Preparation of constant viscosity natural rubber with mercaptan

Constant viscosity natural rubber has been prepared using mercaptan. The accelerated storage tests indicate that the storage hardening phenomenon of natural rubber can be inhibited by mercaptan. The amount of mercaptan (2-mercaptobenzothiazole) of 0.14 phr is sufficient to prepare constant viscosity natural rubber and the storage hardening numbers of constant viscosity NR in both Mooney viscosity and Wallace plasticity are less than 4. The processing properties and anti-oxidative behavior of CV-NR can be improved, although the mechanical properties of vulcanizates decreased slightly as compared to those of natural rubber. The results further support the hypothesis that the abnormal groups in natural rubber molecules are aldehyde groups and are responsible for the hardening of natural rubber.