The non-rubber components, i.e., proteins and lipids/phospholipids, in the CNR were confrmed to be the important components which participate in the gel formation and infuence the physical properties of NR. The removal of proteins in the DPNR and WSNR affected the reduction of gel content. The decomposition of branching by SPNR was effective to remove the gel after removing free proteins and phospholipids by acetone extraction and/or polar solvent treatment. The occurrence of storage hardening was found in the CNR, DPNR and A-SPNR, showing the increase of plasticity and Mooney viscosity, after ASHT. The suppression of storage hardening phenomena in the WSNR and AE-CNR indicates that either proteins or free lipids can promote the formation of gel and result in the storage hardening. This points towards the fact that both proteins and lipids are necessary for the storage hardening in the NR. In contrary, AF-SPNR showed a lower magnitude of storage hardening as compared to A-SPNR, due to the presence of focculants that obstruct the formation of branching and gel during the storage.

The authors gratefully acknowledge Mahidol University and the Center of Excellence for Innovation in Chemistry (PERCH-CIC), Ministry of Higher Education, Science, Research and Innovation. Sincere appreciation is extended to the Thai Rubber Latex Group Public Co., Ltd. for supplying NR latex

Rojruthai P, Kantaram T, Sakdapipanich J. Impact of non rubber components on the branching structure
and the accelerated storage hardening in Hevea rubber. J. Rubber Research. 2020:23:353-364.