Rubber

Natural Rubber (cis 1-4 polyisoprene): Natural rubber is obtained by coagulation of the latex of a tree known as the Heveas Brasiliensis. Although it has good mechanical properties but these are unfortunately coupled with some drawbacks. The disadvantages of natural rubber are poor impermeability to gas and steam, poor ageing performance when exposed to heat and air, release many substances by extraction during storage or sterilization and has tendency to bloom.

Synthetic isoprene (Polyisoprene): This elastomer is obtained by polymerization of a hydrocarbon of formula known as isoprene which is produced from petroleum products. The structure and properties of this elastomer are similar to natural rubber. It is used as an alternative to natural rubber for producing products for people with latex allergies.

Butyl (Isobutylene Isoprene): Butyl rubber is obtained by co-polymerization of isobutylene and isoprene which come from petroleum. It has a very good impermeability to gas and steam, good resistance to oxidization, ozone, acid and base but poor mechanical properties. Butyl stoppers are therefore used for packing very high hygroscopic powders or lyophilized products or highly oxidizable items. Occasionally, it is used for some applications such as syringe plungers and droppers.

Bromobutyl/Chlorobutyl (Bromo/Chloro Isobutylene Isoprene): These elastomers are obtained by continuous halogenization of butyl rubber. There is no significant distinction between bromobutyl and chlorobutyl as the properties of these elastomers are very similar. Halogen has only slight effect on the principal characteristics of butyl rubber. The most important property of bromobutyl and chlorobutyl is also very good gas and steam impermeability. Comparing to butyl, bromobutyl and chlorobutyl have better resistance to hot air and steam, and exceptional chemical inertia. The main applications are stoppers for injection vials and infusion bottles, and plungers for prefillable syringes or dental cartridges.

Ethylene Propylene Diene Monomers (EPDM): This elastomer exhibits satisfactory compatibility with alkaline solutions. EPDM stoppers are intended for use with high pH aqueous solutions, pH 10 or higher.

Nitrile rubber (Nitrile butadiene rubber): This elastomer is a copolymer of acrylonitrile and butadiene. It has good resistance to animal, vegetable and mineral oil. Nitrile rubber stoppers are recommended for use with oil base injectable preparations.

Silicone rubber (Methyl vinyl silicone): Silicone rubber is a rubber-like material composed of silicone-itself a polymer-containing silicon together with carbon, hydrogen and oxygen. Silicone rubber is generally inert, non-reactive, stable and resistant to extreme environments and temperatures from -55°C to +300°C. Due to such, it is intended for applications requiring resistance to high temperature or multiple steam sterilization cycles.

Thermoplastic elastomers (TPE): These materials are a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. TPE's do not require vulcanization and can be precision molded to exceptionally close tolerances. Advantages include cleanliness, low extractables and the capacity for fully automated manufacturing.