ASTM D6049-03

The viscous and elastic behavior of unvulcanized rubbers and rubber compounds is of paramount importance in rubber manufacturing, since it affects processing, such as mixing, calendering, extrusion, and molding. The uniformity of these properties is equally important, as fluctuations will cause upsets in manufacturing processes.

A test capable of measuring viscosity and elasticity of unvulcanized rubbers and rubber compounds, including their uniformity and prediction of processing behavior, is therefore highly desirable (see Practice D 6048 for further information).

Compared to many other rheological tests, this test method measures viscosity and elasticity related parameters under conditions of low shear and has a high discriminating power. It can detect small rheological differences. A full discussion of the principles behind stress relaxation testing is given in Practice D 6048.

Test results of this test method may be useful in predicting processability, but correlation with actual manufacturing processes must be established in each individual case, since conditions vary too widely.

This test method is suitable for specification compliance testing, quality control, referee purposes, and research and development work.

1.1 This test method is an adaptation of the German Standard DIN 53514, a further development of the former "Defo Test" (see Appendix X1).

1.2 This test method is capable of measuring and characterizing the rheological behavior (viscosity and elasticity) of unvulcanized raw rubbers and rubber compounds, relating to the macro structure of rubber polymers (average molecular weight, molecular weight distribution, long chain branching, and micro- and macro-gel).

1.3 The viscosity and elasticity of unvulcanized rubbers and rubber compounds are determined by subjecting cylindrical test pieces to a compression/recovery cycle. The dependency on shear rate at constant shear stress is evaluated and the material fatigue behavior is determined in repeat cycle testing.

1.4 The non-Newtonian viscous and elastic behavior of rubbers and rubber compounds can also be evaluated.

1.5 Statistical evaluation of the test data provides an indication of data variation, which may be employed as an estimate of the homogeneity of the material tested.

1.6 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.

1.7 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.