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Basic Silicone Chemistry (I). Silicone Family Tree Si Volatile Methyl Siloxanes Silicone Polyethers Silanes Fluids & Emulsions Silicone Resins Dimethyl.

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Presentation on theme: "Basic Silicone Chemistry (I). Silicone Family Tree Si Volatile Methyl Siloxanes Silicone Polyethers Silanes Fluids & Emulsions Silicone Resins Dimethyl."— Presentation transcript:

1 Basic Silicone Chemistry (I)

2 Silicone Family Tree Si Volatile Methyl Siloxanes Silicone Polyethers Silanes Fluids & Emulsions Silicone Resins Dimethyl Compounds Organo-Silicones Amino Silicones Elastomers

3 Flexibility of Siloxane Chemistry Non-volatile Antifoam Slippery Water Insoluble Excellent Depth of Gloss Incompatible in Organics Durable Volatile Profoam Sticky Water Soluble Shiny Compatible Transient

4 l Aerospace l Automotive l Chemicals/ Petrochemicals l Construction l Consumer Products l Electrical/Electronics l Food Processing l Industrial Maintenance Production SILICONES SILICONES APPLICATIONS Dow Corning’s products and specialty materials are used by customers in virtually every major industry. l Medical Products l Paints & Coatings l Personal, Household & Automotive Care l Pharmaceuticals l Plastics l Pressure-Sensitive Adhesives l Textiles & Leather

5 SILICA O O Si O O SILICON Si SILANES Si X X X X SILOXANES O R R Si O Silicone Nomenclature

6 Silicone Nomenclature Shorthand Precursor Silanol Siloxane Structure Short hand Me Me Cl-Si-Cl HO-Si-OH Linear Structures D unit Me Me Me-Si-Cl Me-Si-OH End-cap group M unit Me Me Cl-Si-Cl HO-Si-OH Branched Structures T unit Cl OH Cl-Si-Cl HO-Si-OH Silica Core Q unit Cl OH Me Me Me Me Me Me Me Me Me-Si-O-Si-O-Si-O-Si-O-Si-Me = Me-Si-(O-Si) 3 -O-Si-Me = Me Me Me Me Me Me Me Me MD 3 M

7 (1)Fluids (hydraulic, release agents, cosmetics, heat transfer media, polishes, lubricants, damping, dry cleaning) Polymer chains of difunctional units (D) terminated with monofunctional (M) units OR cyclics (Dx) (2)Gums (high temperature heat transfer fluids, lubricants, greases, cosmetic and health care additives) Same structure as PDMS fluids, but much higher molecular weight (viscosities >1,000,000 cSt). (3)Resins (varnishes, protective coatings, release coatings, molding compounds, electronic insulation) Rigid solids based on trifunctional (T) and tetrafunctional (Q) units. Surface modification with (M) units (4)Elastomers (Heat cured and RTVs: tubing and hoses, medical implants, sealants, adhesives, surgical aids, electrical insulation, fuel resistant rubber parts, rollers, etc) Soft solids based on crosslinked SiH Fluids Silicone Classifications by Physical Form

8 Raw Materials Initial material is quartz –SiO 4/2 –26% of the Earth’s crust Reduce to Si metal with carbon at 2500F Dow Corning purchases silicon metal & methanol Methanol is converted to MeCl with recycled HCl

9 Process Chemistry of Methyl Train MeCl Si Copper Catalysts Me 2 SiCl 2 MeHSiCl 2 Me 3 SiCl Chlorosilane Mix H2OH2O Waste & Recovery Me2 Hydro SiH fluid EBB

10 Volatile Polydimethylsiloxane Fluids INCI NAME: Cyclomethicone CH 3 Si - O CH 3 n = 3 Trimer n = 4 Tetramer n = 5 Pentamer n = 6 Hexamer n PENTAMER (D 5 ) Si CH 3 OO OO O

11 Volatile Polydimethylsiloxane (PDMS) Fluids When m = 0, R= CH 3 called Hexamethyldisiloxane or 200 Fluid,0.65 cS (.65,1, 1.5 and 2.0 cS are volatile) CH 3 CH 3 CH 3 R - Si - O - Si - O - Si - R CH 3 CH 3 m CH 3 R = CH 3 INCI: Dimethicone R = OH INCI: Dimethiconol

12 Properties of Siloxanes Despite the Fact that Silicon and Carbon are both Group IV elements their chemistry is very different Unique flexibility of Si-O bond Si-O-Si C-C-C C-O-C units bond length angstroms bond angle degree bond energy Kcal/mol bond barrier Kcal/mol

13 Barrier to Rotation ( kcal/mole ) –Polyethylene 3.3 –Polytetrafluoroethylene 4.7 –Polydimethylsiloxane < 0.2 Key Point: Siloxane (Si-O-Si) polymers are stronger than carbon polymers, yet the polymer chains are more open and flexible Siloxane Polymers vs Carbon Polymers

14 Siloxane Physical Properties Very low glass transition temperature (Tg = -120 °C) – high molecular weights but not a solid Ability to spread out on a wide variety of substrates – silky, smooth, non-tacky, aesthetic enhancing – flowability and film forming Lowest surface shear viscosity and low surface tension – lubricating, antifoaming, waterproofing, release properties High gas permeability Excellent dielectric properties Very good thermo-oxidative stability – good chemical inertness and temperature resistance

15 Anionic Ring Opening Equilibrations D4D4 Ring : Chain Equilibrium 10-15% : 85 – 90% PDI = 2.0

16 Anionic Ring Opening Equilibrations End Blockers

17 Anionic Ring Opening Equilibrations End Blockers Viscosity time Maximum in viscosity involves incorporation of end blocker (which is less reactive than cyclic)

18 Living Anionic Ring Opening Polymerization D3D3 sec-Butyl – Li + Living anionic polymerization

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