In converting processes (e.g. printing, laminating, corrugating), paper materials are often exposed to tensile and shear loading in the thickness direction. Under such loads, there is a risk that the paper will suffer delamination, i.e. it will be damaged or break in the thickness direction.

 

Controlled delamination

Delamination can also arise in paper products in the end-use stage, such as in lap-joints subjected to tension and during the opening of packages. A controlled delamination can be desirable in certain cases. In the creasing of board, for example, delamination is desired in order to facilitate and improve the result of the subsequent folding operation.

 

It is important to be able to measure the mechanical behaviour of paper materials in the thickness direction (z-direction properties), since the information obtained makes it possible to improve both the converting processes and the properties of the final products. Innventia has developed unique methods for measuring the z-direction properties under both tensile and shear loading.

 

These methods make it possible to rank commercial papers and to evaluate the influence of different process parameters on the z-direction properties of the paper material, and thus to develop strategies to systematically improve the z-direction properties.