Epoxidized natural rubber (ENR)

Epoxidised Natural Rubber (ENR) is derived from the partial epoxidation of the natural rubber molecule, resulting in a totally new type of elastomer. The epoxide groups are randomly distributed along the natural rubber molecule

Epoxidation results in a systematic increase in the polarity and glass transition temperature; these increase are reflected in the vucanizate properties. Property changes with increasing level of epoxidation include :
an increase in damping;
a reduction in swelling in hydrocarbon oils;
a decrease in gas permeability;
an increase in silica reinforcement; improved compatibility with polar polymers like polyvinyl chloride;
reduced rolling resistance and increased wet grip.


STUDY ON CHEMICAL INTERACTION BETWEEN EPOXIDIZED NATURAL RUBBER AND CARBON BLACK USING RHEOMETER
Abstract: Epoxidized natural rubber (ENR) was prepared using in-situ performic acid epoxidation method. The level of epoxide groups was varied at approximately 10, 20, 30, 40 and 50 mole% epoxide. The ENRs will later be called as ENR-10, ENR-20, ENR-30, ENR-40 and ENR-50, respectively. Chemical interaction between ENRs and carbon blacks were determined using oscillating disk rheometer model ODR2000 at 160°C for 60 minutes. We found that minimum torque and increasing rate of torque increased with increasing level of epoxide groups and carbon black content in the blend, while the induction period decreased. Comparison between two types of carbon black, we found that N-220 exhibited higher minimum torque and increasing rate of torque than that of N-330. However, the induction period of N-220 was shorter.


Methodology: In-situ performic acid epoxidation was performed using 1.7 M of NR latex (DRC ~ 20%) set temperature at 50°C before adding non-ionic surfactant (Teric N30) at a level of 13 g/l. The mixture was stirred for 30 min before incorporating of 2.6 M hydrogen peroxide and 0.9 M formic acid. Reaction time was varied in order to gain the epoxide level at approximately 10, 20, 30, 40 and 50 mole % epoxide. The ENRs were then mixed with carbon blacks (N-220 and N-330) at the level of 20, 40 and 60 phr. The carbon black filled rubbers were tested using ODR2000.


Results, Discussion and Conclusion: Epoxidized natural rubber (ENR) was prepared using in-situ performic acid epoxidation method. The level of epoxide groups was varied at approximately 10, 20, 30, 40 and 50 mole% epoxide. Chemical interaction between ENRs and carbon blacks were determined using oscillating disk rheometer model ODR2000 at 160°C for 60 minutes. The minimum torque and increasing rate of torque increased with the level of epoxide groups in NR molecules and the c-black content. This was attributed to the chemical interaction between polar functional group in ENR (i.e., epoxide group and hydroxyl groups from ring opening reaction) and carbon black (i.e., hydroxyl and carboxylic groups). Furthermore, we found that N-220 exhibited higher minimum torque and increasing rate of torque than those of N-330 filled rubbers. This may be described as the lower polar groups at the N-220 than that of N-330. Moreover, smaller the particle size of N-220 than that of N-330 play a significant role on the chemical interaction between the two phases. .