5 Reasons Why Plastic Bottles Leak

Feb. 15, 2022

89/400Aluminum cap

Even a small leak is a big problem. Leaking plastic bottle caps are an issue whether they occur when your plastic bottles are warehoused, shipped, or placed on the retail shelf for sale. Fortunately, there are measures you can take to mitigate the occurrence of leaking packaging. Let’s break down some potential reasons why cap leakage occurs (and what you can do to prevent it from happening).


Securely attach induction seals to plastic bottles

Another potential source of plastic bottle leakage is an improperly applied induction seal. An induction seal is arguably the best way to seal a plastic bottle for just about any type of product. These plastic liners require an electromagnetic pulse to excite the molecules enough the heat up the induction seal and attach it to the opening of the plastic bottle. However, the improper application will pose problems.

As with the torque issue, too much or too little heat can create leakage issues. Not enough of a sealing time will not completely and correctly attach the induction seal. Too much of a sealing time will burn the seal, which can create small pinholes in the liner that will allow for product leaks.

Just like with caps, induction seal manufacturers can provide recommendations for application. However, you’ll still want to test out potential sealing ranges to make sure your bottles are properly secure. Once you apply your induction seal, lay the bottle down sideways for 24 hours to test it. You can also do 10 sample seals at varying levels to get a good range of potential leakage. Adding weight on top of the sideways bottles can also test the security of the induction seals even further.


Apply the right amount of torque when sealing bottle caps


One of the most common reasons for cap leakage is that the caps are either put on with too much or not enough twisting force. Every type of plastic bottle cap has a certain specified torque range to help ensure proper sealing. Applying a cap with a torque outside of that range is a potential reason for future product leaks.

The reason why too little torque can cause cap leakage is simple – the cap’s soft liner material will likely not be sealed tightly enough to prevent future leaks. Too much torque creates other issues. If you use too much torque, the cap can strip the threads within the cap and cause the closure to become loose. Too much torque can also wrinkle the cap liner within the cap, making product leaks a possibility.

The solution for these issues is two-fold: identify the right torque and test your containers. Your packaging supplier’s engineering team can provide recommended cap torque specifications for your closures. There are also general industry standards available. For example, a 28 mm cap would typically use somewhere around 15 inch pounds of force.

Even if you follow manufacturer recommendations and industry standards, you should always test your plastic bottles and caps for good measure. A bench top tool tester will allow test each product bottle and cap combination. Once sealed, let your containers sit for 24 hours under slight pressure to ensure you have a tight seal and no leakage.


Account for potential stack pressure on top of the plastic bottle

Even if your caps are a perfect fit for your plastic bottles, too much pressure placed on top of the bottle can pose problems in the future. Too much weight coming down on the bottle will create pressure within your container. This excess pressure will put stress on the weakest point of your packaging, which is typically the cap seal. As such, this pressure can cause the cap seal to leak or even completely burst.

As you may expect, you want to ensure that any pressure or weight on top of the bottle won’t break the seal. This issue often occurs when the corrugated box the bottles are shipped and stored and aren’t properly designed to take the weight off your containers, especially when there are pallet loads that are stacked two or three high. Pipeline Packaging can help you test bottles and cartons – especially under humid conditions.


Avoid product and chemical incompatibility

Some plastics and chemicals just don’t work well together. Aggressive chemicals such as acetones and fuel additives can break down your bottles and caps if you don’t use compatible materials.

Fortunately, packaging engineers are a great resource for material compatibility information. These experts can tell you which cap liners are best suited for your fill products, especially if your chemical is more aggressive.

Even after these recommendations, you’ll still want to test your plastic bottle and cap combination to make sure that your fill product won’t pose any packaging problems. Heating the filled bottles in a testing oven will help accelerate any kind of chemical process caused by aggressive chemicals. This process will give you a better idea of how your product may affect the cap liner.


Ensure the cap thread matches your plastic bottle’s neck finish

A mismatched cap thread can definitely lead to leakage issues for plastic bottles. There are different threads types available for plastic bottle caps, but some caps fit better with certain types of neck finishes. For example, a standard 38-400 cap has a single turn of threads, whereas the 410 and 415 models feature additional threads.

This potential for mismatched caps and bottles is why groups like the Closure Manufacturers Association have standardized certain specifications. You can work with Pipeline Packaging to get specification drawings and make sure your cap thread matches what’s on the neck of your bottle. You can also refer to Pipeline Packaging’s Cap and Neck Finish Measurement and Compatibility Guide for more information.


Plastic Bottle Cap Manufacturer

As a plastic bottle cap manufacturer in China, LUhang is committed to providing bottle packaging solutions for dairy products, bottled liquids and other industries. We have a wide variety of plastic bottle caps, such as aluminum caps, bamboo caps, Qianqiu caps, screw caps, and doctors caps,or other caps suitable for various bottles.

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