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ISO 815-1 2nd Edition, September 1, 2014 Rubber, vulcanized or thermoplastic - Determination of compression set - Part 1: At ambient or elevated temperatures
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Availability date: 07/13/2021
Description / Abstract:
This part of ISO 815 specifies methods for the determination of
the compression set characteristics of vulcanized and thermoplastic
rubbers at ambient (one method) or elevated temperatures (three
methods, A, B, and C, depending on the way the test piece is
released at the end of the test).
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 25 %) under one of the
alternative sets of conditions described. For rubber of nominal
hardness 80 IRHD and above, a lower compression strain is used: 15
% for a nominal hardness from 80 IRHD to 89 IRHD and 10 % for a
nominal hardness from 90 IRHD to 95 IRHD.
NOTE 1 When rubber is held under compression, physical or
chemical changes that prevent the rubber returning to its original
dimensions after release of the deforming force can occur. The
result is a set, the magnitude of which depends on the time and
temperature of compression as well as on the time, temperature, and
conditions of recovery. At elevated temperatures, chemical changes
become increasingly more important and lead to a permanent set.
NOTE 2 Short-time compression set tests, typically for 24 h, 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 1 000
h, 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).