iglidur® L250 - Material data

Materials table

General features	Unit	iglidur® L250	test method
Density	g/cm³	1,50
Colour		Beige
Max. humidity absorption at 23°C/50% R. H.	% weight	0,7	DIN 53495
Max. water absorption	% weight	3,9
Coefficient of surface friction, dynamic, against steel	μ	0,08–0,19
PV values max. (dry)	MPa x m/s	0,4
Mechanical properties
Bending E-module	MPa	1.950	DIN 53457
Tensile strength at +20 °C	MPa	67	DIN 53452
compressive strength	MPa	47
Maximum recommended surface pressure (20° C)	MPa	45
Shore D hardness		68	DIN 53505
Physical and thermal properties
Max. long term application temperature	°C	+90
Max. short term application temperature	°C	+180
Upper short-term ambient temperature¹⁾	°C	+200
Lower application temperature	°C	-40
Heat conductivity	W/m x K	0,24	ASTM C 177
Coefficient of thermal expansion (at 23° C)	K^-1 x 10^-5	10	DIN 53482
Electrical properties
Specific forward resistance	Ωcm	> 10¹⁰	DIN IEC 93
Surface resistance	Ω	> 10¹¹	DIN 53482
¹⁾ Without additional load; no gliding movement; relaxation not excluded.

'Table 01: Material Data

Figure 01: Permitted PV values for iglidur® L250 bearings with 1 mm wall thickness in dry operation against a steel shaft, at 20°C, installed in a steel housing.

X = Surface speed [m/s]
Y = Load [MPa]

iglidur® L250 is a bearing material for high rotary speeds, fast gliding movements and low coefficients of friction. The iglidur® L250 material can feature these advantages particularly with low loads. Applications which feature these advantages are fans, small motors, fast-running sensors or the magnet technology.

Figure 02: Maximum recommended surface pressure dependent on the temperature (45 MPa to +20 °C)

X = Temperature [°C]
Y = Load [MPa]

Mechanical properties

Maximum recommended surface pressure represents a mechanical material parameter. Tribological conclusions cannot be drawn from it. With increasing temperatures, the compressive strength of iglidur® L250 plain bearings decreases. Fig. 02 clarifies this connection.

Figure 03: Deformation under load and temperatures

X = Load [MPa]
Y = Deformation [%]

Fig. 03 shows the elastic deformation of iglidur® L250 during radial loading. The deformation amounts to less than 3% at the maximum recommended surface pressure of 45 MPa. A plastic deformation can be negligible up to this value. It is however also dependent on the period of exposure.

Load, surface pressure

Maximum surface speed

m/s	Rotary	oscillating	Linear
Constant	1	0,7	2
Short-term	1,5	1,1	3

Table 02: Maximum surface speeds

Permitted surface speeds

iglidur® L250 has been developed especially for high surface speeds with low loads. Besides the physical limit, which is preset by the heating of the bearing, the coefficients of wear also act limitedly if rapidly high glide paths emerge at high peripheral speeds and the permitted wear limit is thus reached earlier. The maximum speeds can be gathered from Table 02.

Surface speed

p x v value and lubrication

iglidur® L250	Operating temperature
Lower	- 40 °C
Upper, long-term	+ 90 °C
Upper, short-term	+ 180 °C
Secure axially in addition	+ 55 °C

Table 03: Temperature limits for iglidur® L250

Temperatures

The iglidur® L250 bearings can be used in temperatures up to 180° C for the short-term. Note that a mechanical securing of the bearing is recommended from temperatures of 55° C. Higher temperatures can also cause the bearing to lose its press-fit seating and move in the bore.

