Industry Definitions - Packserv Australia

The packaging industry is laden with jargon. Here we try and help you wrap your head around it.
Induction Sealing... what is it?

Induction sealing is a non-contact heating process that accomplishes the hermetic sealing of a container with a closure that includes a heat-sealable foil laminate. The typical induction inner seal begins as a multi-laminate liner inside a closure made up of the following layers:

  • A layer of pulpboard
  • A layer of wax
  • Aluminium foil
  • A layer of polymer

The layer of polymer is compatible with the container material and capable of heat sealing to the lip of the container.

When the closure is placed onto the container and is passed through an electromagnetic field produced by the sealing head, several things occur. An electromagnetic current, called an eddy current, is induced into the foil portion, resulting in a resistance-type heating effect. The heated foil melts the wax layer, which is absorbed into the pulpboard, releasing the foil from the pulpboard, and the polymer coating melts, hermetically sealing the foil to the lip of the container.

When the closure is opened (released) the inner seal is welded to the lip of the container, and the pulpboard remains on the inner side of the closure. High speeds can be obtained using this process making it well suited for high capacity production lines.

Single Piece Foils

Unlike the previously mentioned foil with pulpboard backing, the liner is laminated with a foam or paper backing. When the liner is heated causing the polymer to adhere to the container, the entire liner with backing is attached to the mouth of the container. There is no separation of components when the cap is removed.

Lining Material & Tamper Evidence

Depending on the inner seal material used, this seal can meet the FDA requirements for "tamper evident" packaging or the seal can provide leakage protection and shelf life extension, often referred to as a "freshness seal". Many varieties of inner seal materials have been developed and are available.

Your Chuck Liner And You

A Chuck Liner is a soft material, usually made of urethane or white rubber, which is inserted within a chuck. The chuck with inserted liner is attached to the capping machine. The liner grips the cap during the capping process.

The grip generated by the liner is what allows the capping machine to tighten a cap onto a bottle. Liners will last for a very long time but they do eventually wear out. To replace a liner, simply pull out the old liner by hand and press fit in a new one, also by hand.

The liner plays a crucial role in capping
The amount of torque a capping machine can apply to a cap is determined by the amount of grip that the liner can generate on the cap. The greater the grip, the greater the amount of torque the capping machine will be able to apply to the cap and the greater the torque repeatability you will be able to achieve.

Durometer is the international standard for measuring the hardness of rubber, plastic and other non-metallic materials. A higher durometer rating indicates a harder material.

Grip vs. Wear
There is an inverse relationship between how long a liner will last and how well it grips.
Harder liners last longer but do not grip as well as softer liners.
Softer liners generate better grip with the cap but they do not last as long as harder liners.

Urethane Liners
Provide superior gripping properties and good wear characteristics. We offer urethane liners in two main durometers, 40 durometer and 60 durometer. Our standard urethane liner, 40 durometer, is the best choice for most applications.

White Rubber Liners
Combine strong gripping power with a high tensile strength for excellent wear characteristics. We primarily offer white liners as our hardest material. A white liner is generally reserved for unusual applications or circumstances where an exceptionally hard and durable liner would be beneficial, such as applications involving highly abrasive caps.

Chutex Liners
The perfect choice for smooth caps such as metal lug caps. Made of very soft material, these liners create almost a suction cup like grip on smooth surfaces.

glossary of plastics

HDPE ( High Density Polyethylene)

  • HDPE is the most common plastic in packaging. It is found in plastic milk bottles and most shampoo bottles. Because it is used so frequently it is relatively cheap.
  • HDPE has good chemical resistance to most common products, though it is slightly porous and volatile components may pass through the container walls.
  • HDPE is commonly supplied in 2 colours, White and Natural (without pigmentation). Natural HDPE is translucent but not clear.
  • HDPE can be coloured to match any colour of the PMS book.
  • LDPE (Low Density Polyethylene)is very similar to HDPE. It is softer and more pliable.

PET (Polyethylene Triphthalate)

  • It is the most recyclable of our plastics. This is the plastic of soft drink bottles, and is marked 1 in the recycle triangle.
  • PET has the clarity of glass but does not break.
  • PET tooling is very expensive, hence there has been a limited range of product available. This is slowly changing.
  • Coloured PET can not be recycled as it will contaminate the clear product, hence there is very little coloured PET product available.
  • PET does not like acetone.
  • PET cannot be filled at a temperature greater than 75°c or it will lose its shape and collapse.

PVC (Poly Vinyl Chloride)

  • PVC has the same clarity as PET, but not the same gloss. It is very good at withstanding dilute acids, alkalis, and oils.


  • Is mainly used for jars and vials.
  • It has a very good clarity but is very brittle. If you drop a Styrene jar it will shatter into sharp splinters.
  • Styrene is suitable for most cosmetic creams or water based paints but cannot withstand Methyl Salicylate (the smelly stuff in most sports rubs) or acetone.


  • Abbreviated to PP, it is a good all round plastic which looks like HDPE, ie it is milky in its natural state.
  • PP is often used in jars because it is stiff but not brittle like Styrene.
  • PP has good chemical resistance properties but is not commonly made into bottles because of its cost.
  • Most caps are made of PP. Normally the cap material should be different to the bottle material or else the cap will bind as you put it on the container.


  • Is extremely tough, very clear and very expensive. It is not normally used for bottles because of price.

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