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Non-isocyanate polyurethane (NIPU) was synthesized from epoxidized linoleic acid (ELA) from rubber seed oil. In this study, carboxylation method was used to synthesize a new monomer, carboxylated linoleic acid (CLA) to produce urethane inter-linkage polymer. ELA with tetrabutylammonium bromide (TBABr) as catalyst was purged with carbon dioxide as gas reactant. Pressure and temperature reactions were controlled at 10 psi and 150 °C. CLA was mixed with ethylenediamine (EDA) and the viscous mixture was cured in a covered mold in an oven at 100 °C and curing was performed after 12 hours. Tacky test was done to evaluate the curing. The initial epoxy value of ELA was 7.36 % and it was observed during synthesis to reduce via Oxygen Oxirane Content test, which illustrated the conversion of ELA to CLA. The formation of epoxy group in ELA to carboxylate functional group in CLA was characterized using Fourier Transform Infrared (FTIR) at absorption peak of 1803.69 cm-1that represent cyclic carbonate group. H-NMR was used to support the characterization of ELA and CLA.

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Epoxidised rubber seed oil (ERSO) was successfully synthesized into non-isocyanate polyurethane via carboxylation method whereas peroxoformic acid was formed by in-situ reaction for epoxidation. The effects of temperature and ratio of hydrogen peroxide and formic acid to rubber seed oil carboxylation were studied. The optimum temperature for the epoxidation reaction was found at 50 °C to avoid ring opening reaction of epoxy whilst the optimum ratio of hydrogen peroxide and formic acid is equal molar of double bond: formic acid at 1:2 and 1:1, respectively. At a lower concentration of hydrogen peroxide and formic acid, the oxirane ring was stable due to the lower hydrolysis (oxirane cleavage) of an epoxide. The effect of using low content of formic acid tends to minimize unwanted epoxide ring opening to occur and make the epoxidation rate increased with increasing of oxirane number. Fourier transform infrared (FTIR) spectral displayed the presence of an epoxy functional group at 822 cm-1 and the disappearance of double bond peak at 3011 cm-1 corresponding to epoxidised oil and carbonyl group confirmed the epoxidation reaction had taken place. 1H-NMR was used to confirm the formation of carboxylate functionality after the reaction of epoxy at δ 4.83 and 4.61 ppm. In conclusion, ERSO has great potential to be used as a precursor in producing environmentally friendly non-isocyanate polyurethane.

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