Abstract
Natural rubber (NR) latex epoxidation is a chemical modifcation of natural rubber to produce natural rubber with higher polarity (oil resistant) which is commonly called epoxidized natural rubber (ENR). ENR is produced from the reaction of natural rubber latex with performic acid. Performic acid is formed from in situ reaction between formic acid and hydrogen peroxide. During epoxidation process, the carboxyl group of natural rubber is converted into epoxy group and various side reaction products such as carbonyl, hydroxyl, and hydro furan. These side products must be minimalized to optimize the epoxy level. The epoxidation reaction was carried out at 70 ° C for 6 hours using 2 types of latex: fresh latex (FL) and concentrated latex (CL). The addition of reactant was varied in two ways: dropwise (coded “1”) and poured all at once (coded “2”). The epoxy product and rate constant (k) were analyzed to obtain optimum reaction condition. The epoxy and side reaction content were determined by Attenuated Resonance Fourier Transform Infrared (ATR-FTIR). The slope of epoxy-time plotting curve was determined as ENR rate constant (k). The optimum NR epoxidation reaction was achieved in CL2, which exhibited lowest value of side reaction and highest value of k (2.8082x10 -5 L mol -1 sec -1 ).
Highlights
Natural rubber (NR) is a widely applied material because it has an excellent elasticity on high tensile strength, tear strength, and modulus
The resulted material is well-known as epoxidized natural rubber (ENR) which has higher polarity, lower resilience, better rubber filler interaction, and mechanical properties (Rohadi et al, 2014; Tanrattanakul et al, 2003)
Several articles published the utilization of ENR in high specified rubber products such as oil spill recovery (Venkatanarasimhan & Raghavachari, 2013), bitumen (Al-Mansob et al, 2014), and tire tread compounds (Kaewsakul et al, 2013)
Summary
Natural rubber (NR) is a widely applied material because it has an excellent elasticity on high tensile strength, tear strength, and modulus It has low thermal, oxidative, and nonpolar solvent resistance due to high unsaturation (cis-1,4-polyisoprene) structure. Another study conducted by Roy et al (1990) exhibited that the epoxidation reaction determined second order kinetics wherein excess acid was medium. Those studies were performed in solid rubber and only few studies that discussed the epoxidation in the latex form with reagent addition technique. The highest k value was determined as optimum reaction condition
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