CLOSURE LINERS EXPLAINED
|Foamed Polyethylene (PE) Liners
(also known as F-217)
Most of our closures are lined with foamed polyethylene (PE) liners. This is our standard liner. PE liners are composed of a soft polyethylene foam core covered on top and bottom with solid, clear polyethylene and supplied in .035" thickness. PE liners have become the industry standard due to their all-purpose compatibility, resilient, compressible seal, cleanliness (no pulp dust) and economy. PE liners have excellent chemical resistance and a low moisture transmission rate. PE liners also have good taste and odor resistance and are well suited for carbonated beverages. PE is not compatible with aromatic or aliphatic hydrocarbons, meaning: solvent based products or essential oils.
|Esterfoil (Foil) Liners
Esterfoil liners are the standard lining material we offer with our glass concentrate jars. Esterfoil liners are comprised of a polyester film that is laminated to aluminum foil and then bonded to a PE foam backing. The foil layer serves as the barrier to volatile terpenes, keeping the product from escaping by means of migrating through the liner and evaporating off. In addition to offering low transmission rates, Esterfoil liners have high chemical resistance, making them an ideal liner for concentrates. Foil liners are commonly used to package perfume. They are not recommended for use with carbonated beverages.
(also known as Teflon)
PTFE (polytetrafluoroethylene) liners are the premium lining material we offer for use with our glass concentrate jars. PTFE liners are a two-layer laminate composed of a PTFE face and a polyethylene foam backing. The PTFE face offers high chemical resistance. It is capable of resisting degradation from virtually any chemical at room temperature. The PE foam backing provides a tight, compressed seal that prevents evaporation. Due to their superior barrier properties and enhanced non-stick capabilities, PTFE liners are ideal for use with products like Sauce or Live Resin which are less viscous and tend to stick to the closure liner and jar making it extremely difficult to unscrew the closure.
|Pressure Sensitive Liners (PS-22)
Pressure Sensitive liners, known in the packaging industry as "PS22", are made of a styrene foam material coated on the down facing side with a torque activated adhesive. Pressure-sensitive inner seals adhere to plastic or glass bottles with normal application torque. The liners are supplied friction fit into closures and adhere to the bottle finish when the closure is applied. Pressure sensitive liners are coated with pockets of adhesive. When the closure is applied to the container, the pockets of adhesive rupture between the closure and finish of the bottle or jar. The pressure sensitive liners then stick to the bottle or jar and remain in place when the closure is removed. No extra equipment is required. This material needs a dry land area on the bottle and therefore is suitable only for use with dry products such as vitamins, foods and pharmaceuticals. Pressure Sensitive liners are not recommended for use with cannabis flower as the styrene material does not provide a good oxygen barrier and the product "shake" will stick to the liner.
Induction Heat Seal Liners
Induction heat seal liners are a specialty type of liner that adhere to the bottle or jar, providing an airtight seal, an extra layer of protection against leakage as well as functioning as a tamper evident barrier.
The main benefits of induction heat seal liners include:
- Hermetic seal: The foil liner is welded to the container creating a permanent, airtight bond with an impermeable foil layer.
- Tamper evident seal: Available as Clean Peel or Welded Seal.
- Ability to Automate: Equipment can be placed over a conveyor belt allowing the sealing process to occur with no additional labor cost.
- Relatively inexpensive.
- Compatible with liquid or dry products.
How It Works
Induction sealing is a non-contact process that creates a hermetic seal by means of a heat-sealable foil laminate. The induction inner seal is an aluminum foil liner with a layer of polymer on the side facing the container. In order for the seal to function properly, the layer of polymer must be compatible with the particular type of plastic or glass container. To begin the sealing process, the closure is placed onto the container and passed through an electromagnetic field produced by the sealing head. An electromagnetic current, called an eddy current, is induced into the foil layer, resulting in a resistance-type heating effect. As the energy is supplied, the foil is heated causing the polymer coating to melt and bond the foil to the container. This process creates a hermetic seal between the foil and the sealing surface (also known as the land area) of the container.
