To meet the environmental challenges,the use of plastic packaging must be drastically reduced.Paper-based solutions may be a credible alternative provided that their production cost is reduced.One way may be to improve the paper stiffness to weight ratio.In this work,a simple and low-cost approach is proposed,which consists in printing a patterned grid of starch at the paper surface by using a widespread printing process.With only a small quantity of starch(7 g/m~2),the bending stiffness of a packaging paper of 60 g/m~2 is multiplied by more than a factor three.This improvement originates from the permanent 3D shape the paper unexpectedly takes after printing.The printed lines form"valleys"whereas the unprinted zones are raised,forming"mountains".Drying shrinkage of the starch is assumed to play a major role,in particular by inducing local buckling of the unprinted zones.In addition,the resulting 3D shape can be interestingly tuned by adjusting the grid pattern.Even if a better understanding is necessary to be able to well control the phenomena,this approach appears relevant to form"architectured"papers with improved bending resistance to weight ratio.
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