Heat Seal-Induced Pinholing in Double-Coated Paperboards, 1997 Polymers, Laminations & Coatings Conference Proceedings
When polyethylene-coated paperboard cartons are heat sealed, water, trapped within the paperboard, is vaporized. If too much heat is applied, this pressurized vapor will blow through the semi-molten polyethylene coatings to form pinholes. And, in high melt index coatings, pinholes can occur before a good heat seal is achieved. Pinholing is best controlled with low melt index polyethylene coatings. The lower a coating’s melt index, the greater its resistance to heat-induced pinholing.