---

Silicone rubber, a synthetic polymer, contains a backbone consisting of alternating silicon and oxygen. It is derived from quartz. The compounds range in viscosity from thin oils to gels, to solid resin.

Silicones surpass other elastomers in many performance categories because of their rigid silicon-oxygen chemical structure. Unlike organic polymers that are made up of a weaker carbon-carbon bond, silicones are chemically similar to quartz. The process of polymerization transforms this structure, allowing the silicon-oxygen molecules to become an elastic rubber.

Silicone rubbers are stable throughout a temperature range of -50°F (-46°C) to 450°F (232°C). They are sterilizable by ETO, radiation, and repeated steam autoclaving.

[ Mechanical Properties | Electrical Properties | Biocompatibilities |
| Chemical Resistance | Advantages | Comparative Analysis ]


Mechanical Properties
There are several ASTM standards for measuring mechanical properties of silicone. We base our incoming material qualification on durometer, tear, elongation, and tensile standards.


Electrical Properties
Silicones exceed all comparable materials in their insulating properties as well as flexibility in electrical applications. Silicones are non-conductive and maintain dielectric strength in temperature extremes far higher than those in which conventional insulating materials can perform.


Biocompatiblities
Silicones can be formulated to comply with Biocompatiblity Guidelines for medical products. They are odorless, tasteless, and do not support bacteria growth. Silicones do not stain or corrode other materials. Working with you, TechneMed's engineers will evaluate your device's physical requirements and offer the several silicones. Silicone rubbers, available for molding, range from 5 to 80 Shore A durometer.


Chemical Resistance
Silicones resist water and many chemicals, including dilute acids, oxidizing chemicals, ammonia and isopropyl alcohol. Silicone rubber will swell when exposed to non-polar solvents including benzene, and toluene, but will return to its original shape when these solvents evaporate. Concentrated acids, alkalines, and certain solvents should not be used with silicones.


Advantages
Silicone offers a wide range of advantages to the medical device engineer. Compatible with human tissue and body fluids, silicone material can be formulated and tested for full biocompatibility. Silicones are odorless, tasteless, do not support bacteria growth and are widely regarded in the industry as the superior implant material. They offer excellent thermostability and can be steam, ethylene oxide, or radiation sterilized.

Silicones are naturally translucent, but can be colored with pigments. If radiopacity is desired, it can be achieved through the addition of barium sulphate or other media.

Products fabricated with silicones are easy to clean, and because they retain softness indefinitely, they have excellent shelf lives.


Silicone Rubber Comparative Analysis

When Compared To...	Silicone Material Delivers...
Latex	Lot-to-lot consistency due to controlled synthetic process, vs. organic lot-to-lot variations Superior biocompatibility Higher clarity Better electrical insulation properties
PVC's	Inertness and absence of leachable additives Superior biocompatibility Stability over a broader temperature range Superior sterilization properties
Polyurethanes and Vinyls	Plasticizer- and toxin-free Superior biocompatibility Broader temperature stability Lower compression set Better clarity Greater softness
TPE's	Superior biocompatibility Superior chemical resistance Lower durometer Lower compression set

For a complete understanding of the fabrication of silicone obtain our white paper "Silicone Rubber Material Features and Fabrication Benefits"  Contact us: assistance@TechneMed.com