Knowing how to specify the correct Child Resistant cap and liner can save lives and keep you out of court.
Too often brand owners and contract fillers are purchasing CR (child resistant) closures without spending the time to understand the importance of how their product will interact with the closure design and liner material used. While packaging cost is ever more important, the cost associated with defending yourself in an injury or wrongful death lawsuit far outweighs it. By following a few simple steps and having a general understanding of the Federal Regulations, packagers can greatly minimize their exposure to litigation and, more importantly, save young lives.
In the United States today there are primarily two types of CR closures used on most rigid containers. These types are designated as American Society for Testing Materials (ASTM) type 1A and 1B by the Consumer Product Safety Commission (CPSC). Type 1A closures consist of two pieces having an outer shell that spins freely until pushed down and turned counter clockwise to remove from the container. These are commonly know as ‘Push and Turn’ closures. They are attractive to packagers as they will most often fit on standard neck finishes used with non-CR or ‘standard screw caps.’ Type 1B closures are generally single piece and require a squeeze force to be applied to the sidewall as the cap is turned counter clockwise to open. This style cap is very commonly found on mouth wash containers in the United States and is commonly referred to as ‘Squeeze and Turn’. They require a special lug feature on the container to engage with a lock on the closure.
While type 1A push down and turn closures have been used for over forty years and have saved countless lives, they have an inherent problem that is not being detected by the testing required by the CPSC. These tests were established to insure the package design meets the intent of the law, that is: children, in a pre-described amount of time, will not be able to open it. Most successful designs utilize the fact that children in the test age range lack the cognitive skills to apply two dissimilar motions, simultaneously. This test has been refined over the years and is very good at weeding out poor designs. For obvious safety reasons, the test packages never contain actual product. What the test protocol does not look at is the effect of the intended product on the functionality of the closure over time. For a CR package to truly be effective, it must work not only on the store shelf but possibly days, weeks, and even years after purchase and initial opening.
There are just a few materials used for containers, glass, plastic, and metal. Packagers are careful to select the right container that makes sense for the filling equipment, product compatibility, and marketing look they are after. But how often are you thinking about the liner? That little round piece of paperboard or synthetic material, glued or friction fitted into the closure, is critical to the long term function of the package. Liners form a compressive surface to insure a seal between the bottle opening and the inside of the closure. They come in a wide variety of materials. They can even be bonded to the container using conduction or induction foil. What is often overlooked is how the product will interact with the liner or the reseal portion of the liner (in the case of foil bond materials.) A liner can be as simple as a piece of extruded plastic or pulp board, or it can have multiple layers of synthetic materials, each with unique barrier properties. The liner can be designed to carry a heat seal foil either wax or adhesively bonded to its base material. This foil provides barrier properties until the package is initially opened, but once perforated or removed, the clock is running. Now it is up to the reseal liner and proper re-application torque to provide the barrier.
Determining the right liner type for your product requires both input from the closure manufacturer’s technical staff and an educated purchasing agent, not just a recommendation from a distributor or salesperson. In today’s environment of staff reductions, it is becoming harder and harder to get the information you need to make these important decisions. Customer Service staffers, many having never having received training on liner types, often lack the technical knowledge to ask the right questions, let alone give the right answers. Your best source of knowledge is to ask the cap supplier for the liner manufacturer's specification and to call the liner supplier directly. The liner supplier may be hesitant at first since you are not their direct customer, but once they understand your desire to select the proper material they will supply you with a wealth of information. You know what you are filling and they know the barrier properties of the materials they sell.
Unfortunately, there are many materials with almost the same code designations. One missing letter in a code may mean you saved a few cents on the price, but the material is not going to provide the barrier you need. Long term barrier property is of utmost importance. In the case of hydrocarbon products such as Mineral Spirits, Paint Thinners and Lamp & Torch Fuels, if the liner does not provide a barrier the plastic in the cap is exposed. This can be a serious problem for type 1A closures since the undercap swells due to uptake of hydrocarbon vapors and/or liquid. This swelling closes up the design tolerance between the inner and outer cap potentially causing them to lose their ability to freewheel. The cap has essentially become a standard screw cap offering no child resistant protection- that few seconds or minutes when a child is out of an adult's range of view. This problem has been made worse by the fact many products are now in clear PET containers and look very much like juices children are familiar with. Take a look at apple juice and lamp/torch fuel on the shelf next time you shop.
It is not enough to have your package pass CPSC protocol. Stability testing should always be done. Consider the environment the package will be used in over its life. Establish a test criterion for life testing and repeat it periodically. Document your findings. Don’t wait until a crisis to start testing. CR functionality is the responsibility of the brand owner. Don’t assume you can push this back on the cap supplier when you get a notice you are being sued. If you use type 1A - push and turns and your test results show swelling and locking up, perhaps a change in liner type or selecting a more forgiving 1B squeeze and turn type package is the answer. While barrier may still be the issue, squeeze and turn type pack as to tolerance. If you are filler, make sure your employees know that specific product codes are for specific substitute just because the cap will fit and not leak when you turn it over. Educate your Quality, Customer Service, and Purchasing staff about liner types. Ask suppliers to come in and teach your people the importance of liner selection. Hire a consultant if you can’t get the help you need otherwise.
Clayton Robinson has spent over thirty years in the closure industry as a Manufacturing Supervisor, Quality Assurance Engineer, QA Manager, and Product Design Engineer. He holds a Masters degree in Industrial Management from The University of Southern Indiana. His company, Precise Packaging Services, performs packaging consulting, product design, testing, and expert witness testimony.