What is a non-substrate?

Answer 1

a substrate that is not porous. IE has no pores. But more importantly it is impervious to water or air. In a material this would mean that an adhesive would need to either melt/weld or create a bond between it and the substrate. A water based glue for example would want to penetrate the surface of a substrate to create a surface it can bond to. A non-porous substrate would not allow this and so the bond, if an, would be weak.