by Suzie Fenton
When choosing closure and bottle combinations, consideration to how the package is going to be sealed should be addressed. This post refers to Land seals. Land seals are created by the closure applying downward force on to the bottle land thus creating a seal. Usually the closure will have a sealing feature inside of it that comes into contact with the land. A few examples are Crab Claw, V seal, flat seal, and a liner.
(An explanation of the terms “finish” and “land” will be helpful here. The finish is the part of the bottle on which the closure fits; the land is the top of that finish where the underside of the closure’s top “lands” or connects with the bottle.)
The liner has been in use for a long time and people are very familiar with the F217 liner. These closed cell foam liners were used on Continuous thread closures and were very successful, but did add cost to the component (liner cost, and labor cost to insert). When dispensing closures are needed this type of seal typically cannot be used, as it would block the dispensing orifice. Closure manufacturer designers came up with the idea of linerless closures to get around this issue.
Linerless closures would include the Crab claw, V seal or a flat seal. The flat seal typically was the least effective, but did have its place for more viscous products. The V seal was typically used in the Tube industry, as you have to have a very flat land for this seal to be effective. These tube lands were injection molded so they were very flat and free of variation. Trying to use this type of seal on an EBM (Extrusion Blow Molded) bottle would increase the risk of leakage due to potential variation in the land neck finish.
The Crab claw seal is probably the most versatile as it is designed to be flexible and compress slightly, thus can take up some variation in the land of the bottle. They are commonly used on Dispensing closures as well as Continuous threaded closures. An important note here is that the closure manufacturer should provide a recommended neck finish that states what dimension the I.D. of the bottle should be. If this is not duplicated on the bottle, increased incidents of leakage can occur. Many times we see that the crab claw feature falls into the I.D. of the bottle thus rendering itself ineffective in sealing because the I.D. is too large..