Synthesis, photopolymerization and evaluation of electrical properties of epoxidized castor oil-based acrylates

Abstract

In this study, synthesis, characterization and photopolymerization of new type of castor oil-based monomer family are studied. Electrical properties of the synthesized polymers are also evaluated. The synthesis of these materials consists of two steps. Acrylation of the castor oil and methyl ricinoleate occur in the first step and epoxidation is then followed. Epoxidized acrylated castor oil (EACO) and epoxidized acrylated methyl ricinoleate (EAMR) are synthesized at the end of the reactions. FTIR (Fourier transform infrared) and 1H NMR (nuclear magnetic resonance) spectroscopy techniques are used to characterize of the starting materials and monomers. When acrylate groups are introduced to castor oil and methyl ricinoleate, a characteristic peak at 1722 cm−1 is observed in FTIR spectrum and peaks of acrylate hydrogens at 5.7, 6.0 and 6.3 are observed in 1H NMR spectrum. After epoxidation, a small peak is detected at 840 cm−1 in FTIR spectrum and new peaks appear at 2.5 and 3.0 ppm in 1H NMR spectrum. Photopolymerization of the synthesized materials are performed with DMPA (2,2-dimethoxy-2-phenylacetophenone) and AIBN (azobisisobutyronitrile) catalyst. It is found that DMPA catalyst is more effective than AIBN. EACO samples’ DC (direct current) resistance and conductance values are measured as 146.4 MΩm and 6.83 nS/m, respectively, whereas EAMR samples’ DC resistance and conductance values are calculated as 96 MΩm and 10.42 nS/m, respectively. AC (alternative current) analysis is conducted by using LCR meter for the polymeric samples where EACO samples’ capacitances varies from 4.88 to 3.29 pF (picofarads) with respect to frequency (10 Hz–300 kHZ). On the other hand, EAMR samples’ capacitances varies from 14.7 to 6.49 pF with respect to frequency. Impedance values of the EACO samples with respect to frequency are measured as 4.24 GΩ and 165 kΩ, respectively. Impedance values of the EAMR samples with respect to frequency are measured as 1.19 GΩ and 82 kΩ, respectively.