Controlled in situ Nanocavitation in Polymeric Materials
Yajun Cheng, Joseph M. Antonucci, Steven Hudson, Nancy Lin, Xinran Zhang, Sheng Lin-Gibson
A new strategy to produce polymer-inorganic composites with ultra low volume shrinkage has been developed. Small amount of cavitation agent, acetone dicarboxylic acid (ADCA), was introduced into acrylate-glass composites and decomposed in situ to carbon dioxide and acetone, by the heat generated by photopolymerization of the acrylate monomers. The gaseous carbon dioxide could induce the formation of voids inside the composites to counteract the volume shrinkage due to polymerization. The shrinkage reduction measured by dilatometry indicated that by introducing only 0.5 % (mass fraction) of ADCA in the composites the volume shrinkage was reduced significantly from 1.94 % to almost zero. Three point bending measurement showed that the voids inside the composites did not deteriorate the mechanical properties of the composites. Imaging techniques including X-ray microcomputed tomography (CT), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the voids inside the composites, which suggested the size of the voids was in the nanometer scale.