Child Proof Cap: How to achieve a perfect seal every time?

Child Proof Cap

Products that are perfectly sealed provide consumer confidence in their quality and safety.

Manufacturers know that a poor quality seal on their products not only threatens consumer perception of their company and products, but also results in product loss and damage in transit.

Understanding how to identify and control induction sealing variables helps to achieve a perfect seal (such as child proof cap).

The process of developing a perfect sealing solution includes matching conditions between the lid, liner and sealer; setting an operating window; and establishing the testing method to identify a good seal.

Material Compatibility

A perfect seal can be achieved with any type of container.

The choice of the appropriate induction seal depends on the product to be packaged. 

If the product contains any volatile or potentially aggressive ingredients, chemicals, acids, solvents, high sodium content, alcohol or vinegar, a seal with a protective layer or barrier may be necessary and can be placed between the film being heated to seal and the foil to prevent corrosion.

The liner is the next consideration. One type of child proof cap is a one-piece liner, which has a backing commonly made of cardboard, foam or a layer of paper. When induction is performed the entire structure is sealed to the mouth of the container with nothing left in the lid.

This type of liner is typically used for food, beverages and vitamins or for products that do not require another seal on the lid to seal the product once the foil has been removed.

Another classification is the two-piece liner. This is a two-piece wax-bonded material, which has a backing usually of cardboard or foam bonded to the aluminum with wax. 

During the induction process the wax is heated, melts and is absorbed by the backing, which remains inside the lid and allows the product to be sealed when the container is closed once the aluminum has been removed. 

When working with aggressive or volatile products, a barrier layer can be included to act as a barrier between the heat-sealing layer and the foil.

There is also a two-piece seal that combines a higher containment barrier and the foil seal. The backing of this seal has a polyester foil in order to provide better oxygen permeability and better vapor or moisture transmission once the seal has been removed.

Finally, the removal characteristics of the seal must be determined. Does your application require a child proof cap that does not leave any residue in the mouth of the container when removed?