Choosing the Right Lining Material
There are many choices when it comes to induction heat seal liners. Selecting the best induction heat seal liner for your product depends on several factors:
- What material is the container? Some induction heat seal liners are "universal", meaning they can work on both plastic and glass. Other heat seal liners, however, are material-specific.
- Do you need the liner to peel away cleanly, without leaving any residue on the container's sealing surface (Clean Peel), or should the liner need to be punctured as clear evidence that it was not tampered with (Welded Seal)?
- Do you need a lined closure after the tamper evident seal has been removed? If so, is pulp satisfactory or do you need a better quality material to keep your package air tight?
- If using a heat seal liner in conjunction with a child resistant closure, is ease of removal of the closure important? Friction fit liners need to be held in place by the closure threads and will extend beyond the land area of the jar. This overhang will create interference when pushing down while turning to remove the closure.
Once you have answered these questions, it will be easier to determine which type of induction heat seal liner best suits your needs.
Induction liners are available in one-piece or two-piece constructions:
Two-Piece Liners - Traditional Material
(Glued into the Closure)
The two-piece liner is the traditional material you may be familiar with. It is commonly used on plastic motor oil bottles and Tylenol bottles. The liner is glued into the closure. A two-piece liner has a wax layer between the foil and pulp board backing. The induction heating process bonds the foil to the container while also melting the wax, releasing it from the pulp backing. The wax is absorbed into the pulp board backing. The pulp board layer remains inside the cap after the foil liner has been removed. The benefit of the glued-in liner is that the foil will not overhang the sealing surface of the container, which makes the closure easier to open. Glued in liners also reduce the potential for friction fit liners to fall out in handling.One-Piece Liners
One-piece liners are friction fit inside the closure - no glue is involved. These types of liners can consist of a foam-backed or paper-backed foil laminate. The backing provides structure to the thin foil layer.
Lift and Peel liners are a great example of a friction fit liner. A closure with these types of liners can be supplied with a single liner with no additional backing, or they can be double lined with your choice of backing to maintain an airtight seal after the foil is removed.
An "Ear Tab" is another approach to a friction fit liner.
Like the Lift and Peel Liners, this liner is a multi layer construction of a polymer coating applied to a thin layer of foil which is bonded to a foam backing.
Friction fit liners are often supplied by closure manufacturers who do not have the ability to glue liners into the closures. Friction fit liners are an inexpensive choice when a lined closure after opening is not required. Friction fit liners are also the best choice when you want to be able to choose the specific type of liner that will remain in the closure after opening. For example, if a pulpboard liner is not satisfactory, a wide range of other liners can be inserted into the closure prior to friction fitting the heat seal liner (see options below under "Standard Liners").
Options at a Glance
|BACKING: 2 part liner w/ wax between layers||or||NO BACKING - 1 piece liner|
|CLEAN PEEL||or||WELDED SEAL|
|TAB or LIFT N PEEL||or||NO TAB|
|MATERIAL USED ON: (PET/ HDPE)||or||UNIVERSAL|
|PRINTED "Sealed For Your Protection"||or||PLAIN|
|SAFEGUARD 75 - HDPE Welded Seal||2 part liner|
|SAFEGUARD 90 - PET Welded Seal||2 piece liner|
|FS 5-9 - Universal - Clean Peel - Foam/Foil||1 piece liner|
|LIFT N PEEL - for PET/ or for Glass||1 piece liner|
|LIFT N PEEL - Universal with Secondary PP Foam Liner||Double lined|
|HS 035 - Universal - Welded Seal - Polystyrene Foam/ Foil||1 piece liner|
* The materials of construction of foil liners are closely regulated. Food Contact Materials (FCM) Regulation EC 10/2011 (Annex I, Table 1), for example, states that petroleum based or synthetic hydrocarbon derived waxes (which are frequently used in induction heat sealed liner laminates for glass) must not be used for articles in contact with fatty foods.