Mechanical properties of isocyanate crosslinked resorcinol formaldehyde aerogels

In this study, in order to improve the mechanical properties of resorcinol-formaldehyde (RF) aerogel, synthesis of crosslinked aerogel using hexamethylene diisocyanate (HDI) as a crosslinking agent was investigated. The crosslinking was performed using exitu and in situ methods at two different concentrations of catalyst. The effects of the crosslinking and the catalyst concentration on the morphology and the mechanical properties of RF aerogels were evaluated by different analyzes. The Fourier Transform Infrared Spectroscopy (FTIR) confirmed the reaction of HDI isocyanate groups with resorcinol hydroxyl groups. The Scanning Electron Microscope (SEM) and Atomic Force Microscopy (AFM) results indicated changes in the morphology and thickening of the necks. For the crosslinked aerogels, compared to the native samples, a decrease of the compressive modulus and about five times increase in the compressive stress were obtained. Moreover, an improvement of the impact strength and a reduction in the hardness were observed.