When it comes to VFFS machines, hot tack is arguably the most important rate-constraining film factor. “Hot tack” refers to the degree of resistance towards peeling apart and can be developed by a sealant layer while it remains hot immediately after being released by sealing bars. It is notable that the hot tack of packaging films that are used extensively, such as LDPE, is relatively poor.
In comparison, the hot tack of cost-effective ethyne copolymer films like EVA is better, although of all plastic films that are used in packaging, ionomer films have the highest hot tack. In fact, several packagers do not mind paying more money to incorporate these resins into their film structures as the dollar savings achieved through these structures (which offer higher machine speeds) more than compensates for the higher cost of the film. With an increase in the weight of the contents of a package this aspect becomes increasingly significant.