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February 2, 2023

Preventing Cap Issues And Ways To Tackle Them

Even a tiny leak can be a problem, and leaking caps can be problematic when plastic bottles are shipped, stored, or placed on a retail shelf. There are steps you can take to prevent such leakages. Let's look at some possible causes of cap leakage and what you can do to stop it from happening.

How to Keep Plastic Bottles Leak-Proof

Use the correct amount of torque to seal bottle caps.

An excessive or insufficient twisting force can cause cap leakage. To ensure proper sealing, every type of plastic bottle cap comes with a torque range. Any cap that exceeds this torque range could lead to product leakage and too little torque can lead to cap leakage. This is because the cap's soft lining material won't be sealed tight enough to prevent future leakages. Too much torque can cause damage to the cap's threads and loosen the closure. Over-torque can cause product leakage by wrinkling the cap liner.

These issues can be solved by testing your containers and identifying the correct torque. The engineering team at your packaging supplier can recommend the correct torque specifications for your closures. There are also industry standards like a 28mm cap would typically require around 15 inches of force.

You should always test plastic caps and bottles, regardless of whether you follow industry standards and manufacturer recommendations. You can test every product bottle and each cap combination with a bench-top tool tester. Let your containers rest for 24 hours, preferably under light pressure which will help you to ensure there is no leakage.

Attach induction seals to plastic bottles

Induction seals not applied correctly can also lead to plastic bottle leakage. Induction seals are the best method to seal plastic bottles for almost any product. To heat the plastic liners, an electromagnetic pulse is required to compel the molecules to heat the material and attach it to the bottle's opening. Though, mistakes in the application can cause problems.

Like the torque issue, too little or too much heat can cause leakage problems. Induction seals will not be adequately attached if there isn't enough time to seal. Expending too much time on the seal can cause it to burn, leading to small holes in the liner, allowing product leakage.

Induction seal manufacturers can offer recommendations on how to apply them, just like caps. To ensure your bottles are secure, you will still need to test different sealing ranges. After applying your induction seal, place the bottle sideways for 24 hours. To get an accurate range of leakage potential, you can do 10 samples at different levels. You can further test induction seal's security by adding weight to the sideways bottles.

Make sure the cap thread matches the neck finish.

A mismatched cap thread can cause leakage problems for plastic bottles. There are many thread types for plastic bottle caps. However, some caps will fit better with specific neck finishes. A standard 38-400 cap features a single turn of threads. The 410 and 415 caps have different threads.

Pipeline Packaging can provide specification drawings. They will also help you ensure that your cap thread matches the neck of your bottle. Pipeline Packaging's Cap & Neck Finish Measurement & Compatibility Guide provides more details.

When you're trying to determine ways to prevent your caps from leaking, your packaging supplier can be one of your greatest asset. Our team at Metro International can help you choose the right closures to fit your containers.

Metro International
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