Tuesday, September 26, 2023

Factors to Consider When Choosing Caps for Bottles

Everyone knows that the cap on a bottle must fit perfectly to avoid leakage and evaporation. Caps also need to be sturdy enough to keep out contaminants.

Commercially available plastic bottle caps recyclates and specially formulated model caps were analyzed in terms of composition. It turns out that legacy slip agent additives are present in recyclates in amounts comparable to their use level in virgin resins and caps.


There are various material options for the caps for bottles and closures. The type of cap liner used for a particular product depends on the intended use of the product, such as moisture barriers, chemical resistance, consumer safety, or preventing leakage.

Plastic closures are available in thermoset (phenol formaldehyde resin) and thermoplastic (polypropylene or polyethylene). Thermoset plastics have the highest tolerance for temperature changes and provide the most fantastic range of chemical compatibility. They can also be autoclavable, while thermoplastics are not.

Metal caps can be molded in various shapes and have multiple features. For example, some have an oxygen scavenging cum barrier that helps prevent beer from oxidizing and staling the glass bottles, while others are designed to be child-resistant. The most crucial factor is that the cap size matches the neck finish of the bottle. For example, a bottle with a 28-410 neck finish requires a cap with a similar size and style designation.


If you’re bottling beer, kombucha, or any other carbonated drink, you need caps that create an airtight seal to keep your beverage fresh. The lids should also be easy to open without special tools.

Different caps fit a wide variety of bottle sizes. For example, some have a thread that matches the bottle’s neck size for a secure fit. Others have a smooth exterior that won’t leave marks on the bottle and are better suited for water or medication bottles.

Some caps have a liner that’s pressure sensitive and needs no secondary capping equipment to seal the lid on the bottle. This type of cap has a polystyrene foam core coated with PS22 or similar pressure-sensitive liners. The hats look white and usually have the word “Sealed for your protection” or similar text printed. They may also have a wadding size indicated by a number (e.g., 24mm or 28mm). The wadding is a mixture of cellulose and polyethylene that helps the liner adhere to the cap.


Silver crown caps are hassle-free and easy to use. They can be paired over pry-off glass bottles using a capper and crimped to keep the liquid inside safe and sound. These caps also have an oxygen barrier, which helps prevent the staling effect caused by oxidation in beer.

These caps are typically made by injection molding and have exact dimensional tolerances. This allows them to fit tightly over the neck of the bottle and support embossing on top. They can also withstand the demands of food safety regulations and compliances.

Twist caps are also relatively inexpensive and come in many styles and colors. They are usually softer than the metal used for crown caps, which makes them easier to form around the neck threads during capping. They may also feature a cold-activated wad, which turns green when the bottle is cold and lets you know it’s time to drink. These wads are also great for indicating that the contents of a bottle have not been tampered with.


When selecting bottle caps, it is essential to consider safety and convenience. Hats with a twist-to-open, flip-top closure offer ease of use and can help prevent accidental dispensing or ingestion of your product. They also provide a tight seal that helps protect the contents from contamination and moisture. They are available in various colors to differentiate different products or add flair. Some caps also feature child-resistant closures to limit accidental ingestion of harmful substances.

Most bottle caps are made of a different type of plastic than their bottles, making them difficult to separate during recycling. This can lead to contamination at recycling centers and slow the processing of recycled materials. Thankfully, technological advancements mean that bottle caps and lids can be shredded during the cleaning process so that they can be separated by type before being washed and used to make new bottles and containers. This is especially beneficial for the environment as it can help reduce the trash on beaches, which poses a danger to marine life.