ASTM D5669-95

1.1 This test method covers a technique for evaluating a parameter, derived from curemeter testing of a standard hydrogenated nitrile rubber (HNBR) formulation, that is related to the percent residual unsaturation of the HNBR. The standard materials, test formulation, and mixing procedure are fully described. This test method is applicable to all grades of HNBR in the raw unvulcanized state.

1.2 The evaluation of the unsaturation parameter, designated by UP, is based on special regression equations developed from the measured values for two curemeter parameters versus the percent unsaturation measured by infrared spectrophotometry as defined by Test Method D5670. The data used for this are contained in Appendix X1.

1.2.1 The use of a curemeter and a standard formulation to evaluate the residual unsaturation in HNBR has the advantage of being a relatively simple test, available to most rubber testing laboratories. The disadvantage lies in the nonlinear relationship between HNBR unsaturation and the measured curemeter parameters of scorch time, tS1 and maximum curemeter torque, MH.

1.2.2 The use of UP , which is calculated from a scorch time parameter and a maximum torque parameter, both of which are obtained from Table A1.1 permits the development of a more realistic relationship of the unsaturation levels among a group of HNBR samples than the less definitive technique of simple ranking. The ranking technique is not definitive because the relationship between the curemeter parameters and the unsaturation is highly nonlinear. Curemeter ranking of a series of HNBR samples at low true unsaturation compared to the ranking of a series of samples at high true unsaturation, may give misleading indications of unsaturation differences among the group of rubbers.

1.2.3 If, , the unsaturation in percent of a tested HNBR sample is known, it can be used to calculate the approximate unsaturation (in percent) of unknown HNBR samples.

1.3 Mixing and curemeter testing variations, both within and between laboratories, may influence the results as obtained by this test method. These variations will be smaller for within-laboratory testing.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.