Synthesis and characterization of non-isocyanate polyurethane from rubber seed oil, oleic oligomer, and oleic acid as a raw material / Raden Siti Amirah Hambali

Polyurethane is a versatile material that is utilized for various applications. Conventional polyurethane is synthesized from polyols and polyisocyanates. However, the toxicity of isocyanate could cause health issues such as skin irritation and lung problems. Its toxicity is exposed during manufacturing and in the end-product. Therefore, the development of non-isocyanate polyurethane is an alternative that is environmentally safe to produce polyurethane. The non-isocyanate polyurethane is developed through chemical modification processes which involve epoxidation, carbonation and curing. During the epoxidation process, the double bond functionality of raw material was converted into an epoxide ring using peroxoformic acid generated in-situ. Carbon dioxide gas was introduced to the epoxide ring to form a cyclic carbonate ring. The cyclic carbonate ring was then reacted with ethylenediamine to yield a non-isocyanate polyurethane. The non-isocyanate polyurethane was synthesized from rubber seed oil, oleic oligomer, and oleic acid as raw material of different functionality numbers of F≥3, F=2, and F=1, respectively. Rubber seed oil was extracted using hexane via solvent extraction method in 7 hours. The extracted rubber seed oil’s properties of viscosity, iodine value, acid value, and FFA were found at 35 mPa/s, 192.89 gI2/100g, 25.5 mgKOH/100g, and 12.81 %, respectively. The oleic oligomer was synthesized from oleic acid and ethylene glycol. The optimum ratio of ethylene glycol to oleic acid for the oligomer conversion was found at 1.5:1. The oleic oligomer had iodine value, acid value, and FFA of 94 gI2/100g, 7.21 mgKOH/100g, and 3.62 %, respectively. The reaction temperature and the ratio of hydrogen peroxide and formic acid to the double bond of oil were the parameters being investigated in epoxidation process. The optimum epoxidation condition to yield maximum epoxide conversion was found at 50 ℃ and the reactant ratio of 1:1:2 (oil : formic acid : hydrogen peroxide). The epoxide conversion of 73 % after 4.5 hours for epoxidized rubber seed oil, 63 % after 3 hoursfor epoxidized oleic oligomer, and 91 % after 3 hours for epoxidized oleic acid were achieved under the optimum parameter settings. The epoxidized oil then underwent a low-pressure carbonation process. The cyclic carbonate conversion was increased rapidly in the initial stage of the cyclic carbonated rubber seed oil and a gradual conversion for the cyclic carbonated oleic oligomer. The cyclic carbonated oleic acid conversion from epoxidized oleic acid was unsuccessful due to self-attack during the carbonation process where the carboxylic acid group of epoxidized oleic acid will attack its opened epoxide ring. The non-isocyanate polyurethane film was formed by curing the cyclic carbonated oil with ethylenediamine. The optimum percentage of ethylenediamine was found at 20 %. Pencil hardness test on the film resulted in hardness ranging from 2B to 4H for non-isocyanate polyurethane derived from rubber seed oil and 5B to 2H for oleic oligomer. The tensile strength and elongation percentage for non-isocyanate polyurethane derived from rubber seed oil were found at a range of 20 kg/cm2–35 kg/cm2 and 20 %-85 %, respectively. While 5 kg/cm2–25 kg/cm2 tensile and 28 %-75 % elongation for oleic oligomer. Thus, the non isocyanate polyurethane derived from rubber seed oil had higher hardness, tensile strength, and elongation percentage compared to oleic oligomer as raw material. The degradation temperature of the non-isocyanate polyurethane was found at 224 °C.