Packaging lines check hot melt carton seals by pulling the flaps apart and estimating the percentage of the glue line covered in torn board fibers. High fiber tear means a sound bond; a clean glue bead lifting off the board means poor wetting, often from cold glue, long open time or a coated board. Woodworkers read wood fiber on a failed joint the same way.
Pulled six cases off the line, all full fiber tear, the hot melt is fine. Check the compression section instead.
Also heard as
- fibre tear
- percent fiber tear
Related terms
Substrate failure
A joint failure where the bonded material itself breaks before the adhesive or the interface gives.
Hot melt
A solid thermoplastic adhesive melted in a tank or gun, dispensed hot and set within seconds as it cools.
Open time
The longest gap allowed between applying adhesive and closing the joint while it can still wet the second part.
Cohesive failure
A break that runs through the adhesive itself, leaving adhesive on both parts.