A coating applied to a packaging substrate to enable a bond to a compatible mating material during heat sealing.
Also called: heat seal lacquer; heat-activated sealing coating.
The sealing coating and its supporting substrate
No. The foil can be a supporting substrate for a coating that provides the sealing function. Coatings can also be carried on paper or polymer films. Distinguish the carrier from the functional layer; an uncoated foil cannot be assumed to seal directly to the forming web.
In a material specification, identify which side carries the seal layer and what surface it meets. A product-family label such as heat-sealable foil is incomplete without the counterpart and construction. A paper or foil substrate description also does not identify whether the intended opening behavior is peelable or push-through.
Compatibility depends on the coating chemistry, the surface it meets, the application and sealing conditions, and the intended bond. A coating selected for one counterpart is not demonstrated for another merely because both are packaging plastics.
Ask for the coating identity, substrate/partner pairing and evidence under the proposed sealing conditions. Keep coat quantity separate from chemistry and opening behavior: more of an unsuitable coating is not a compatibility solution. Technical seal compatibility also does not establish product-contact suitability for a specific supplement pack.