Canning and Fish Packaging Technology

Unit 11 - Heat Sealing

11.1.1.3.Impulse sealing
In this method both the jaws are initially cold and on closing an electric current passes for a short time through a resistance heater placed in one jaw which gets heated rapidly and the films melt together (The jaws are covered with a special film of Teflon to prevent sticking). The jaws remain closed during heating and till the seal is cooled and the seal sets. Impulse sealing is used for homogeneous thermoplastic films, e.g. polyethylene, polypropylene and for films, in which shrinkage does not take place during sealing.