Texture/Surface Finish
The finish of rubber can range from semi-gloss to extremely matt using the same mould, not comparable to plastic surface. Depending on the machining processes to achieve the part design, this has impact on cost of tool.
Differing textures on the same product may give visual differences on the colour.
VDI 3400 |
ISO, VDI, ASA |
ISO/TC 213 |
Char Milles |
Ra=CLA=AA |
Rz |
|
CH |
um |
uinch |
um |
|
0.025 |
1 |
|
N1 |
0.05 |
2 |
N2 |
0 |
0.1 |
4 |
N3 |
1 |
0.11 |
4 |
2 |
0.12 |
5 |
3 |
0.14 |
6 |
4 |
0.16 |
6 |
5 |
0.18 |
7 |
6 |
0.2 |
8 |
N4 |
7 |
0.22 |
9 |
8 |
0.25 |
10 |
9 |
0.28 |
11 |
10 |
0.32 |
13 |
11 |
0.35 |
14 |
12 |
0.4 |
16 |
1.5 |
N5 |
13 |
0.45 |
18 |
|
14 |
0.5 |
20 |
15 |
0.56 |
22 |
2.4 |
16 |
0.63 |
25 |
|
17 |
0.7 |
28 |
|
18 |
0.8 |
32 |
|
N6 |
19 |
0.9 |
36 |
|
20 |
1 |
40 |
|
21 |
1.12 |
45 |
4.7 |
22 |
1.26 |
50 |
|
23 |
1.4 |
56 |
|
24 |
1.62 |
63 |
6.5 |
N7 |
25 |
1.8 |
72 |
|
26 |
2 |
80 |
|
27 |
2.2 |
88 |
10.5 |
28 |
2.5 |
100 |
|
29 |
2.8 |
112 |
|
30 |
3.2 |
125 |
12.5 |
N8 |
31 |
3.5 |
140 |
|
32 |
4 |
160 |
|
33 |
4.5 |
180 |
17.5 |
34 |
5 |
200 |
|
35 |
5.6 |
224 |
|
36 |
6.3 |
250 |
24 |
N9 |
37 |
7 |
280 |
|
38 |
8 |
320 |
|
39 |
9 |
360 |
34 |
40 |
10 |
400 |
|
41 |
11.2 |
448 |
|
42 |
12.6 |
500 |
48 |
N10 |
43 |
14 |
560 |
|
44 |
16 |
640 |
|
45 |
18 |
760 |
69 |
Tolerance
Rubber has a higher shrinkage value than plastic, please refer to ISO 3302-1 tolerance table for rubber parts.
Tolerances For Moulded Parts - Rubber
Acc. To ISO 3302-1 |
Nominal dimension
(mm) |
Tolerance Class M1 |
Tolerance Class M2 |
Mould dependant dimensions |
Dimension with Overflow |
Mould dependant dimensions |
Dimension with Overflow |
Tolerances – in mm |
Tolerances – in mm |
> |
0 |
- |
4.0 |
± 0.08 |
± 0.10 |
± 0.10 |
± 0.15 |
> |
4.0 |
- |
6.3 |
± 0.10 |
± 0.12 |
± 0.15 |
± 0.20 |
> |
6.3 |
- |
10 |
± 0.10 |
± 0.15 |
±0.20 |
± 0.20 |
> |
10 |
- |
16 |
± 0.15 |
± 0.20 |
± 0.20 |
± 0.25 |
> |
16 |
- |
25 |
± 0.20 |
± 0.20 |
± 0.25 |
± 0.35 |
> |
25 |
- |
40 |
± 0.20 |
± 0.25 |
± 0.35 |
± 0.40 |
> |
40 |
- |
63 |
± 0.25 |
± 0.35 |
± 0.40 |
± 0.50 |
> |
63 |
- |
100 |
± 0.35 |
± 0.40 |
± 0.50 |
± 0.70 |
> |
100 |
- |
160 |
± 0.40 |
± 0.50 |
± 0.70 |
± 0.80 |
|
|
|
|
Tolerances – in % |
Tolerances – in % |
> |
|
160 |
|
± 0.30 |
± 0.40 |
± 0.50 |
± 0.70 |
Table classes M1 (Precision) and M2 (Commercial)
* To achieve M1 class, lesser cavities are required, resulting in higher part cost
Tensile Strength
Tensile strength is the maximum tensile stress reached in stretching a test piece.
Tensile tests are used for controlling product quality and for determining the effect of chemical or thermal exposure or an elastomer. In the latter case, it is the retention of these physical properties, rather than the absolute values of the tensile stress, elongation or modulus, that is significant.
Grade |
Typical Range |
Natural |
10 to 15 Mpa |
SBR |
9 to 12 Mpa |
EPDM |
7 to 15 Mpa |
CR |
9 to 14 Mpa |
NBR |
7 to 20 Mpa |
Silicone |
4 to 10 Mpa |
HNBR |
7 to 10 Mpa |
FKM |
5 to 9 Mpa |
FluoroSilicone |
6 to 12 Mpa |
PU |
9 to 15 Mpa |
Compression Set
The permanent deformation remaining after release of a compressive stress.
Compression set is expressed as the percentage of the original specimen thickness for Method A (constant force) or the percentage of the original deflection for Method B (constant deflection).
Compression set is an important property for elastomers and cushioning materials.
24 hours @ 70°C
Grade |
Typical Value |
Tight Value |
Natural |
30% |
20% |
SBR |
30% |
20% |
EPDM |
30% |
15% |
CR |
40% |
20% |
NBR |
30% |
20% |
Silicone |
20% |
10% |
HNBR |
30% |
20% |
FKM |
35% |
20% |
FluoroSilicone |
20% |
10% |
PU |
35% |
20% |
Electrical Properties
Rubber is often used as an electrically insulating material, when formulated; it can offer outstanding electrical properties.
Electrical properties are dependent on the materials used in compounding and requirements should be clearly defined.
Surface resistivity is the resistance to leakage current along the surface of an insulating material.
Surface Resistivity is expressed in ohms (per square) and a practice to measure on compounding sheet level.
Ohms Per Square |
Resistivity |
103 - 104 |
Conductive |
106 - 1011 |
Static |
> 1012 |
Insulative |