 | 275 | 984 |
Temperatures
The short-term permitted maximum temperature is 338° F. The iglide® M250 plastic bushings should however be exposed to this temperature only without any more load. The long-term permitted application temperature lies at 176° F. Here you'll find the wear limit, thus also the temperature at which the wear increases disproportionately.
| iglide® M250 | Application temperature |
|---|---|
| Lower | - 40 °F |
| Upper, long-term | + 176 °F |
| Upper, short-term | + 338 °F |
| Additional axial securing | + 140 °F |
Friction and wear
The coefficient of friction µ of a plastic bushing is, among other things, influenced by surface speed and load. If the load remains constant, the coefficient of friction rises with increasing speed
In contrast, a lone increase of the load at constant speed results in a reduction of the coefficient of friction
Friction and wear depend also strongly on the surface of the shaft. For iglide® M250 plastic bushings a ground surface with an average roughness of 24 rms is recommended for the shaft.
| iglide® M250 | Dry | Grease | Oil | Water |
|---|---|---|---|---|
| Coefficients of friction µ | 0.18-0.40 | 0.09 | 0.04 | 0.04 |
Fig. 2.7: Wear, rotating application with different shaft materials, load p = 108 psi, v = 98 fpm
Shaft materials
The diagrams 4.8 and 4.9 display a summary of the results of tests with different shaft materials conducted with plastic bushings made of iglide® M250.
In rotations, the shaft material plays only a comparably minor role up to loads of 290 psi. Figure on the left shows at a glance the shaft materials best suited for low loads.
If the load increases, the wear of some pairings increases markedly. For this reason, a suitable shaft material should be considered with high loads. These are the hard shafts, for example Cold Rolled Steel or hard-chromed shafts, if the wear resistance is viewed in isolation.
The graph clarifies that the iglide® M250 is essentially better for rotating and pivoting operations. Here it must be mentioned that in practice the vibrations acting on the bushing are often extremely high in pivoting movements. Here the iglide® M250 can exercise its particularly dampening properties. In our test such vibrations are excluded, so that the comparison between rotation and pivoting operation amazes at first.
Installation tolerances
iglide® M250 bushings require relatively large bushing clearances for optimum performances. These ensure that the bushings remain reliable even with thermal expansion and water absorption.
These clearances, which would have been unacceptable for a metallic bushing, only enable the iglide® M250 plastic bushing to display its best qualities such as wear resistance and freedom from maintenance. The disadvantages of the bushing clearance are again compensated by the vibration dampening properties.
After the installation in a housing bore with the tolerance H7, the inner diameter of the bushing automatically adjusts to the D11 tolerance. The shaft should have a minimum H9 tolerance.
| Diameter d1 [inch] | Shaft h9 [inch] | iglide® M250 D11 [inch] |
|---|---|---|
| Up to 0.019685 | 0 - 0.0009843 | +0.0007874 + 0.0031496 |
| > 0.1181 to 0.2362 | 0 - 0.0011811 | +0.0011811 + 0.0041339 |
| > 0.2362 to 0.3937 | 0 - 0.0014173 | +0.0015748 + 0.0051181 |
| > 0.3937 to 0.7087 | 0 - 0.0016929 | +0.0019685 + 0.0062992 |
| > 0.7087 to 1.1811 | 0 - 0.0020472 | +0.0025591 + 0.0076772 |
| > 1.1811 to 1.9685 | 0 - 0.0024409 | +0.0031496 + 0.0094488 |
Chemical resistance
iglide® M250 plastic bushings have a good resistance against chemicals. They are resistant to most lubricants. The iglide® M250 is not affected by most weak organic and inorganic acids.
The humidity absorption of iglide® M250 plastic bushings amounts to about 1.4% in standard climatic conditions. The saturation limit in water is 7.5%. This should be considered according to application conditions.
Radioactive rays
Plastic bushings made of iglide® M250 are conditionally usable under radioactive radiation. They are resistant up to a radiation intensity of 1,000 Gy.
UV-resistant
iglide® M250 plastic bushings are permanently resistant to UV rays.
Vacuum
The iglide® M250 plastic bushing degasses potentially available humidity in vacuum. The relatively high humidity absorption of the plastic bushing therefore permits the bushing to be used in vacuum only restrictedly.
| Medium | Resistance |
|---|---|
| Alcohol | + to 0 |
| Hydrocarbons, chlorinated | + |
| Greases, oils, without additives | + |
| Fuels | + |
| Weak acids | 0 to - |
| Strong acids | - |
| Weak alkaline | + |
| Strong alkaline | 0 |
| + resistant 0 conditionally resistant - non-resistant |
Electrical properties
Plastic bushings made of iglide® M250 are electrically insulating.
| Specific volume resistance | Surface resistance |
|---|---|
| > 1013 Ωcm | > 1011 Ω |