Analysis of graphene-encapsulated polymer microcapsules with superior thermal and storage stability behavior

Abstract

A new series of urea-formaldehyde polymer microcapsules with two-component cores have been synthesized by an in-situ polymerization procedure. Graphene was used as one of the components in the core material along with a bisphenol-A epoxy resin. Preparation of graphene oxide was carried out by the Staudenmaier oxidation process, followed by further thermal treatment in a controlled environment to produce thermally treated graphene (TTG). The thermal and physical properties of the microcapsules were investigated by TGA (Thermogravimetric analysis) and, SEM (Scanning electron microscopy) among other methods. The chemical composition of the microcapsules was ascertained by FTIR (Fourier-transform infrared) spectroscopy. The resultant graphene-encapsulated microcapsules have shown an increasing degree of thermal stability in the range from 250 °C to over 400 °C, depending on the TTG wt%. They also exhibited good storage stability (>90%) over different periods of time. It was determined that the thermal and physical properties of the microcapsules are closely linked to the core materials and the processing conditions. The processing conditions, in turn, can be varied to synthesize different types of microcapsules with different sizes, thermal stability and yield percentage values. The improved sway over the thermal degradation provided better control over the release rate of the core material under various conditions. Also, the unusually high thermal stability behavior of the polymer microcapsules' shell wall demonstrates better survivability of these microcapsules under harsh external conditions which can be exploited in their use as highly stable self-healing agent carrier in high-performance polymer materials.