Natural rubber (NR), a long-chain hydrocarbon polymer mostly consisting of cis-1,4-polyisoprene units, has a high molecular weight (MW) and viscosity, enabling it to show excellent physical properties. However, NR has no reactive functional group, making it difficult to react with other molecules, especially in manufacturing processes. The functionalized low-molecular-weight NR (FLNR) is a requirement to disperse ingredients into the rubber adequately. Here, the FLNR was prepared by a photochemical degradation process under UVC-irradiation in the presence of H2O2 using P25-titanium oxide (TiO2 ) powder as a photocatalyst. The optimum condition for the preparation of FLNR was the use of 2.0 g of TiO2 powder per 100 g of rubber and H2O2 at 20% w/w under UVC-irradiation for 5 h. The hydroxyl groups were found on the NR chains due to the chain-scission of polyisoprene chains and hydroxyl radicals in the system. The weight average MW of NR decreased from 12.6 × 105 to 0.6 × 105 gmol−1, while the number average MW decreased from 3.3 × 105 to 0.1 × 105 gmol−1.

The research project was funded by Thailand Science Research and Innovation (former Thailand Research Fund), the National Research Council of Thailand (NRCT) and Mahidol University. The authors also 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 the NR latex.

Nijpanich S, Nimpaiboon A, Rojruthai P, Sakdapipanich J. Hydroxyl-Terminated Saponified Natural Rubber
Based on the H2O2/P25-TiO2 Powder/UVC-Irradiation System. J. Polymers. 2021:13(8):1339.