1. • Silicone functional units R3SiO1/2 : Monofunctional, M
Chapter 4. Silicones 4.1 Structure and properties • Poly (organosiloxanes) only industrially important polymers
• Silicone functional units
R3SiO1/2 : Monofunctional, M
R2SiO2/2 : Difunctional, D
RSiO3/2 : Trifunctional, T
SiO4/2 : Tetrafunctional, Q
where R-methyl or phenyl

2. • Linear poly(organosiloxanes) - a combination of M terminal units and D units • Poly(organosiloxanes) with D units only. Either cyclic or linear with hydroxy or alkoxy end groups • Incorporation of T and Q units => Branched poly(siloxanes)

3. • Silicone Properties • High temperature stability • Resistance against oxidation and weathering • Hydrophobicity • Antifoaming or foam-stabilizing properties depending on structure • Adhesive • Electrically non-conducting • High Gas and vapor permeability • High stability in physical properties with T • Physiologically Harmless

4. 4.3. Silicone Manufacture Synthesis of starting materials - Most important starting materials (chloro) Methyl silane (chloro) phenyl silane Chloromethyl silane - Direct Synthesis process by Rochow and Müller Si + 2CH3Cl Cu (CH3)2SiCl ℃ in fluidized reactor (99% purity powder) 2-6% Cu as a catalyst(mostly CuO) % Zn(ZnO) as an activator

5. • Byproduct CH3SiCl3, (CH3)3SiCl, CH3SiHCl2 4. 3. 1. 2
• Byproduct CH3SiCl3, (CH3)3SiCl, CH3SiHCl (Chloro-)Phenyl- and (Chloro)methylphenylsilane • (Chloro-)phenyl silane Direct synthesis from silicon and chlorobenzene at 500℃ Si + 2C6H5Cl Cu(HCl) (C6H5)2SiCl ℃ Si + 2C6H5Cl + HCl C6H5SiCl3 + C6H CVD

6. HSiCl3 + C6H5Cl 550~650℃ C6H5SiCl3 + HCl • (Dichloro-)methyl phenyl silane CH3HSiCl2 + C6H5Cl 550~650℃ C6H5(CH3)SiCl2 + HCl Other industrially important silanes 1) (Chloro)Vinyl- and (Chloro)methyl Vinyl Silanes CH2=CH2(CH3)nSiCl3-n cross-linking silicone Rubbers

7. 2) (Dichloro) methyl (3.3.3-trifluoropropyl) Silanes CF3CH2CH2(CH3)SiCl2 - manufacture of modified poly(organosiloxanes) 3) Organo-functional siloxanes • Trialkoxy(3-aminopropyl)silanes : H2N(CH2)3Si(OR)3 • Trialkoxy(3-mercaptopropyl)silanes : HS(CH2)3Si(OR)3 • Trialkoxy(3-methacryloxypropyl) silanes - mainly as adhesion promoters for glass fiber-reinforced plastics and the surface treatment of fillers

8. • Manufacture Addition of the appropriate alkene or alkyne to hydrogen-containing silanes w/t. Pt compound • Hydrosilation : 수소화 규소 첨가반응 Si-H + H2C=CH-R Pt -Si-CH2-CH2-R Si-H + HC≡C-R Pt Si-CH=CH-R

9. 4. 3. 2. Linear Poly(organosiloxanes) 4. 3. 2. 1
Linear Poly(organosiloxanes) Synthesis of oligomeric precursors • Most important silicone products Based on (Chloromethyl)silanes with the derivatives of (dichloro) dimethylsilanes i.e. Silicone elastomer & silicone oils • High molecular weight poly(dimethylsiloxanes) <= linear and cyclic dimethylsiloxanes <= Hydrolysis or methanolysis of(dichloro) dimethylsilane

10. ⊙ Hydrolysis of (Dichloro) dimethylsilane • Cyclic CH CH nCl-Si-Cl + nH2O Si-O nHCl CH CH3 n • Linear CH CH3 nCl-Si-Cl + (n+1)H2O HO-Si-O-H + 2nHCl CH CH3 n

11. Continuous reaction In liquid phase w/t
* Continuous reaction In liquid phase w/t. 25% HCl solution or In gas phase at > 100℃ • Liquid phase reaction Linear/cyclic siloxanes formed w/t. 28~35% :1 ~ 1: HCl acid(aq) • Vapor phase reaction CH3Cl by CH3OH technically more complicate due to corrosion problems

12. • Advantage production of gas phase HCl Easier to form CH3Cl ⊙ Methanolysis of (Dichloro) dimethyl silane • Products : CH3Cl and α,β -dihydroxy dimethyl siloxane(yield:>98%) cyclic poly(dimethyl loxane) n(CH3)2SiCl2 + 2nCH3OH [(CH3)2SiO]n + 2nCH3Cl + nH2O

