How A Closure Liner Functions
The only part of a properly functioning closure and liner that comes in
contact with the contents of the package is the face or facing of the
liner. The threads or other parts of the closure perform no sealing
function other than the mechanical one of maintaining intimate contact
between the face of the liner and the glass sealing lip.
A properly functioning liner must fulfill three general requirements:
|Evaluating Closure Liners|
Customers are responsible for evaluating or testing to determine the
suitability of closure design and closure liner material for their
specific product and package requirements. Kenplas has no control over
product formulations, package design, package handling, and storage and
cannot therefore assume any responsibility for customer's choice of
closure or closure liner materials. The entire package including the
closure should be tested and evaluated by the customer to confirm that the
package is satisfactory for its intended use.
Particular care should be exercised in the selection of liners for child-Resistant closure systems. Certain products can alter the effectiveness of child-Resistant closure if exposed to the child-Resistant mechanism or closure components. Therefore, in selecting a child-Resistant closure liner, appropriate testing should be conducted to demonstrate that the package remains child-Resistant and adult-effective throughout its expected shelf life and use.
|Where possible, standard liners are suggested as first choice with nonstandard liner materials as alternate suggestions, providing that standard liners are compatible with the product and are competitive in price. The use of standard liners is advantageous to customers because these materials are generally in stock.|
Tacseal© is the Owens-Brockway designation for an inner-seal liner, which is positioned in the closure and applied over the orifice of the container when the closure is applied. A Tacseal© liner remains in place on the container when the closure is removed and forms a seal until lifted or broken. There are three primary methods of applying the Tacseal© liner, namely, by wet adhesives, heat activation, or pressure activation. The Tacseal© is an extra seal that can add protection for such factors as water vapor and volatile components and protection against contamination and leakage. Tacseal© liners are normally available in sizes through 89 mm C.T. closures.
Again, the customer has the responsibility to evaluate the inner-seal system to be used with the product, the container to be sealed, and the equipment used to close and/ or activate the materials selected.
Three wax treatments are available: Lubricant Finish (LF),
Light Wax (LW), and Full Wax (FW). Each of these coatings is applied at
different coating weights and uses different wax formulations.
LUBRICANT FINISH (LF):
Lubricant finish treatment is used to reduce excessive removal torque buildup typical of vinyl and polyethylene-coated papers. Vinyl and polyethylene-coated papers have a tendency to cold flow, and as such, may result in removal torque buildup. This characteristic is accentuated with time and temperature.
The "LF" coating of wax does not completely eliminate the buildup but does materially reduce its effects to a practical workable range. The "LF" coating is also used with Saran film. Saran film has a tendency to grab the glass-sealing surface during capping, thus causing erratic capping performance, which results in false application values. Closures that appear to be on tight are reduced to approximately zero removal, which has a slight impact on handling. To overcome this tendency and to ensure good application and removal torque performance, the "LF" coating of wax should be used on all Saran liners when product compatibility will allow.
In view of the above characteristics of vinyl and polyethylene-coated papers and Saran film, it is strongly suggested that the "LF" coating of wax be used on these liners at all times, particularly with molded plastic caps with glued-in liners, when product compatibility will allow.
LIGHT WAX (LW)
Light wax treatment is generally used to improve the moisture vapor barrier characteristic of a given liner facing. The type of wax used for this treatment also acts as a lubricant in the same manners that "LF" coating of wax does for vinyl and polyethylene-coated papers and Saran films.
FULL WAX (FW)
Full wax treatment is generally used on wide-mouth closures as a caulking agent. Many liner facings provide a less than satisfactory seal for wide-mouth containers. The larger the finish, the greater the tolerance in both container and finish. The inherent waves and dips of large finishes also contribute to this condition. For this reason, full wax treatment is generally suggested for closures 58 mm and larger.
The full wax treatment will also provide an additional moisture barrier and act as a lubricant similar to the "LW" and "LF" coating treatments.
Abbreviations for duplex liners describe the liner starting
with the backing material and working toward the facing. Everything to the
left of the "slant" is related to the backing material, and everything to
the right of the "slant" is concerned with the facing and its treatment,
|Liner Facings List|
|Unit Liners (No Separate Backing)|
14B White Rubber
White vulcanized styrene-butadiene rubber
Teflon/silicone rubber/polypropylene film
Co-extruded material. Foamed low-density polyethylene core between two solid layers of low density polyethylene
Teflon film laminated on one side to a one-piece 3-ply co-extruded material. Foamed low density polyethylene between two solid layers of low density polyethylene
A closure which has been engineered to function in specific applications without the use of an additional liner
Aluminum foil laminated to paper and bonded to pulpboard
Polyethylene film laminated to paper and bonded to pulpboard
Vinyl coating applied to high density polyethylene coated paper laminated to pulpboard
Tin foil laminated to paper and bonded to pulpboard
Vinyl chloride resin applied as a liquid and baked to a final form
Cone-shaped low density polyethylene liner
Solid virgin Teflon TFE .015"
A closure without a liner
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