Tearing Glue Joints

Will asks;

We have recently had a slew of customer concerns in regards to glue joints. Our customers are saying that it is “tearing too easily.” This is for both hot melt and soft white glued boxes, (generally larger boxes that are NOT run through a flexo folder, but rather a Bahmuller or similar piece of equipment). Is there any way to baseline what poundage a glue joint should hold? Does it depend on what liner the board has and what material it is? If so how do you recommend measuring it?

Thank you for the question. First let me point you to an AICC resource, Key Characteristics of Linerboard and Medium and Their Impact on Combined Corrugated Board.  In that brochure you will learn what linerboard physical properties impact glue joint adhesion. Have you reviewed the FBA Handbook?  There is also a TAPPI Test Method for testing adhesives used in glue lap joints.

The strength of the glue bond is dependent on board moisture, relative humidity, slide angle, fibre type, surface strength and internal bond.

The type and location of the fibre tear, rather than an actual physical property value, will provide better information for identifying the source of the issue. Do you have any pictures to share? Is this a recycled linerboard?  Do you have any Dennison wax pick strips? Do you have containerboard mill specifications from the paper suppliers?

Where I am headed is that while it may be the adhesive, the environment, the process, the amount of coverage, it is usually a board and liner issue. Can you provide more information that will help us dig further into the issue?

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