The congress layer is used in concave cardboard as a corrugated layer between two layers of paper. The base weight of the middle layer is between 90 and 200 g / m2.
The congress layer gives the carton the required strength;
the most important properties of this type of paper should be rigidity and resistance to crushing and breaking. A special feature of congressional paper is its ability to pass through the conversion machine. Passability here means the sheet’s ability to withstand stresses and tensions in the congressional operation without cracking or failure. The two factors that increase the permeability of the sheet are high elasticity and being free of wood chips and fibers..This specification is created by good refining of the dough and less tension during sheet drying to optimize tensile strength in congress paper. Floating paper should have higher water absorption than liner test paper because very low water absorption prevents the adhesive from penetrating the paper. Due to the fact that flotation paper acts as a shock absorber in the carton sheet and its congressional structure must be able to distribute the forces applied to the package, so this type of paper after congress should be able to have static resistance and reversibility after the application of environmental forces.