Fig. 3

SEM images showing a air pocket in the gypsum matrix and needle-like structure of gypsite crystals and matrix–fiber interface in (b) office paper–gypsum sample, c newspaper–gypsum sample, b magazine paper–gypsum sample, e corrugated board paper–gypsum sample, f corrugated paperboard–gypsum sample, g Tetra Pak I–gypsum sample, h Tetra Pak II–gypsum sample