Heat seal lacquers are useful coatings for lidding and other end-uses where a flexible substrate is coated at one location, stored, transported, or otherwise processed, and sealed to another surface at a later time with heat and pressure. Having a coating over the entire surface allows the converter some leeway in registration in the heat sealing process in end-uses like lidding, or the ability to seal over a large area for blister-packs. In addition, a substrate with a thin, liquid-applied coating can be recyclable, an advantage over polyethylene-laminated heat seal substrates.
Heat seal lacquer materials are tailored for the type of substrates being sealed together and contents of the package. Both polymer properties and formulation variables can be chosen to target bond strength, activation temperature, and bond failure mode, all being optimized for a given end use. This paper will discuss the effects of different polymer compositions and particle structures as well as formulation variables on the material properties and end-use performance in a heat seal lacquer.