Synthesis, photo curing and viscoelastic properties of triacrylate compositions based on ricinoleic acid amide derived from castor oil

A novel trifunctional acrylate (CODTA) was obtained by the chemical modification of castor oil. Photo-polymerization of CODTA with varying amount of trimethylol propane triacrylate (TMPTA) or tripropylene glycol diacrylate (TPGDA) was carried out in presence of photo initiators to yield crosslinked networks. UV curing studies of all the compositions were done with photo-DSC equipment. Higher polymerization rates were observed for the copolymer compositions containing either TPGDA or TMPTA in place of pure CODTA monomer. Conversions were calculated from the heat liberated under isothermal conditions. Conversions improved with diacrylate (TPGDA) dilution whereas lower values were obtained with triacrylate (TMPTA) addition compared to pure CODTA. The pure CODTA films depicted fairly good storage modulus (6.3 × 108 Pa) and a glass transition temperature of 91 °C in the DMTA studies. Improvement in storage modulus was observed for copolymer compositions containing 10% of either TPGDA or TMPTA. Slight improvement in Tg values was observed with TPGDA dilution, whereas reduction in values was obtained with TMPTA dilution compared to CODTA. All the copolymer films exhibited β-transitions in the loss modulus plots which may be due to rotation of alkyl side groups attached to the polymer chains. The molecular weight between the cross links (Mc) of the network chains was found to depend to a great extent on the nature and content of the co monomer. Addition of TPGDA enhanced the Mc values whereas the reverse was observed with increasing TMPTA content.