Hot Tack and Heat Sealing Properties of EVOH, 1992 Polymers, Laminations & Coatings Conference Proceedings

Ethylene vinyl alcoholcopolymer (EVOH) has traditionally been used as an oxygen barrier layer in the interior of multi-layer structures. A recent study compared the organoleptic properties of polyethylene and EVOH surface layers. Adsorption of d-limonene was significantly reduced in containers containing EVOH as the surface layer. The recognition of less flavor scalping loss from orangejuices prompted severalmanufacturers to use EVOH as the food contact layer for their products.

The use of EVOH as a food contact layer means EVOH will be on the surface of a piece of flexible film or coated paperboard. The surface of a plastic package must be able to be heat sealed. Hence, the hot tack and heat sealing properties of EVOH will be of interest to the user because they relate to seal integrity of the packageas well as the packaging line speed.

This report summarizes the measurement of hot tack and heat sealing properties of five EVOH resins with different levels of ethylene content and melt indexes. A Packforsk automated testing device was used for measuring the hot-tack properties. A Sentinel heat sealer was used for sealing. The effect of various equipment parameters on the hot-tack and heat sealing were delineated. An attempt was also made to compare the heat sealing data with that obtained from the automated hot tack tester by selecting an extremely long delay time.