From Silicon to Silicone
The basis of silicone is silicon. Silicon follows oxygen as the second most prevalent element on earth. The surface of the earth consists up to 28% of silicon.
A first process for the production of vulcanized silicone polymers was patented in 1958. The following information explains about the production and chemical composition of silicone. Please also read the details in the instructions for use included with each product.
Silicon is a tetravalent element, therefore it is able to form 4 covalent bonds. It is a member of group IV in the periodic system, directly below carbon.
Silicon has a strong affinity to oxygen. Natural as well as synthetic products based on silicon often contain silicon-oxygen bonds. Due to the valences (4 for silicon, 2 for oxygen) macromolecules can be formed. The silicone matrix containing alternating silicon and oxygen atoms in repeated form is called siloxane.
Molecules which contain several siloxane units are called polysiloxane or silicone. Two carbon atoms, typically in a methyl group (CH3), can be bound to each central silicon atom. Three methyl groups are bound to the silicon atoms at each end of such a chain.
The chains formed are called polydimethylsiloxane; they can be either linear or branched. The length of the chains varies from several units to several thousand units. Silicone can be of a thin consistence, highly viscose or solid depending on the groups bound within the substance and the production process.
Silicone oil consists of linear short chains. Silicone oils – in varying degrees of purity – are to be found as oils in the heating, cooling and hydraulic technology. Such oils are also applied as lubricants or filling material. Additionally, silicone oil is used in the food industry, e.g. for the manufacturing of sugar and processing of vegetables, to reduce the amount of foam produced. This positive effect is also made use of in the treatment of babies with colics. Silicone oil in its purest form is used in the pharmaceutical industry and in the production of medical devices.
Silicone gel is formed if the chains are bound to one another in a three-dimensional matrix. The cross-linking is catalyzed by adding platinum. The material can either be vulcanized at a high temperature (H.T.V.: high temperature vulcanization) or at room temperature (R.T.V.: room temperature vulcanization).
The space within the matrix is filled with silicone oil. Among other things, silicone gel can be used as a filling material for implants. Silicone-gel filled implants closely imitate the feel movement of human soft tissue.
Silicone elastomers are very strongly bonded chains, without much space between the molecules. In order to increase the mechanical stability, silica is added in its amorphous form. With the addition of a very fine silica a transparent silicone elastomer can be produced. Silicone elastomers are used in the production of foods, for example for coating. Silicone tubes are also made from silicone elastomer. All mammary implants, irrelevant of which material they are filled with, have a silicone-elastomer shell.
Further characteristics of silicone:
Silicone is extraordinarily temperature-stable: from approximately -70°C to +250°C. Other positive material features are the high resistance to shearing forces, minimal temporal degradation, and resistance to oxidation and hydrolysis. Silicone, as used for implants, is chemically inert and bio-compatible.
Silicone has been used for medical products for over 40 years. Long clinical experience and a multitude of tests carried out on the implants and coatings, etc. prove the safety of silicone for the use in medical science.