BS ISO 815-1:2008 Rubber, vulcanized or thermoplastic. Determination of compression set. At ambient or elevated temperatures
Together with BSISO 815-2, BS ISO 815-1 cancels and replaces ISO 815:1991, as well as Technical Corrigendum ISO 815:1991/Cor.1:1993, which have been technically revised.
The main modifications concern changes in tolerances and the inclusion of the ageing ovens specified in ISO 188, with a view to improving the precision of the method.
ISO 815 consists of the following parts, under the general title Rubber, vulcanized or thermoplastic — Determination of compression set:
Part 1: At ambient or elevated temperatures
Part 2: At low temperatures.
BS ISO 815-1 specifies methods for the determination of the compression set characteristics of vulcanized and thermoplastic rubbers at ambient or elevated temperatures.
The methods are intended to measure the ability of rubbers of hardness within the range 10 IRHD to 95 IRHD to retain their elastic properties at specified temperatures after prolonged compression at constant strain (normally ) under one of the alternative sets of conditions described. For rubber of nominal hardness 80 IRHD and above, a lower compression strain is used: for a nominal hardness from 80 IRHD to 89 IRHD and for a nominal hardness from 90 IRHD to 95 IRHD.
When rubber is held under compression, physical or chemical changes can occur that prevent the rubber returning to its original dimensions after release of the deforming force. The result is a set, the magnitude of which depends on the time and temperature of compression as well as on the time and temperature of recovery. At elevated temperatures, chemical changes become increasingly more important and lead to a permanent set.
Short-time compression set tests, typically for , at elevated temperatures are commonly used as a measure of the state of cure, a means of material classification and a specification to ensure the quality of a compound. Longer tests, typically for , at elevated temperatures take account of the effect of ageing and are often used to predict service performance, including that of sealing materials. Short-time tests at ambient temperature show mainly the effect of physical changes (re-orientation of the molecular chains and the fillers).
Contents of BS ISO 815-1 contain:
- Scope
- Normative references
- Principle
- Apparatus
- Test pieces
- Test conditions
- Procedure
- Expression of results
- Precision
- Test report
- Precision
- Guidance for using precision results
BS ISO 815-1:2008 replaces BS 903-A6:1992 which remains current.
