Storing and Handling PP Unlined Closures Properly

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Storage conditions such as time, temperature, and humidity can have an effect on unlined polypropylene (PP) closures. The exposure and age can also affect the shrinkage, and impact properties of the closure.

Storage Time
The storage time of unlined closures should be minimized. A strict first-in first-out inventory should be maintained. Many end users will re-approve closures after two or three years of storage.

Storage Temperature
Elevated storage temperatures allow unlined polypropylene closures to further shrink. Harsh conditions can actually cause severe distortion. The degree of distortion and shrinkage depends on the closure design and storage conditions.  Higher storage temperatures also accelerate the aging process of the closure. Moderate storage temperatures should be provided to insure consistent closure dimensions and properties.  PP unlined closures can withstand temperatures of 110°F for brief periods.

Storage Humidity
Although humidity itself will not degrade the unlined closure, a humid environment can have a direct impact on the secondary packaging, such as cardboard cartons. Use of stretch wrapping and/or controlling warehouse conditions will help alleviate secondary packaging problems.

Surface Contamination
PP unlined closures should be kept as clean as possible; it is best to store in original sealed cartons.


Have questions about storing and handling unlined closures? Call 610-367-5000 to get answers.

Please note that the above conditions apply to unlined closures. For lined closures, please refer to the Liner Manufactures Storage and Handling Conditions.

The information and recommendations on this page are believed to be correct. However, no guarantee or warranty of any kind, express or implied, is made as to such information contained herein, including any warranty of fitness or merchantability, and Drug Plastics assumes no responsibilities for the results of use of the information described herein.