Temperatures, coefficient of thermal expansion

Figure 04: Coefficients of friction dependent on the surface speed, p = 0,75 MPa

X = Surface speed [m/s]
Y = Coefficient of friction μ

Friction and wear

In the best pairing (with V2A shafts), friction coefficients of 0.14 are already reached with low loads. Coefficients of friction under 0.1 was already measured at 10 MPa. (Fig. 04 and 05).

iglidur® L250	Dry	Grease	Oil	Water
Coefficients of friction µ	0,08 - 0,19	0,09	0,04	0,04

Table 04: Coefficients of friction for iglidur® L250 against steel
(Ra = 1 µm, 50 HRC)

Coefficients of friction

Wear resistance

Figure 05: Coefficients of friction dependent on the load, v = 0,01 m/s

X = Load [MPa]
Y = Coefficient of friction μ

Fig. 06: Wear, rotating application with various

Figure 06: Wear, rotating application with different shaft materials, p = 1 MPa, v = 0,3 m/s

X = Shaft material
Y = Wear [μm/km]

A = Aluminum, hard-anodized
B = machining steel
C = Cf53
D = Cf53, hard chrome-plated
E = St37
F = V2A
G = X90

Shaft materials

As seen in Figure 06, many shafts are recommendable for low loads and low rotations.

The good coefficients of friction are additionally retained over a wide range of recommendable surface finishes for shafts. For loads greater than 1 MPa, particular attention should be paid to the shaft material used.

Shaft materials

Fig. 07: Wear in rotating and oscillating applications with shaft material

Fig. 07: Wear with oscillating and rotating applications with Cf53 shaft material dependent on the load

X = Load [MPa]
Y = Wear [μm/km]

A = Cf53, rotating
B = Cf53, oscillating

Medium	Resistance
Alcohols	+ to 0
Hydrocarbons	+
Fats, oils, without additives	+
Fuels	+
Diluted acids	0 to -
Strong acids	-
Diluted bases	+
Strong bases	0

+ resistant 0 partially resistant - non-resistant
All specifications at room temperature [+20℃]
Table 05: Chemical resistance of iglidur® L250

Electrical properties

Specific forward resistance	> 10¹⁰ Ωcm
Surface resistance	> 10¹¹ Ω

Chemical resistance

iglidur® L250 bearings are resistant to diluted alkalis and very weak acids as well as to solvents and all kinds of lubricants.

Radioactive rays

iglidur® L250 bearings are radiation resistant up to a radioactive intensity of 3 x 10⁴ Gy. Higher radiation affects the material and may potentially lead to a notable lowering of value of an important mechanical property.

UV-resistant

iglidur® L250 plain bearings change colour under the influence of UV rays. However, their properties do not deteriorate.

Vacuum

In application in vacuum, the potentially existent humidity is degassed. For this reason only the dry iglidur® L250 bearings are suitable for vacuum.

Electrical properties

The bearings are electrically insulating.

Maximum moisture absorption
by +23 °C/50 % r. F.	0,7 Wt.-%
Max. water absorption	3,9 Wt.-%

Table 06: Moisture absorption

Effect of moisture absorption on plain bearings

Diagram 10: Effect of moisture absorption

X = Moisture absorption [weight %]
Y = Reduction of inside diameter [%]

humidity absorption / moisture absorption

Please take into account the humidity absorption in applications in which very minor bearing clearances occur.

Diameter d1 [mm]	Shaft h9 [mm]	iglidur® L250 E10 [mm]	Housing H7 [mm]
Up to 3	0 - 0,025	+0,014 +0,054	0 +0,010
> 3 to 6	0 - 0,030	+0,020 +0,068	0 +0,012
> 6 to 10	0 - 0,036	+0,025 +0,083	0 +0,015
> 10 to 18	0 - 0,043	+0,032 +0,102	0 +0,018
> 18 to 30	0 - 0,052	+0,040 +0,124	0 +0,021
> 30 to 50	0 - 0,062	+0,050 +0,150	0 +0,025
> 50 to 80	0 - 0,074	+0,060 +0,180	0 +0,030
> 80 to 120	0 - 0,087	+0,072 +0,212	0 +0,035
> 120 to 180	0 - 0,100	+0,085 +0,245	0 +0,040

Table 07: Important tolerances iaw. ISO 3547-1 after press-fitting.

Installation tolerances

iglidur® L250 plain bearings are standard bearings for shafts with h-tolerance (recommended minimum h9). After the installation in a housing with nominal diameter, the inner diameter of the bearing automatically adjusts to the E10 tolerance. In certain dimensions the tolerance in dependence on the wall thickness deviates from this (See delivery program )