When designing product packaging for medications, supplements, or lifestyle products that consists of bottles and closures, it’s important to select the proper closure liner so the product is protected and the packaging functions properly.
Closure liners are designed specifically for different types of products. Choosing the right liner not only protects your product and the consumer, it can also save you money. At Drug Plastics, we help our customers select the correct, most cost-effective liner for their product.
Primary Liner Functions
The liner exists to perform two primary functions:
- The liner is used to create the initial seal on the bottle and closure. This protects the contents inside the package until it is opened by the consumer. Some liners can Increase the shelf life of the product for extended periods of time by protecting the product from external elements that may negatively affect the product (i.e. moisture, oxygen, and other elements).
- The liner can serve as a reseal device that provides on-going protection after the initial opening of the product.
Certain liners can also provide enhanced child resistance by limiting access to the product and preventing children from misusing it. Some heat induction foil seal liners even serve as a tamper-evident device, alerting the consumer that the package may be compromised.
Liner Materials
Liners are composed of three main classes of materials:
Foam – Various thicknesses of Low Density Polyethylene (LDPE) extrusion or co-extrusion, Polypropylene (PP), Expanded Polyethylene (EPE) or Polystyrene (PS). Standard thickness are .020”, .030”, .035” and .040”, but other thicknesses may be available. Commonly requested liner materials are Uni-foam, F217, and F828.
Pulp – Various thicknesses of cellulose are available. Standard thicknesses are .020”, .030” and .035”, but other thicknesses are available.
Optional facings – Multiple layers of Saran™, Polyethylene Terephthalate (PET), and/or foil can be added to either foam or pulp substrates. Facings are barriers that possess differing chemical resistance and permeability for different liquids and gasses. Barriers also differ in their physical properties which affect ease of opening.
Deciding which Liner Type is Best
Deciding which liner type is best for a product requires careful evaluation. Here are the two main factors to consider:
- The material of the bottle the liner will be sealing to.
- The product that will be packaged inside.
Liner Types
There are seven major categories of liners where the liner materials mentioned above are used alone or in combination. These categories include:
Standard Foam Liners – These liners do not comply with FDA tamper evident requirements. They do not create a hermetic seal, also known as a tight container seal. The standard foam liner is a three-ply co-extruded liner consisting of a foamed LDPE core sandwiched between two layers of solid LDPE.
Standard Pulp Liners – These liners do not comply with FDA tamper evident requirements. They do not create a hermetic seal, also known as a tight container seal. The standard pulp liner is a cardboard-like liner made of cellulose.
Modified Foam Liners – The standard foam liners can be modified by having different types of facings bonded to them. This type of liner consists of LDPE extrusion or co extrusion, PP, EPE, PS foam.
Modified Pulp Liners – The standard pulp liners can be modified by having different types of facings bonded to them. These pulp liners may have a barrier layer or multiple layers laminated to the pulp for specific barrier requirements.
Pressure Sensitive Foam Liners – Pressure sensitive liners are Polystyrene (PS) foam with a torque-activated adhesive. The adhesive bonds to the land area of the bottle. This type of liner does not comply with FDA tamper-evident requirements and is not recommended for liquids. Pressure sensitive liners are for initial sealing only, and have been replaced by induction seal liners in much of the market.
Induction Seal Liners – Induction sealing is the process of bonding thermoplastic materials by using a combination of pressure, heat, and time. This involves controlled heating of an electrical conducting object (usually aluminum foil) by electromagnetic induction. This process bonds the heat seal layer of a multi-layer induction seal liner to the land area of the bottle. Some types of these liners comply with FDA tamper-evident requirements. They also come in various configurations.
One-Piece Induction Liners – Foil is required. These liners contain multiple layers, and each liner contains a backing for strength and liner retention inside the closure. The backing can be made of paper or foam. The layers can be bonded together using adhesive lamination (standard), solvent-based bonding (which is more robust), or extruded resin bonding (the most robust).
- Induction heat softens heat seal surface.
- Initial tight container seal is created on the land area of the bottle.
- Tamper-evident and Clean-peel capable.
- Can contain one or many facings or films for barrier such as PET.
- Barrier properties come from the foil facing.
- Selected facing layers can be printed.
- Does not work as a reseal.
- Best for wide-mouth & dispensing closures.
Two-Piece Induction Liners – Foil is required. These liners contain multiple layers, and each liner contains a backing for strength and liner retention inside the closure. The backing can be made of either pulp or foam for use as a re-seal liner. The foil liner layers can be bonded together using adhesive lamination (standard), solvent-based bonding (which is more robust), or extruded resin bonding (the most robust). The backing is bonded by a wax layer.
- Induction heat softens heat seal surface.
- Induction heat also melts temporary wax so the backing separates to remain inside of the closure.
- Initial tight container seal is created on the land area of the bottle.
- Tamper-evident and Clean-peel capable.
- Can contain one or many facings.
- Barrier properties come from the foil facing and backing.
- Selected facing layers can be printed.
- Backing works as a reseal.
A Trusted Partner
Our team of experts will help you select the best liner for your product – a cost effective packaging solution that will enhance your brand, reduce your risk, and improve your profitability. We have over 60 years of experience helping our customers navigate packaging design decisions and creating the cost effective package that is the best for every product. Let us help you create packaging that will enhance your brand and protect your product for your customers. For more information, speak with someone immediately at 610-367-5000.
Read the second article in this series: “How to Choose the Best Liner for Your Product Packaging”.
For additional and more in-depth information about liner types, we invite you to visit https://www.seligsealing.com/.
