(105a) Development of Resorcinol Formaldehyde Aerogels with Enhanced Mechanical Properties Via Improved Particle Necking

A new highly porous resorcinol-formaldehyde (RF) aerogel with improved particle necking is presented in this work. This RF aerogel is developed under CO₂ supercriticaldrying conditions without any structural shrinkage. The water content and the catalyst percentage are varied to modify the solution’s initial pH value and enhance particles connections. Firstly, the water content is fixed while the catalyst percentage increases in the solution to modify particles number and size. The number of particles increases with the catalyst content, and this generates a fine pearl necklace configuration with point-to-point connections that have brittle characteristics and a very low total thermal conductivity of 24.8 mW/m.K. The solid conductivity in this configuration is reduced at a high catalyst concentration due to the increased interface resistance and the reduced solid path. As the water content increases in the solution, the solution shifts towards the acidic region, and the chance to form a network decreases due to the increased void fraction. But as the catalyst percentage increases, the solution’ pH value shifts towards the basic, and the particle number increases, resulting in strong particle-to-particle connections. This transforms the particle-to-particle point connections to neck connections (termed to be a semi-fibril-like structure in this paper) with a similar thermal conductivity (24.6 mW/m.K) as the pearl necklace configuration. The semi-fibril-like structural elasticity is improved substantially due to the neck formation between the particles. The study concluded that at high catalyst concentration the structure thermal conductivity is fixed while its elasticity is improved with the semi-fibril-like structural.