COMPARISONS OF METHODS OF STATE-OF-CURE DETERMINATION.

The DSC method of relative state-of-cure determination is preferred due to the ability to use a small irregular sample and because of the short time required to run a test. This method is limited, however, to materials with a sufficiently high heat of vulcanization. The time required to reach 80% conversion at 142 degree C for Y156B-2 as measured by DSC is 19 minutes. This time to 80% conversion is for reference in comparing test methods only. The Mooney-Rivlin method of relative state-of-cure determination is a useful method for those elastomers which do not lend themselves to the DSC method. The small strain modulus (C//1 plus C//2) should be used instead of the more rigorous C//1 measurement. The two-solvent technique of the solvent swell method of relative state-of-cure determination is a good procedure for determing X for a solvent-polymer pair. The solvent swell method in general is not recommended for this type of state-of-cure measurement due to poor resolution at higher states-of-cure.