For the purpose of this article, peelability will be defined as the ability to separate two materials in the course of opening a package without compromising the integrity of either of the two. In packaging, a peelable system provides a controlled, reliable, aseptic means of opening a package and presenting a product. The sealant layer of one or both webs is responsible for bonding the two materials together, which is accomplished via the application of heat.
The force required to pull a seal apart is called its “seal strength”. Seal strength in a peelable system is controlled by the composition of either the heat seal coating or the sealant layer. Peelable films are generally based on polybutylene-polyolefin technology. The incompatibility of the two polymers inhibits the sealant layer from forming a complete bond by reducing the number of available bonding sites. These peelable systems provide seal transfer by internal cohesive splitting between the polyethylene and polybutylene layers because of poor interfacial adhesion, which reduces internal bond strength.