Nils Hallbäck

Y-peel characterization of adhesively-bonded carton board: an objective method

Carton board packages are often closed with an adhesive. The adhesive joint thus formed has to meet the demands during the entire product life from converting to end-use. The adhesive joint has to be characterized if it is good or bad for the actual application. Today such characterization is done by manually peeling the joint, immediately after the adhesive application in the gluing machine. The manual peel test is a subjective test that is operator dependent. An operator needs long experience to be able to perform a manual peel test. Therefore, the packaging industry is interested in a test method that can objectively predict good or bad adhesive joints. The adhesive joints have been tested in the so-called Y-peel test arrangement. An advantage of the Y-peel test is that it gives an objective result from the force–elongation curve. Testing has been performed with carton boards of two different thicknesses. Hotmelt adhesive was used and the open time was varied in the glue applicator. It was found that the Y-peel test gives results in qualitative agreement with the manual peel test. Moreover, by evaluating the energy consumption (dissipative energy) during the Y-peel test it was possible to obtain not only a qualitative but also a quantitative assessment of the adhesive joint.

Failure Modes in Adhesively Bonded Carton Boards

Carton board packages are often adhesively bonded. The adhesive joint may fail due to cohesive fracture in the adhesive, interfacial fracture between the adhesive and one of the carton board surfaces, or cohesive fracture in the carton board. The failure may also be a combination of these failure modes. From previous studies, it is well known that the failure mechanism greatly impacts the integrity and mechanical behaviour of adhesive joints. To explore these matters, detailed experiments on adhesively bonded carton boards were performed using the Y-peel setup. By monitoring the joint at high magnification with a digital video camera during progressive loading, it was possible to link the mechanical behaviour of the adhesive joint to the fracture mechanisms involved in each case. It was found that the adhesive joint failures could be categorised into four main failure modes. The two (modes M1 and M2) failure modes with low toughness, i.e., low dissipative energy, failed by interfacial fracture with small permanent deformation in the adhesive and in the carton board. High dissipative energy modes (modes M3 and M4), however, involved multiple failures and final failure by delamination or tearing of the outermost carton board ply. It was found that the Y-peel equipment could be used as a tool to develop carton boards and hot melt adhesives in order to optimise the adhesive joint for certain package applications. From the force–elongation curve characteristics, it is possible to perceive when and how the adhesive joint may fail in a real package application.

On material characterization of paper coating materials by microindentation testing

Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically. The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts are made to account for the influence from plasticity as well as from boundary effects.

Development and evaluation of a high-speed creping simulator for tissue

An innovative creping simulator for tissue has been developed to meet the requirements set by both industrial needs, such as speed and process step duration, and research ambitions, such as flexibi ...

Influence of Surface Treatments on the Mechanical Strength of Hotmelt Adhesive Joints Made of Cartonboards

Abstract The influence of surface treatments including pigment coating, surface sizing and calendering on the mechanical strength of hotmelt adhesive joints in pilot made cartonboards was studied. The mechanical strength of the joints was investigated using the Y-peel test device at 23°C and 50% relative humidity. Some of the samples were investigated with respect to the failure mode by scanning electron microscopy. The surfaces were characterized in terms of surface roughness, surface chemical composition, and adhesion behaviour. A strong adhesive bond displayed fibre tear. In addition to fibre tear, interfacial failure, i.e., failure between the cartonboard and the adhesive, was the main reason for fracture in the bonded assembly. The most important factor controlling the integrity of adhesive joints seemed to be the real contact area. The adhesive joints showed significantly higher strength when the hotmelt adhesive was first applied onto the rougher cartonboard of the assembly and then the smoother cartonboard was pressed on the adhesive than vice versa. The surface roughness of cartonboards mainly depended on whether the surface was pigment coated or not. Calendering displayed only a minor effect. No clear influence of surface chemical composition of the cartonboards on the adhesive joint strength was found due to the fact that changes in surface chemistry in this study also led to changes in surface roughness. The strongest adhesive joint was created between two medium-rough and surface-sized cartonboards.