What Are Vial Stoppers Made Of

1. Natural rubber:
Natural rubber is one of the earliest materials used for vial stoppers. Harvested from the latex of the rubber tree, it has good sealing properties and flexibility. However, natural rubber also has limitations, such as the potential for extractables and leachables, which can contaminate the contents of the vial. In addition, some people may be allergic to the proteins in natural rubber, leading to concerns about allergic reactions.
2. Synthetic rubber:
To address the limitations of natural rubber, synthetic rubbers such as butyl rubber and bromobutyl rubber are becoming increasingly popular. Butyl rubber, in particular, is widely used due to its excellent gas barrier properties, low permeability, and resistance to chemical degradation. These qualities make it ideal for maintaining drug stability by preventing the ingress of oxygen and other gases. Bromobutyl rubber has even greater resistance to chemical permeation.

 

 

3. Chlorobutyl rubber:
Chlorobutyl rubber is another synthetic rubber variant used for vial stoppers. It is made by chlorinating butyl rubber to improve gas barrier properties and reduce the risk of extractables. Chlorobutyl rubber is known for its compatibility with a variety of drug formulations and its ability to maintain a tight seal.
4. Fluoroelastomers:

Fluoroelastomers such as Viton are known for their excellent chemical and temperature resistance. These elastomers are highly inert, making them suitable for applications where the stopper must withstand aggressive drug formulations or elevated processing conditions. Fluoroelastomers are also known for their low extractables and leachables.

5. Silicone:

Silicone is popular in the pharmaceutical industry due to its biocompatibility, elasticity, and low extractables. It provides a good seal and is often used for parenteral drug products. Silicone stoppers are known for their elasticity and ability to reseal after needle penetration. However, there are concerns about possible interactions between silicone and certain drug formulations, so thorough compatibility studies are needed.

6. TPE (Thermoplastic Elastomer):

TPE is a new class of materials that combines the flexibility of rubber with the processing properties of plastic. They are thermoplastic in nature and are easy to mold and process. TPE stoppers offer a good compromise between the sealing properties of rubber and the chemical resistance of plastic. They are also known for reducing the generation of particulate matter during the manufacturing process.
7. Polymer Blends:

Some stoppers are made by blending different polymers to achieve specific properties. For example, a blend of bromobutyl rubber and a fluoropolymer can provide a stopper with improved gas barrier properties and chemical resistance.
8. Coated Plugs:

In some cases, a stopper can be coated with a layer of a different material to enhance specific properties. For example, a stopper coated with silicone can combine the benefits of silicone with those of another material to provide the best solution for a given application.