Scope:

ASTM D6814 is applicable for rubber compounders to estimate the extent of devulcanization because a rubber might have experienced recycling. This test method permits the compounder to determine if more curing agents are needed during the mixing of devulcanized rubber when used as a replacement or stand-alone.

Procedure:

During ASTM D6814, the crumb rubber sample is extracted in hot acetone and dried in a forced-ventilating air oven. The dried crumb rubber is swollen in a solvent with reagent grade purity. The solvent is replaced with fresh solvent multiple times during the swelling process. After that, the solvent is removed quickly from the surface of the swollen crumb rubber. The weight of the swollen sample is to be measured after drying, Cooled to room temperature, and weighed. The density of the dried crumb rubber sample is measured using methanol. Percent devulcanization is calculated using cross-linking density data of devulcanized crumb rubber.

Video 01: Cross Linking

Data:

For the ASTM D6814 test, calculate the density of dry crumb rubber using the equation given below.

Density at 23± 2 °C in g/cm³ = 0.7913 × A_l (A – B) 

Result:

In this way, the percent devulcanization is calculated using cross-linking density data of devulcanized crumb rubber.

Conclusion:

ASTM D6814 is applicable for rubber compounders to estimate the extent of devulcanization because a rubber might have experienced recycling.