Image Number 3 for United States Patent #4768376.
A method and an apparatus for testing the adhesion between the polyethylene coating and paperboard stock of polyethylene coated paperboard stock, such stock typically used in forming milk and fruit juice cartons. A normally open ended pressure chamber is closed by clamping a piece of polyethylene coated paperboard over its open end. The coating facing the pressure chamber is cut completely through to form an opening. Air of a predetermined value is introduced into the pressure chamber. The opposite coating will form a bubble, indicating delamination, if the integrity of the adhesion between the polyethylene coating and the paperboard is poor. The air pressure at which delamination occurs is then used to quantify adhesion.