Gasket is to used to prevent leaking between closure and bottle. Three materials are used to make gakset mainly, including foamed PE, silicone, and rubber.
Rubber gasket. Rubber has good elasticity so the sealing is very good. However, two disadvantages limit the rubber gasket’s application in pharmaceutical sprayers. Firstly, the rubber material of a gasket is nitrile butadiene rubber (NBR) that is not food grade. The Butyl rubber (IIR) for the cap of injection vial is not used to make gaskets. Secondly, low chemical resistance and ageing lead to the decrease of elasticity. Therefore, the pharmaceutical sprayers don’t use rubber gaskets.
Foamed PE gasket. This gasked is made of LDPE that is treated in a foaming procedure. The advantages of a foamed PE gasket is food safe and cheap. Therefore, the foamed PE gasket is the most often used gasket in pharmaceutical sprayers with SCREW on type closures. The sealing ability can meet the requirements for most liquid. However, because of moderate elasticity, some special liquid is easy to leak if the foamed gasket is used. Based on our experience, high concentration alcohol and oil often have leakage, especially the glass bottles are used.
Injection PE gasket. Compared with foamed PE gasket, the injection PE gasket is more rigid and less elastic. Foamed PE gasket is used for SCREW on type closures. However, SNAP on and CRIMP on closures should use Injection PE gasket, because injection PE gasket’s higher rigidness can suit the higher pressure by snap on or crimp on closure. Injection PE gasket is made of the mixture of PE and POE(Polyolefin Elastomer, one type of polyolefin like PP and PE) via injection mold. It doesn’t need foaming treatment. The injection PE gasket is also cheap. The disadvantage is the lower elasticity, so the injection PE gasket can not be used in screw on type closures.
Silicone gasket. Silicone gasket is the best gasket. Silicone gasket has very good food safety and very good elasticity. Normally, when PE foamed gaseket or injection PE gasket can not prevent leaking, silicone gasket will be used and the leakage proof is effective. The only limitation of silicone gasket is the price is very expensive. The price of a silicone gasket is even a few times of the price of a PE gasket.
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