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Basic Silicone Chemistry (I)

Basic Silicone Chemistry (I). Silicone Family Tree. Elastomers. Silicone Resins. Fluids & Emulsions. Dimethyl Compounds. Silanes. Organo-Silicones. Silicone Polyethers. Volatile Methyl Siloxanes. Amino Silicones. Si. Flexibility of Siloxane Chemistry. Non-volatile Antifoam

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Basic Silicone Chemistry (I)

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  1. Basic Silicone Chemistry (I)

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

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

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

  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 Me Me-Si-Cl Me-Si-OH End-cap group M unit Me Me Me Me Cl-Si-Cl HO-Si-OH Branched Structures T unit Cl OH 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 MD3M

  7. Silicone Classifications by Physical Form (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 ORcyclics (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

  8. Raw Materials • Initial material is quartz • SiO4/2 • 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 Si Me2SiCl2 MeHSiCl2 Me3SiCl H2O Me2 Hydro SiH fluid EBB Chlorosilane Mix Waste & Recovery MeCl Copper Catalysts

  10. CH3 CH3 Si O O CH3 CH3 Si Si CH3 CH3 O O Si Si CH3 O CH3 CH3 CH3 PENTAMER (D5) Volatile Polydimethylsiloxane FluidsINCI NAME: Cyclomethicone CH3 Si - O CH3 n = 3 Trimer n = 4 Tetramer n = 5 Pentamer n = 6 Hexamer n

  11. Volatile Polydimethylsiloxane (PDMS) Fluids CH3 CH3 CH3 R - Si - O - Si - O - Si - R CH3 CH3 m CH3 R = CH3 INCI: Dimethicone R = OH INCI: Dimethiconol When m = 0, R= CH3 called Hexamethyldisiloxane or 200 Fluid,0.65 cS (.65,1, 1.5 and 2.0 cS are volatile)

  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 1.63 1.54 1.42 angstroms bond angle 130 112 111 degree bond energy 106 83 86 Kcal/mol bond barrier 0.2 3.6 2.7 Kcal/mol

  13. Siloxane Polymers vs Carbon Polymers • Barrier to Rotation ( kcal/mole ) • Polyethylene3.3 • 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

  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 D4 Ring : Chain Equilibrium 10-15% : 85 – 90% PDI = 2.0

  16. Anionic Ring Opening Equilibrations End Blockers

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

  18. Living Anionic Ring Opening Polymerization sec-Butyl – Li + D3 Living anionic polymerization

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