Multiscale Characterization of Nanocomposites Fabricated by Copulverization of Epoxy Resin and Nanoclay

Effect of nanoclay on the thermo-mechanical properties of BT250E-1 epoxy resin is investigated. Nanocomposite parts containing 0, 2 and 10wt. % of Cloisite^® 30B nanoclay are fabricated by copulverization of nanoclay with epoxy resin at −25°C. Desired amounts of solid epoxy resin and nanoclay are placed into a grinder and copulverized for 20 seconds. The resulting fine powder is then cured using an APA2000 rheometer by using the time-temperature profile provided by the resin supplier. Five disk-shaped parts for each nanoclay content are fabricated. Two rectangular samples are cut out from each disk and used for characterization of mechanical properties and microstructure. Glass transition temperature is observed to deteriorate by 5% and 10% with the addition of 2 and 10wt. % nanoclay, respectively. Three-point bending test results indicate up to 28% improvement in flexural stiffness whereas flexural strength is observed to degrade by 57% over the range of nanoclay loading. Scanning electron microscopy indicates extensive nanoclay agglomeration. In order to characterize the nanoclay cluster morphology, several scanning electron micrographs are captured at 500x magnification. Nanoclay clusters and their size distribution are then identified by digital image processing. It is found that the average cluster size is 2-fold higher at nanocomposites containing 10wt.% nanoclay compared to 2wt.%. Transmission electron microscopy indicates several nanovoids trapped in the intra-cluster regions. The existence of these voids is also verified by density measurements of the cured samples of the epoxy with and without nanoclay. The reduction observed in the flexural strength is believed to be due to these nanovoids and nanoclay agglomeration.