1. Basic Silicone Chemistry (I)

2. Silicone Family Tree Si Elastomers Fluids & Emulsions Silicone Resins
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.
Aerospace
Automotive
Chemicals/ Petrochemicals
Construction
Consumer Products
Electrical/Electronics
Food Processing
Industrial Maintenance Production
Medical Products
Paints & Coatings
Personal, Household & Automotive Care
Pharmaceuticals
Plastics
Pressure-Sensitive Adhesives
Textiles & Leather

5. Silicone Nomenclature
SILICA
O Si O O X
SILANES X Si X X R
SILOXANES O Si 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-Si-Cl Me-Si-OH End-cap group M unit
Cl-Si-Cl HO-Si-OH Branched Structures T unit
Cl OH
Cl-Si-Cl HO-Si-OH Silica Core Q unit
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 =
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 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

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
Me2SiCl2
MeHSiCl2
Me3SiCl
H2O
Me2 Hydro
SiH fluid
EBB
Chlorosilane
Mix
Waste &
Recovery Si
MeCl
Copper Catalysts

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

11. Volatile Polydimethylsiloxane (PDMS) Fluids
R = CH INCI: Dimethicone
R = OH INCI: Dimethiconol
CH CH CH3
R - Si - O - Si - O - Si - R
CH CH m CH3
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 angstroms bond angle degree bond energy Kcal/mol bond barrier Kcal/mol

13. Siloxane Polymers vs Carbon Polymers
Barrier to Rotation ( kcal/mole )
Polyethylene
Polytetrafluoroethylene
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
The flexibility of the backbone provides one very unique distinguishing point compared to organics: very low glass transition temperature that allows high molecular weights (as high as 500,000) to still be fluid. At the same time, the chemistry kit will allows for water-like volatiles, to rubber-like, tacky or solid resins. Further, since the molecule can easily rotate, the surface tension becomes low from the methyl groups and allows for easy spread for silky, smooth, non-tacky aesthetic non-greasy or oily feel.
Compared with conventional organic polymers, many silicones show superior thermal properties. Some silicone elastomers, for example, remain flexible at - 100C and retain their properties for long periods at 200 C. Most of the common silicone polymers are quite hydrophobic but are permeable to water vapor and to other gases. Their resistance to unltraviolet and other radiation means that they weather well. They are good electrical insulators.
The low surface tensioin of polydimethylsiloxanes (~20 dynes/cm) permit them to spread easily over irregular surfaces. They are often used as additives to promote easier application and to give additional water repellency to the surface.
Some silicones are excellent release agents; even the most aggressive organic adhesives do not adhere to them. Most silicones are not
particularily solvent resistent; however, elastomers made from siloxnes substituted with fluoro groups show good resistance to hydrocarbons ans such.

15. Anionic Ring Opening EquilibrationsD4
Ring : Chain Equilibrium
10-15% : – 90%
PDI = 2.0

16. Anionic Ring Opening Equilibrations
End Blockers

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

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