Technical Notebook: Proposed changes to established ASTM rubber processability methods

There are presently over 10 different standard RPA ASTM test methods that are used to measure rubber processability.

The RPA is used in three of these standards:

• ASTM D6204 Parts A, B and C (RPA Frequency Sweeps and VTA Curing);
• ASTM D6601 (RPA Strain Sweeps of in situ Cured Dynamic Properties); and
• ASTM D8059 (RPA Strain Sweep using the Payne Effect Method for State of Mix).

To improve these three methods further, ASTM Sub Committee D11.12 under D11 Main Committee on Rubber is working on adding a new Part D to ASTM D6204 (a high-strain sweep in the non-linear viscoelastic region) to improve statistical test sensitivity to differences in the quality of mixed stocks and raw polymers. A new Part E also is proposed for using FT Rheology (LAOS) to also improve test sensitivity.

In addition, work is underway to widen the scope of ASTM D6601 by adding an optional Part B to allow sub ambient temperature strain sweep measurements. Lastly, ASTM Subcommittee D11.12 is proposing that an optional in situ cure be added as Part B to ASTM D8059 in order to also measure the Payne Effect of rubber in the cured state.