The effect of hydroxylamine sulfate on the storage hardening of natural rubber

Abstract

Natural rubber (NR) consists of rubber and non-rubber components, which is mostly cis-1, 4-polyisoprene. The main non-rubber components are proteins and phospholipids which are attached at each end of the NR chains. If we store NR for prolong period, the proteins and phospholipids promote formation of a NR network. This causes the gel formation with increasing the Mooney viscosity of NR, and this is called storage hardening. The objective of this work is to study the effect of hydroxylamine sulfate on the storage hardening of natural rubber. Three types of natural rubber sample were prepared: pure NR, NR with 0.2 phr of hydroxylamine sulfate, and NR with 2.0 phr of hydroxylamine sulfate. Samples were characterized immediately (time 0) and after 12 weeks of storage at room temperature. We found that gel content and Mooney viscosity of NR without hydroxylamine sulfate are increased with the storage hardening for 12 weeks. However, both NR samples with hydroxylamine sulfate represent constant viscosity values because hydroxylamine sulfate inhibits the network and gel formation in NR. This is important as the stabilization of NR properties in the function of time is required by rubber industry.