Thermal superinsulating silica aerogels reinforced with short man-made cellulose fibers

Short man-made cellulose fibers (TENCEL® fibers) were used to mechanically reinforce thermal superinsulating silica aerogels. The aerogels were prepared via two drying techniques: ambient pressure drying and with supercritical CO2, in both cases resulting in monolithic non-brittle materials. The influence of fiber length and concentration on the thermal conductivity and flexural properties of both types of composite aerogels was evaluated. Thermal conductivity in room conditions varied from 0.015 to 0.018 W/m K; it slightly increased with fiber concentration but remained in superinsulation domain. The importance of fiber percolation concentration for synthesizing monolithic ambient pressure dried composite aerogels was demonstrated. Contrary to neat silica aerogels, non-brittle behavior was observed for composite aerogels regardless of the drying method when reinforced with cellulose fibers. Macroscopic short cellulose based fibers are efficient and easy to use for preparing robust, monolithic, thermal superinsulating aerogel materials.