Shrink sleeves or bands, as they are sometimes called, are commonly used on many types of packaging from mouth wash to food packaging to OTC drugs. These tamper indicating sleeves drops over the containers cap and uses a heat source to shrink the band onto the cap and neck finish area of the container. This band must now be pealed away to gain access to the cap. With the rapid expansion of Marijuana products in the U.S. many new businesses and brands are coming into the market. Many require Child Resistant packaging. Most also need tamper indication of some type. To be clear: Child Resistant (CR) and Tamper Evident (TE) are two different aspects of packaging and should not be considered synonymous terms or features. This paper focuses on just shrink sleeve TE when it is used in conjunction with Push Down & Turn style child resistant caps.
If you are a brand owner and have selected an ASTM type 1A push down and turn two piece cap along with a shrink band for your product you need to be aware that if the band is not properly applied, the cap may not be child resistant. Most Push & turn CR caps use ratchet teeth between the outer cap and the inner cap that must be held down (pushed) while unscrewing. Two dissimilar motions used simultaneously is the method adults can do while most children, in the age group we are trying to protect, lack that cognitive ability to do BOTH simultaneously.
Shrink sleeves offer a simple why to insure no one has opened the container prior to the purchaser. Proper application over a P&T cap requires that the band must not extent above the top of the closure prior to going through the heat tunnel to shrink it down. If the band is too long when it shrinks it will come over the top of the cap. Since the bottom of the band has shrunk under the transfer bead or other feature below the cap it has now squeezed the cap down, ratchet on ratchet. This leaves no room for the over cap to “walk” up the internal ramps when reverse rotated/removed. One of the key feature’s, push downhas overridden. If application torque is low, the cap only needs to be turned to open. Another key reason to put this type cap on tightly.
The solution is simple: Ensure that the cut length of the sleeve is such that when dropped onto the container and is resting on the neck chime, it is not long enough when shrunk to roll over onto the top of the cap. Should a child try to turn the cap with the TE band still on, the ratchet ramps inside the cap are free to move up.