Rubber for Pharmaceutical Gasket

Nitrile butadiene rubber (NBR), also called as Buna-N, or Nitrile, is made from copolymerization of butadiene and acrylonitrile (ACN). ACN content is from 18% o 50%. Higher ACN content means higher resistance to petroleum oil and fuel, but also means lower flexibility at low temperatures. The operating temperature range is -30°F to +250°F (-35°C to +120°C). The most advanced of NBR is oil resistance and abrasion resistance. NBR has also good resistance to many chemicals although those resistance can not be regards as excellent. Moreover, NBR is cheap, so it is widely used for O-ring and gaskets. Water resistance is also important for a sprayer’s gasket because most spray medicines’ solution is water. NBR’s water resistance is good. However, the disadvantages of NBR as a gasket materials is poor OZONE resistance because the pharmaceutical packaging will be sterilized by ozone often. And the irradiation of NBR is also just fair so that multiple gamma ray sterilization should be avoided.

Butyl rubber (IIR) sometimes just called “butyl”, is a synthetic rubber, a copolymer of isobutylene with isoprene. The most features include excellent shock absorption, vibration damping capabilities and very low gas permeability. The operating temperature is from -55°C to +105°C (-65°F to +225°F). The water resistance of IIR is similar to NBR. IIR has also good resistance for many chemicals. The OZONE resistance of IIR is excellent but irradiation resistance is not good. Moreover, IIR has moderate tensile strength and resilience (rebound rating), which is considered as the main reason for IIR not to be used for the gasket of a sprayer. Moreover, poor oil resistance is another reason because small possibility of contacting lubricant during the production of sprayers. IIR is often used for the stoppers of injection vials and glass bottles and flasks. Normally, IIR is not used to make gasket. However, we ever found a gasket, which is guessed to be made of IIR but we can not confirm.

Below list the relative properties of NBR and IIR for usage as the gasket of a pharmaceutical sprayer.

	NBR	IIR
Tear resistance	good	fair
Tensile resistance	good	fair
Resilience	good	fair
Water resistance	excellent	excellent
Oil resistance	excellent	poor
Ozone resistance	poor	excellent
Irradiation resistance	fair	fair
Operation temperature	-30°F to +250°F (-35°C to +120°C)	-55°C to +105°C (-65°F to +225°F)
Chemical resistance	good for diluted acid, diluted Alkalies, alcohol.	good for diluted acid, diluted Alkalies, alcohol.

Resistance to Ozone and Gammy ray refers to the sections “Gaseous Ozone Resistance of Materials” and “Irradiation Resistance of Materials” separately.

Rubber processing must include curing of rubber. Halo rubber makes rubber’s curing easier.

Vulcanization can be defined as the curing of elastomers, with the terms ‘vulcanization’ and ‘curing’ sometimes used interchangeably in this context. It works by forming cross-links between sections of polymer chain which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material.