Silicone cure systems

== Description ==
Any of a large group of semi-inorganic polymers based on siloxanes. Silicones were first discovered by F.S. Kipping in England in 1904, but were not commercially produced as polymers until 1943 by Dow Corning and 1946 by General Electric. They were called silicones because their empirical formula (R2SiO) is similar to that for ketones (R2CO) (Lewis, 1993). Once cured silicone resins can be liquids, gels, and elastomers as well as solid thermoplastic or thermosetting resins. The curing process, however, can be done by several methods, each resulting in different cure times, volatiles emission and product characteristics.
Chemically, a silicone elastomer can be cured into a solid via an 'addition' reaction or a 'condensation' reaction. An addition reaction may use catalysts (platinum or tin) but the condensation process also requires oxygen and moisture. The addition of UV light or heat will decrease the cure time. Silicone polymers cured in open air at room temperature can be called RTV (Room Temperature Vulcanization).
Types of Silicone cures include:
Classification	Mechanism	By-Product 	Effect 	Comments 	Examples
Acetoxy cure 	Acetoxy 	Acetic acid	Corrosive 	May contain tin catalyst that can be harmful to electronics	
Neutral cure 	Oxime 	Ketoxime 	Mildly corrosive 	May contain tin catalyst that can be harmful to electronics	Dowsil 580, Dowsil 737
Neutral cure 	Alkoxy 	Methanol 	Non corrosive 	Usually one component 	Dpwsil 739 RTV, Dowsil 791, Dowsil 993, Dowsil 795, Dowsil 3145, Dowsil 7091, Silastic 1080
Neutral cure 	Acetone 	Acetone 	Non corrosive 	 	
Neutral Cure 	Amine 	Ammonia 	Reactive with organic materials	Usually used in combinations with alkoxy systems 	
Advantages and Disadvantages of the types of cure systems include:
1-Part Condensation Cure	2-Part Condensation Cure 	1-Part Addition Cure 	2-Part Addition Cure
Easy to apply 	Tolerant catalyst ratios 	Easy to apply 	Excellent deep section cure
No mix-no mix error 	Low risk of cure failure 	No mix-no mix error 	Pot life extension
Easy dispensing 	Deep section cure 	No cure reversal 	No cure reversal
Max 10mm thickness 	Cure acceleration possible 	Adhesion hard to achieve	Cure acceleration with heat
Fixed cure speed 	Small increase in shrinkage	Prone to cure failure 	Optically clear available
Narrow viscosity range 	Cure reversal possible 	Shorter shelf life 	Low shrinkage
Cure reversal possible 	 	 	Prone to cure failure
 	 	 	Requires accurate mix
 	 	 	Good adhesion difficult
== Synonyms and Related Terms ==
polysiloxane; silicona (Esp.); silicone (Fr.); silicone (It.); silicone (Port.); organosiloxane; silicones 
Examples: Silastic [Dow];
== Resources and Citations ==
* Silicone Technologies: Cure Systems
* Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
* Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
* The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
* M.Kaufman, The First Century of Plastics, The Plastics and Rubber Institute, London, 1963
* History of Plastics: www.nswpmith.com.au/historyofplastics.html - discovered by F.S. Kipping in 1904
* Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
Category:Materials databaseCategory:MWGCategory:CaulksCategory:Comparisons