Lightweight Foams and Aerogels of Biobased Nanofibers

Abstract

Biobased nanofibers are from abundant natural resources, and present interesting properties such as high strength, high aspect ratio and surface area, and ability to form networks through interfibril interactions. This makes them attractive for preparation of high porosity cellular foams and fibrillar aerogels. This could be achieved by drying aqueous nanofiber suspensions while maintaining a high porosity. In this chapter, the processing–structure–property relationship in highly porous biobased materials (mainly from cellulose and chitin) is discussed. Using freeze drying, nanofiber foams with an ice-templated cellular structure may be obtained and these have pores above the micrometer and a relatively low surface area. Other drying methods of nanofiber suspensions such as tert-butanol freeze drying and supercritical drying give high surface area aerogels with a fibrillar structure. The material structure in turn influences its mechanical properties. At a similar porosity, high surface area materials present weaker interfibril interactions and a softer and more ductile behavior. The present materials permit property tailoring after functionalization and this considerably increases the range of properties and applications for porous materials.