Pressure sensitive cap seals versus heat seals: which to choose and how to store them?

Pressure sensitive cap seals versus heat seals: which to choose and how to store them?

February 2016

  • Description and use
  • Applications and types
  • How do I choose my cap seal?
  • Storage recommendations



What is a cap seal?

A seal is a thin film of aluminium, plastic or compound materials positioned on the opening of containers such as vials, bottles, jars, pill bottles or jugs in order to (depending on the type of seal):

  • provide a hermetic, watertight seal
  • provide a guarantee that the container has not been tampered with and has never been opened.
  • protect the product against light, oxygen, moisture, germs and odours

Applications and types

Cap seals are mainly used by the food, cosmetics and pharmaceutical industries. But they are also used on veterinary products, agrochemicals, automotive lubricants and household products.


  • pressure-sensitive-2Pressure sensitive seal liners: the seal, consisting of a polystyrene layer and a heat seal layer is inserted into the screw closure (cap or lid) and adheres to the lip of the container when the cap is screwed on.

Points to watch for:

=> The recommended torque must be strictly respected.

=> To ensure a good seal, drying time of at least 48 hours is required. If you need to open the cap (for instance to insert a leaflet or an accessory between the seal and the cap), you need to wait at least 48 hours.


  • InduktionsSiegeleinlagen_kleinSeal liners applied by heat: the seal, consisting of a plastic, aluminium or paper film and a heat seal layer, is sealed to the lip of the container with a heat sealing machine.

The seals can be flat or pre-formed (stamped) and are customizable.


Heat sealing is the process involved in heat sealing a seal to a compatible container. (There are two methods: conduction sealing / induction sealing). 

Before choosing my seal, I have to answer the following questions:

  • What product am I packaging?
  • How am I packaging it?
  • What is its shelf life?
  • How is it stored (refrigerated or not)?
  • Do I want to customize my cap seal?
  • What packaging am I using: container and closure (plastic, glass)?Quel produit vais-je conditionner ?

The answers will help you determine the type of seal you can use. Some examples:

=> The pressure sensitive seals can be used for:

  • food supplements in capsules or tablets (dry form)
  • spices
  • nuts

=> The heat seals can be used for:

  • spreads
  • sauces (ketchup, mayonnaise), honey
  • dairy products (yogurt, milk)
  • toothpaste
  • inks
  • technical products

=> If the seal comes into contact with foodstuffs you must check the compatibility between the seal materials and the type of food by referring to the technical and regulatory information.

=> For packaging hot products, I should use a heat seal.

=> If my product should be refrigerated, I should use a heat seal.

=> Only heat seals can be customized.

Storage recommendations

Pressure sensitive seals

  • These seals are heat-sensitive and should be stored between 15 to 20° C maximum and at a humidity between 40 and 60%.
  • The seals should be used within 90 days after receipt.
  • Once the seals have been placed in the caps, they should be used within 9 months.

Heat seals

These products are less sensitive but some storage rules must be followed:

  • Store between 15 and 35° C and humidity of between 30 and 80%
  • Store in a dry location
  • Keep away from direct sunlight
  • Do not store near heat sources
  • To ensure seal properties and quality, do not store for more than 18 months.Conserver entre 15 et 35°C à un taux d'humidité compris entre 30 et 80%


 The information in this article refers only to the types of packagings distributed by Fidel Fillaud

Recycled plastic bottles

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