tailieunhanh - Effect of some experimental factors on preparation of liquid natural rubber

The article presents a study of effect of factors such as the types of irradiation, the concentration of NR solution and the content of hydrogen peroxide in mixture on photochemical depolymerization of natural rubber. The results showed that the ultraviolet irradiation from the vapor mercury lamps (HSW-250W and HSW-125W) caused the faster rate of depolymerization than the light from HF-500W. | Journal of Science and Technology 54 (4) (2016) 563-569 DOI: EFFECT OF SOME EXPERIMENTAL FACTORS ON PREPARATION OF LIQUID NATURAL RUBBER Doan Minh Khai*, Phan Duc Nhan Military Technical Academy, 236-Hoang Quoc Viet, Hanoi * Email: khaihv@ Received: 20 November 2015; Accepted for publication: 18 July 2016 ABSTRACT The article presents a study of effect of factors such as the types of irradiation, the concentration of NR solution and the content of hydrogen peroxide in mixture on photochemical depolymerization of natural rubber. The results showed that the ultraviolet irradiation from the vapor mercury lamps (HSW-250W and HSW-125W) caused the faster rate of depolymerization than the light from HF-500W; increasing concentration of NR in toluene leaded to decrease the rate of depolymerization; and as the content of hydrogen peroxide increased the rate of depolymerization was faster. Additionally, the IR spectra, 13C-NMR of products were recorded and showed that the cis-1,4-isoprene structure has not been changed and there was the presence of hydroxyl-terminated groups in chains. Keywords: liquid natural rubber, photochemical method, molecular weight. 1. INTRODUCTION Natural rubber (NR) mainly consists of cis-1,4-polyisoprene which is more than 92 % in weight of NR [1]. Average molecular weight ( M ) of NR is from several hundred thousand to about million. In this case, it cannot be used for polymer composites which either contain the power-intensive fillers or are formed by casting as a fuel-binder for solid rocket propellants. For this purpose, it is necessary to strongly decrease molecular weight of NR to below 50,000 [2]. Liquid natural rubber (LNR) can be synthesized by many methods including mechanic impact, thermal degradation, redox and photochemical method etc [1-8]. By those methods, the molecular weight of the LNRs was from 2,000 to 50,000. When the depolymerization of NR by mechanic impact and thermal degradation, .