Difference between revisions of "Silicone cure systems"

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== Description ==
 
== Description ==
  
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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). Silicones can be liquids, gels, and elastomers as well as solid thermoplastic or thermosetting resins. In general, they have excellent heat and chemical resistance and are water repellent. Silicones are used as adhesives, lubricants, protective coatings, release agents, paints, rubbers, coolants, implants, and insulation.
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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 resin|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.
  
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See also
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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).
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* [[Oxime silicone]] (neutral cure silicone)
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* [[Alkoxysilane]] (neutral cure silicone)
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Types of Silicone cures include:
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* [[Acetoxy silicone]] (acid cure silicone)
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{| class="wikitable"
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* Amine silicone (base cure silicone)
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|-
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[[[SliderGallery rightalign|aaiSILICNE.jpg~FTIR]]]
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! Classification
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! Mechanism
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! By-Product
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! Effect
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! Comments
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! Examples
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|-
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| Acetoxy cure
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| Acetoxy
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| Acetic acid
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| Corrosive
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| May contain tin catalyst that can be harmful to electronics
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|
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|-
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| Neutral cure
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| Oxime
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| Ketoxime
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| Mildly corrosive
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| May contain tin catalyst that can be harmful to electronics
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| Dowsil 580, Dowsil 737
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|-
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| Neutral cure
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| Alkoxy
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| Methanol
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| Non corrosive
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| Usually one component
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| Dpwsil 739 RTV, Dowsil 791, Dowsil 993, [[Dowsil 795 Silicone Sealant|Dowsil 795]], [[Dowsil 3145 Silicone Adhesive|Dowsil 3145]], [[Dowsil 7091 Adhesive Sealant|Dowsil 7091]], Silastic 1080
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|-
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| Neutral cure
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| Acetone
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| Acetone
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| Non corrosive
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|
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|-
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| Neutral Cure
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| Amine
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| Ammonia
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| Reactive with organic materials
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| Usually used in combinations with alkoxy systems
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|
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|}
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Advantages and Disadvantages of the types of cure systems include:
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{| class="wikitable"
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|-
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! 1-Part  Condensation Cure
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! 2-Part Condensation Cure
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! 1-Part Addition Cure
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! 2-Part Addition Cure
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|-
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| Easy to apply
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| Tolerant catalyst ratios
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| Easy to apply
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| Excellent deep section cure
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|-
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| No mix-no mix error
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| Low risk of cure failure
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| No mix-no mix error
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| Pot life extension
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|-
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| Easy dispensing
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| Deep section cure
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| No cure reversal
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| No cure reversal
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|-
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| Max 10mm thickness
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| Cure acceleration possible
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| Adhesion hard to achieve
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| Cure acceleration with heat
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|-
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| Fixed cure speed
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| Small increase in shrinkage
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| Prone to cure failure
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| Optically clear available
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|-
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| Narrow viscosity range
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| Cure reversal possible
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| Shorter shelf life
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| Low shrinkage
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|-
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| Cure reversal possible
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|
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|
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| Prone to cure failure
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|-
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|
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|
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|
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| Requires accurate mix
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|-
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|
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|
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|
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| Good adhesion difficult
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|}
 
== Synonyms and Related Terms ==
 
== Synonyms and Related Terms ==
  
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Examples: Silastic [Dow];
 
Examples: Silastic [Dow];
  
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== Risks ==
 
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* Silicone Solutions: [http://www.siliconesolutions.com/media/pdf/SS-5061SDS.pdf SDS for clear gel]
 
 
== Resources and Citations ==
 
== Resources and Citations ==
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* Silicone Technologies: [http://www.siliconetechnologies.com/silicone-adhesive-sealant-gel-conformal-coating-cure-technical-info.html Cure Systems]
 
* Richard S. Lewis, ''Hawley's Condensed Chemical Dictionary'', Van Nostrand Reinhold, New York, 10th ed., 1993
 
* Richard S. Lewis, ''Hawley's Condensed Chemical Dictionary'', Van Nostrand Reinhold, New York, 10th ed., 1993
  
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[[Category:Materials database]]
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[[Category:Materials database]][[Category:MWG]][[Category:Caulks]][[Category:Comparisons]]

Latest revision as of 09:24, 8 May 2023

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

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