Information AboutSilicone |
| CATEGORIES ABOUT SILICONE | |
| adhesives | |
| cosmetic chemicals | |
| lubricants | |
| organosilicon compounds | |
| silicones | |
|
Silicones (more accurately called Polymer ized Siloxane s or '''polysiloxanes''') are mixed Inorganic - Organic Polymer s with the chemical formula {Link without Title} n, where R = organic groups such as Methyl , Ethyl , and Phenyl . These materials consist of an inorganic Silicon - Oxygen backbone (...-Si-O-Si-O-Si-O-...) with organic side groups attached to the silicon atoms, which are four-coordinate. In some cases organic side groups can be used to link two or more of these -Si-O- backbones together. By varying the -Si-O- chain lengths, side groups, and Crosslinking , silicones can be synthesized with a wide variety of properties and compositions. They can vary in consistency from liquid to gel to rubber to hard plastic. The most common siloxane is linear Polydimethylsiloxane (PDMS), a Silicone Oil . The second largest group of silicone materials is based on Silicone Resin s, which are formed by branched and cage-like oligosiloxanes. PROPERTIES Some of the most useful properties of silicone include: # Thermal stability (Constancy of properties over a wide operating range of –100 to 250°C) # Though not Lipophilic , the ability to repel water and form watertight seals # Excellent resistance to oxygen, ozone, and sunlight # Flexibility # Good electrical insulation # Anti-adhesive # Low chemical reactivity # Low toxicity # High gas permeability: at room temperature (25°C) the permeability of silicone rubber for gases like oxygen is approximately 400 times that of butyl rubber, making silicone useful for medical applications (though precluding it from applications where gas-tight seals are necessary). SYNTHESIS Silicones are synthesized from Chlorosilane s, Tetraethoxysilane , and related compounds. In the case of PDMS, the starting material is dimethyl Chlorosilane , which reacts with Water as follows: :n + n [H2O → [Si(CH3)2O]n + 2n HCl During polymerization, this reaction evolves potentially hazardous Hydrogen Chloride gas. For medical uses, a process was developed where the chlorine atoms in the silane precursor were replaced with acetate groups, so that the reaction product of the final curing process is nontoxic Acetic Acid (vinegar). As a side effect, the curing process is also much slower in this case. This is the chemistry used in many consumer applications, such as silicone Caulk and Adhesive s. Silane precursors with more acid-forming groups and fewer methyl groups, such as methyltrichlorosilane, can be used to introduce Branches or Cross-link s in the polymer chain. Ideally, each molecule of such a compound becomes a branch point. This can be used to produce hard Silicone Resin s. Similarly, precursors with three methyl groups can be used to limit molecular weight, since each such molecule has only one reactive site and so forms the end of a siloxane chain. Modern silicone resins are made with Tetraethoxysilane , which reacts in a more mild and controllable manner than chlorosilanes. VERSATILE APPLICATIONS |
Image:Sl Silicone PipesjpgSelf-leveling Silicone
| "http://wwwinformationdelightinfo/information/entry/firestop" class="copylinks">Firestop System used around Copper Pipe through-penetrations in a two-hour Fire-resistance Rated Concrete floor assembly |
|
Image:Self Level SiliconejpgSelf-levelling Silicone
| "http://wwwinformationdelightinfo/information/entry/firestop" class="copylinks">Firestop installation in mechanical service penetration in 2 Hour Rated Concrete floor |
|
Image:Silicone Foam Sakno1jpgFaulty Sakno Silicone Foam
| "http://wwwinformationdelightinfo/information/entry/Firestop" class="copylinks">Firestop Installation in Calgary Sewage Treatment Plant in the 1980s, to seal opening above a Fire Door in a cast Concrete Fire separation |
|
Image:FoamfixerjpgSilicone "foamfixer" Pump Used To Apply Silicone
| "http://wwwinformationdelightinfo/information/entry/foam" class="copylinks">Foam Firestop materials |
|
Image:Kieselsaeure380m2progjpg
| "http://wwwinformationdelightinfo/information/entry/Silicon_dioxide" class="copylinks">Silicon Dioxide (silica) used in the manufacture of all silicones This is what remains when one burns silicone burning silicone caulking or foam produces silica (as well as char) as a white powder&ndashsilica fume |
|
|
|