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Valle Esudero, S.L
21 September 2017
In order correctly to choose the rubber that we need, the first thing we have to do is focus on these two properties which will help us make the correct choice of rubber:
  • The range of temperatures at which it is to be employed
  • The type of fluid.
To select the most suitable rubber the following information is required:
  1. What is the highest temperature that the rubber will withstand in service?
  2. What is the continuous temperatura?
  3. What is the lowest temperature at which the component can work?
  4. Which fluids will come into contact with the rubber and at what temperatura?
  5. Will the contact with the fluid be continuous, intermittent or occasional?
  6. Is the frequency of contact with the fluid continuous, intermittent, or very occasional (for example, accidental contamination)
  7. Is a long period of time or resistance to ozone an important factor?
The table below lists the different rubbers and their properties and price.

PRICE
FLUORO SILICON
RUBBER
PEAK MAX T
MAX  CONTINUOUS T
MÍNIMUM T
RESISTANCE/OILS/HC
HARDNESS
SHORE A
RESISTANCE TO THE ELEMENTS
2,5
Natural
105º C
75ºC
-60ºC
No
30-95º
No
2,5
EPDM
150ºC
130ºC
-50ºC
No
30-85º
No
5
Neoprene
125ºC
95ºC
-35ºC
Yes
30-90º
Yes
5
Nitrile
130ºC
100ºC
-20ºC
Yes
40-100º
Yes
7,5
Hypalon
160ºC
130ºC
-25ºC
Yes
40-85º
Yes
10
Acrylic
180ºC
150ºC
-20ºC
Yes
50-85º
Yes
10
Vamac
180ºC
150ºC
-40ºC
Yes
45-90º
Yes
20
Silicon
300ºC
205ºC
-60ºC
Yes
40-80º
Yes
37,5
Viton
300ºC
205ºC
-20ºC
Yes
50-95º
Yes
100
Fluoro silicon
280ºC
200ºC
-60ºC
Yes
40-80º
Yes
2,5
SBR
115ºC
85ºC
-55ºC
No
40-95º
No

When a rubber has been chosen sometimes one requires more detailed information to evaluate the suitability of the rubber for all aspects of the application.
Some of the typical properties required, depending on the application, are:
  • Minimum resistance to traction.
  • Minimum elongation at rupture and, when appropriate, por el módulo (es decir, mínimo esfuerzo de tracción a una tensión dada compresión 
Compression set
Many uses of rubber are applications of compression and it may be necessary to define the maximum fixed compression of a rubber when it is under load for a period of time. This is expressed as the percentage of the compression that is not recovered after compression is withdrawn.

In these cases it is necessary to fix both the quantity of compression and the T to which it is subjected plus the T at which the test is performed
Additional mechanical requirements should be specified only when necessary. They can be specified, for example, simply by the description "Good resistance to rupture necessary" or defined by the use of a specific test method (for example, ASTM or BS test methods).

If the properties required of the rubber are difficult to determine, the production of prototypes should be considered. Test pieces are manufactured for use in the real application. Once the material is shown to be suitable the required properties are defined.