IAWS PhD Prize

Abstract

Nanofibrillated cellulose (NFC) from wood is an interesting material constituent of high strength and high aspect ratio, which easily forms networks through interfibril secondary bonding including hydrogen bonds. This has been exploited in preparation of new materials, which extend the range of properties for existing cellulosic materials. The objective is to explore processing–structure and structure– property relationships in NFC materials. Dense networks of NFC referred to as ‘‘nanopaper’’ having a random-in-theplane orientation of the fibrils have been successfully prepared by a papermakinglike process involving vacuum filtration and water evaporation using laboratory papermaking equipment. Large, flat and transparent nanopaper sheets have thus been prepared in a relatively short time. Using the same preparation route, NFC was used to reinforce pulped wood fibers in dense network structures. NFC networks formed in the pore space of the wood fiber network give an interesting hierarchical structure of reduced porosity. These NFC/wood fiber biocomposites have greater strength, greater stiffness and greater strain-to-failure than reference networks of wood fibers only. In particular, the work to fracture (area under the stress–strain curve) is doubled with an NFC content of only 2 %. The papermaking preparation route was extended to prepare nanocomposites of high NFC content with a cellulose derivative matrix (hydroxyethyl cellulose, HEC) strongly associated with the NFC. Little HEC was lost during filtration. The NFC/