Shield integrated into seals using conductive elastomers
- Publisher
- Elsevier Science
- Year
- 2005
- Tongue
- English
- Weight
- 155 KB
- Volume
- 2005
- Category
- Article
- ISSN
- 1350-4789
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✦ Synopsis
German-based Freudenberg Dichtungs-und
Schwingungstechnik has introduced two material developments that are intended for growing areas of interest in the automotive industry.
One is a material that permits only minimal CO 2 permeation, and is considered to be suitable for the development of air-conditioning systems based on CO 2 .
ISC O-rings made of a new material, 85 HNBR 230861, offer low permeation at high CO 2 pressures of more than 100 bar, low swell in modern lubricating oils and resistance to explosive decompression. The use of CO 2 in refrigeration and air-conditioning systems offers potential environmental benefits, but requires operating conditions of up to 150 bar and 180°C, which represent a particular challenge to elastomeric seals. The problems of high permeability and potential for explosive decompression damage prompted Freudenberg to commence the development of a suitable material.
Tests were undertaken to determine if volume expansion, swelling and the occurrence of explosive decompression were directly related to one another. Tests showed that this was not the case. Explosive decompression can occur with high-volume expansion as well as low-volume expansion of less than 10%.
The new material has shown particular benefits in a temperature change test lasting several days, in which the temperature and pressure variations which frequently occur in air-conditioning units were simulated. As a result of the ongoing, changing thermodynamic equilibrium and the associated CO 2 solubility, the temperature change test subjects the material to higher material stress than that which occurs during a one-time, spontaneous decompression as a result of a leak.
Test series analyzing CO 2 permeation showed that permeation increases as temperature rises. The differences between the various materials in terms of their barrier properties, however, decrease as temperature rises and tend