Synthesis of a novel highly hindered spiroorthocarbonate and the study of its efficiency to eliminate the shrinkage in the photopolymerization of an epoxycycloaliphatic resin

This work involved the synthesis of a highly bulky spiroorthocarbonate with the aim of reducing or eliminating the shrinkage produced in the cationic polymerization of an epoxy resin. The dicyclododecanyl spiroorthocarbonate SOC CD was prepared in five stages. A cyclododecanyl epoxy-ester, was first prepared using cyclododecanone as the starting material. Then, this compound was hydrolyzed to the corresponding carboxylic acid. This acid was decarboxylated to produce a cyclododecanyl aldehyde that was then reacted with formaldehyde in basic solution to obtain the cyclododecane 1,1-diyl dimethanol. The desired SOC CD compound was finally obtained by transesterification of the diol with tetraethylorthocarbonate. Then, SOC CD was added as an antishrinking additive to the 3,4-epoxycyclohexylmethyl-3′, 4′-epoxycyclohexancarboxylate resin. It was found that the presence of this compound did not influence the photopolymerization rate, but it increased the level of conversion when added at 8 mol %. The volume change study revealed that by adding a concentration as low as 4 mol % of SOC CD, shrinkage was completely suppressed obtaining a volumetric expansion of 0.68 %. Upon increasing the concentration of the additive to 8 mol % the expansion increased to 3.39 %.