Assuring successful bonding to carton boards

Abstract

This paper considers the factors that will influence successful adhesive bonding t o carton-boards. Although the paper assumes the use of carton-board within the packaging industry, the majority of the arguments may be applied t o other bonding applications.The commonest adhesive types used within the packaging industry for carton-boards are PVA-type emulsion and hot-melts. Other adhesives used will include animal glues, starches and dextrines, acrylics etc. Although these adhesives vary considerably in properties they share the majority of requirements for successful bonding.The paper firstly considers bond structure and the basic modes of bond failure. It is surprising how often these are misunderstood or ignored when bonding problems occur. An inspection of the precise nature of a bond failure often suggests the cause of the problem, and at least eliminates a number of possible causes.The paper then discusses the properties required of boards, board surfaces (be they printed, varnished, coated or otherwise) and adhesives for the successful manufacture of bonds. Techniques for evaluating trial bond performance and, finally, the need for good 'housekeeping' are considered.Keywords: Adhesives; carton board; hot-melt; pro-type emulsions; bonding of paperboard BOND STRUCTURE AND BASIC MODES OF FAILUREFor the vast majority of packaging applications an adhesive bond comprises two substrates, an adhesive layer and interfaces between the adhesive and the two substrates. With emulsion, dispersion and hot-melt adhesives it is rare to find any appreciable penetration of the substrates by the adhesive.The basic modes of bond failure relate to the er, common usage does classify the one with the other. Moreover, a substrate of adequate structural strength is vital to achieve the overall strength of the item being bonded. Fibre-tear failure is generally taken as being an indication of a satisfactory bond to board. This can lead to a mis-judgement of bond performance where: structure described above as follows:(a) The fibre structure is of lower strength than the application demands; failure is not fibre tear, but the strength is nevertheless greater than the application demands; long term response to stress on the bond is (b)Cohesive failure -within the adhesive layer Adhesive failure -at the adhesive -substrate interface Substrate failure -within the substrate (c). IStrictly speaking substrate failure does not represent an adhesive bonding problem. Howevdifferent to 'short term response (i.e. creep effects occur).

Alternative Fiber-Based Paperboard Adhesion Evaluation with T- and Y-Peel Testing

“…In Figure 6, the average maximum force of the peel adhesion strength for all three paperboards is presented. The trends are similar for both Y-and T-peel testing, where the SD sample had the largest maximum value for the Y-peel (23.8 N) and somewhat lower Nevertheless, some researchers [2] claim that too high a penetration of the adhesive may cause some problems while there is too little adhesive left at the surface and the bonding is weaker than it should be. Regarding penetration dynamic analysis, where the capillary penetration is obvious for sample JK as well as for BL (the signal intensity drops instantly), the high penetration of the adhesive could be true for sample JK, which has an extremely porous structure and the penetration of the liquid occurs instantly.…”

“…Nevertheless, some researchers [2] claim that too high a penetration of the adhesive may cause some problems while there is too little adhesive left at the surface and the bonding is weaker than it should be. Regarding penetration dynamic analysis, where the capillary penetration is obvious for sample JK as well as for BL (the signal intensity drops instantly), the high penetration of the adhesive could be true for sample JK, which has an extremely porous structure and the penetration of the liquid occurs instantly.…”

“…According to Shires [2], this method can lead to misinterpretation of adhesive bond performance in scenarios where (a) the fiber structure's strength falls short of application demands; (b) failure does not involve fiber tear, yet the strength exceeds application requirements; (c) the bond's long-term response to stress differs from its short-term behavior, such as the occurrence of creep effects.…”

Finite Element Analysis of Hot Melt Adhesive Joints in Carton Board

“…Korin et al . or the discussion about bond structure in Shires) that the performance depends on the fracture mechanisms. Nevertheless, the model presented here cannot be used currently for a prediction of the bond behaviour, as the model simulation has to be stopped before peak load failure.…”

“…Shires has reported criteria for successful bonding between adhesives and carton board. Structural strength in addition to other parameters like board absorbency and temperature or moisture content together with surface properties was identified as main variables.…”