NATURAL RUBBER BOUND 4-AMINODIPHENYLAMINE ANTIOXIDANT INTO LATEX PHASE VIA EPOXIDE GROUPS TO IMPROVE THE RESILIENCE OF NATURAL RUBBER FROM OXIDATION

• Main Author: Handayani, Hani
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/34034
• Institution: Institut Teknologi Bandung

Natural rubber is one of the commodities that are very important in supporting the Indonesian economy because of their role as a source of foreign exchange from non-oil sector. However, natural rubber has some weaknesses, such as not consistent in its properties, not resistant to weather, heat, ozone, and hydrocarbon solvents. Various attempts have been made to overcome the weaknesses of natural rubber either physically or chemically, one of them is the addition of antioxidants as additives in the manufacture of rubber goods because the process is relatively easy and inexpensive. However, this has the disadvantage of mechanical technic including antioxidant blooming (migration the rubber to surface) giving failed products and decrease in antioxidants ability. The aims of this research is to improve the resilience of natural rubber from oxidation through the chemically-bound antioxidant to epoxidized latex. Fresh latex was deproteinized using 0.06 phr papain. Latex was epoxidized using formic acid of 0.3 mol/mol of isoprene units and hydrogen peroxide of 0.75 mol/mol of isoprene units at various temperatures (ranging from 60 to 80 °C), time (1-4 hours) and stirring speed (125-700 rpm). The epoxidation showed that higher temperature resulted in higher mole percent of epoxy but at temperatures above 70 °C the latex became greatly destabilized. Longer reaction time increased the epoxidation yield but the stirring speed did not significantly affect it. It was also found that high speed stirring could reduce the mass transfer and therefore, the optimum speed was chosen at 700 rpm. Then the 4-ADPA (4-aminodiphenylamine) antioxidants was added at the optimum temperature and stirring speed during a varied period from 1 to 4 hours. The mole percent of 4-ADPA was varied between 0.025 to 0.1 mol/100 grams of rubber and four variations in temperature were applied (between 27-80 °C). The results showed that the epoxidized latex obtained after 3 hours showed a relatively stable binding. The binding of antioxidant to the latex could occur at a minimal dose of antioxidant of 0.1 mol/100 grams of rubber. It was also found that the use of temperature higher than room temperature destabilized the latex, causing a latex coagulation in less than 2 hours. It was concluded that the optimum condition for the binding was at 27 °C at a dose of antioxidants as much as 0.1 mol/100 grams of rubber. Furthermore, the reaction was left for 24 hours and then coagulated with methanol and purified with soxhletation using acetone for 8 hours. The analysis of FTIR spectra revealed that the binding of 4-ADPA into the epoxidized latex was as much as 1.93 phr. The up scaling process was also done to make a vulcanized rubber for the oxidation resistance testing including tensile strength, elongation at break, modulus 100%, and hardness, before and after ageing at 90 °C for 2, 4, 6, and 7 days. The Rheometer curve analysis showed that the natural rubber bound 4-ADPA was more resistant to ageing based on the value of R300. The physical properties testing showed that the effect of the chemically-bound 4-ADPA on the tensile strength was observed when the ageing was more than 4 days. The other physical properties were not significantly affected.