Constructing Out-of-plane Auxetic Response in Paper

It is known that several kinds of paper (including the common copy paper) increase in thickness when stretched. Previously, we examined several commercially available papers and found this behavior in some of them. We also devised, utilizing a few other reports, a mechanistic explanation for the origin of this auxetic response. In this research, we apply our understanding of this mechanism to construct auxetic paper handsheets. Key structural parameters of a nonwoven cellulose fiber network in paper –fiber length, sheet thickness and crosslinking density, that were previously predicted to affect the magnitude and sign of Poisson’s ratio, were altered to produce a range of handsheets. It was found that longer fibers, crosslinking density, extent of refining, and sheet thickness significantly affect the magnitude of auxetic response in paper.