Diol spiroorthocarbonates as antishrinkage additives for the cationic photopolymerization of bisphenol-A-diglycidyl ether

A facile synthesis of isomeric dihydroxyl spiroorthocarbonates (SOC-DIOL) and a hydroxyl hemi-spiroorthocarbonate (SOC-OL) is reported. The SOC-OL displayed a plasticization effect when compounded with an epoxy resin derived from bisphenol-A resulting in a decrease of Tg. The analysis of volume change revealed that the SOC-OL reduced by 78% the level of shrinkage in comparison with the polymer where this additive was not added. The SOC-DIOL was even more effective than SOC-OL as antishrinking additive above a content of 20 wt.% in the photocurable formulation, inducing a 13% of expansion when 30 wt.% was used, with no detriment of the mechanical properties.