Paper materials show a continuously increasing deformation under long-term loading. This time-dependent material behaviour is called creep and it can lead to a considerable shortening on the life of paper-based packages, both during transport and in storage. An even more serious problem is the fact that the paper creep is accelerated by moisture variations, a phenomenon known as mechano-sorptive creep.

 

More than a quarter of the paper produced in the world today is used for packaging purposes and, as a rule, today’s paper-based packages are over-dimensioned in order to avoid creep failure. In spite of the large production volumes and the potential for material saving if the creep of paper materials could be reduced, there are still no standardized methods for measuring the creep of paper.

 

Innventia has unique methods and equipment for measuring the creep properties of papers at different load levels in both a constant and a cyclic climate. Creep tests on liner, fluting and paperboard can be carried out under both tensile and compressive loading, the latter having been made possible by the development of a new compression tester. Our laboratory also has equipment for the creep testing of single fibres, corrugated board panels, whole packages and pallet-loads of packages.

 

These methods enable us to investigate why paper materials creep, to develop manufacturing methods which reduce the creep, and to develop models which make it possible to predict creep.