Abstract
The paramount importance of producing the correct state of cure in a rubber article is too well known to need further emphasis. In the light of this, statement, the necessity of possessing a convenient and accurate method of assessing the state of cure is obvious. Before the advent of the T-50 test, the state of cure was measured mainly by a determination of the quantity of sulfur combined with the rubber, of stress-strain properties, or of optimum resistance to aging. The determination of combined sulfur has a disadvantage which is immediately apparent; it is laborious. Also, the figure obtained includes the amount of sulfur combined with metallic oxides used as activators, and to get an accurate measure of the quantity of sulfur combined with the rubber, a second analysis must be undertaken. There is yet another disadvantage, namely, that sulfur-containing substances added to the rubber mix interfere with the determination. The determination of tensile strength, modulus, or resistance to aging cannot be regarded as suitable for giving an accurate measure of cure, and are probably best looked on as complementary to the sulfur determination. With this state of affairs existing, it was only to be expected that, on the introduction of an entirely new and independent method of testing the state of cure, far-reaching claims should have been made, and also that the discovery should have been hailed as the elixir for all cure-testing ills. The present work was undertaken with a view to testing the validity of the claims put forward and to investigating, prior to the introduction of the T-50 as a routine test, the effect of variables likely to be encountered.