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How is Seal Quality Assured in Flexible Packaging?


If we talk about consumer goods, packing plays a lead role in the promotion of a product. From launching portable and pocket size packings to re-sealable packs to neon packs, all these gimmicks are getting really popular these days. And consumers won’t hesitate in paying for fancy packings. Apart from attracting buyers and disseminating information about the product, the prime job of a packing is to deliver the content safely to the intended buyer. Here, seal plays a crucial role, neither too complicated to unlock nor too easy. The seal should be strong enough only to be opened by intended user. Say pet food, the flex pack of dog food should not be delicate enough to be opened by a child or seal should not tear apart if the packet falls from a height.

How to check the seal integrity of flex pack?

Hot seal testing – The most common method used is hot sealing. Once the heat is applied, the packet has given enough time to cool down and strengthen the bond. But what about the leakage during the time when the seal is hot? The seal is less strong when it is hot. It takes a few second to cool, during that period the vacuum created inside the packet may leak and allow the microorganisms to enter inside the packing. Hot tack tester checks the strength of the seal when it is hot, to avoid such situations. This machine has a sealer and desealer to check the strength immediately. As soon the packing comes out of sealer, it enters into a desealing unit, the tension applied will be displayed on the screen.

Perforation strength – Right perforation is very important. If this strength is too high, it would be difficult to separate the packet from the point of perforation, instead, tear the other packets in the chain. The force that is required to tear a packet from point of perforation is evaluated in this test.

Vacuum leak test – Apart from testing the seal with hot tack tester, it is very important to evaluate the seal integrity with vacuum leak tester. Say, you have a heat sealer for sealing the packs. How would you check if it is making leak-proof seals? For that matter, a sealed test sample is kept inside the kit. A predefined vacuum is created inside the kit. The packets will inflate at first. When the vacuum is released, the packet will start deflating. A perfect packet will regain its original size and shape while a leaked seal packet will collapse.