While wood products are esthetically pleasing, their hygroscopicity leads to dimensional changes induced by environmental variations in humidity and/or temperature. Their dimensional instability has made it difficult to provide durable coatings, adhesives and/or sealants.  Research in wood-water interactions at the macro level has improved our understanding of the wood-water relationships, but research at the subcellular level (from 1 to 100 nm) is lacking.  However, techniques able to probe the wood cell wall nanostructure often need labeling, harsh surface preparation or must be performed under vacuum.   Advanced neutron scattering techniques are ideally suited to probe changes in wood nanostructure because neutrons provide increased contrast due to their isotope sensitivity and allow for <i>in situ</i> humidity control.  Small angle neutron scattering (SANS) studies have successfully measured the moisture-induced swelling of wood nanostructure from 1 to 100nm. These SANS studies revealed that moisture-induced swelling at the cellulose elementary fibril level is a major contributor of transverse swelling in the S2 cell wall layer and, therefore, must be addressed by treatments meant to impart durability.  Likewise, contrast variation studies capable of measuring the effects of chemical modifications, such as acetylation or phenol-formaldehyde infiltration, on the wood nanostructure and its induced swelling revealed that these modifications can minimize swelling at the elementary fibril level, even though they modify the wood nanostructure differently.

Probing nanostructural changes in chemically modified wood cell walls with small angle neutron scattering

2019 Fall National Meeting

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