13. ⊙ Purification - only highly pure dichlorodimethyl silane ( > 99
⊙ Purification - only highly pure dichlorodimethyl silane ( > 99.99%) => linear and cyclic dimethylsiloxane oligomers => Manufacture of high molecular weight linear poly(dimethyl siloxanes) Trace of ( trichloro) methyl silane => Troublesome

14. Otherwise, CH CH3 Si-O and HO-Si-O-H CH3 n CH3 n KOH Cyclic dimethyl siloxanes + >160℃ Trifuctional impurities D3: Hexamethyl trisiloxane D4: Octamethyl tetrasiloxanes or Larger

15. D3 : (CH3)2Si O Si(CH3)2 O O Si (CH3)2 D4 : (CH3)2Si O Si(CH3)2 O O (CH3)2Si O Si(CH3)2

16. Then, D3, D4 or larger Distillation and D3, D4 & larger Trifunctional impurities Synthesis of high molecular weight Linear poly(dimethyl siloxanes) Silicone oil and silicone rubber • Manufactured either from 1) Cyclic methylsiloxanes by alkaline or Acidic ring opening polymerization 2) Poly condensation of linear α,β-dihydroxy methyl siloxane oligomers

17. • Control of chain length( or viscosity) Addition of chain termination agents i.e. Trimethyl Siloxy-containing siloxanes (Hexamethyl disiloxane) or water ⊙ Alkaline Ring Opening Polymerization • Cyclic Poly(dimethyl siloxanes) (i.e. Octamethyl cyclotetrasiloxane) in the presence of KOH(10ppm) => Linear poly(dimethylsiloxane) with a broad molecular weight distribution and cyclic siloxanes of different ring sizes

18. ⊙ Acidic Ring opening polymerization • Ring opening polymerization of octamethyl cyclotetrasiloxane • equilibrium catalysts Sulfuric Acid Perfluoro alkyl Sulfonic acid Acid-activated clay particles • Advantageous for the manufacture of the low-viscosity and Si-H containing Poly(dimethylsiloxanes) * Removal of cyclic siloxanes possible by distillation after neutralizing the reaction product

19. ⊙ Non-equilibrating polycondensation • Polycondensation of α,β-dihydroxy methyl siloxane oligomers with OH-end groups at room temperature • Catalyst : Phosphonitrile dichloride (PNCl2)x, where x= • This reaction can be terminated by neutralization with amines

20. Manufacture of Branched Poly(organosilioxane)-silicone Resins • Two step manufacturing process ) Hydrolysis of a (chloro) organosilane mixture (methyl and phenyl groups) with the branching (trichloro) organosilanes proceeds in the presence of solvents (i.e. Xylene) and higher alcohols ) The Resulting hydrolysate with silanol or alkoxysilyl groups => Resins by thermal polymerization

21. 4. 4. Industrial Silicone products 4. 4. 1
4.4. Industrial Silicone products Silicone oils • Industrially most important silicone oil α,w-trimethylsilyl poly(dimethylsiloxanes) R (CH3)3Si-O-Si-O-Si(CH3) R n R/R : CH3/CH3, CH3/C6H5, C6H5/C6H5 or CH3/H

22. • Properties • pour point : -60~-35℃ • High stabilities to high temperature stress and oxidative degradation i.e. Silicon oil with phenyl groups Highest thermal stability Lifetime : months at 250℃ in air and 350℃ in closed system • Good electric insulating properties • Low surface tension • Odorless, tasteless and physiologically inert

23. • Applications • Heat transfer media • Lubricant • Hydraulic oil • Brake fluid • Transformer oil • Flow and Glow improvers in paint industry • Foam stabilizers in poly(urethane) foams • Defoaming agents in the crude oil industry • Hydrophobicity Cosmetics, Cars and furniture polishing

24. Products from silicone oils ⊙ Silicone oil emulsions produced from poly(dimethylsiloxane) or poly(hydrogen methylsiloxane) oils with trimethyl siloxy groups • Applications • Mold releasing and deaeration agents in the manufacture of tires • Hydrophobizing and bulking of fabrics in the textile industry • Antifoaming agents(silica containing emulsion)

25. ⊙ Silicone paste and Greases • Silicone paste manufactured by incorporating large quantities of highly dispersed silicas or calcium or lithium soaps • Sealants and specialty Greases Silicone Rubbers • product types ∽ crosslinking mechanism and application areas Room temperature vulcanizable single component silicone rubber

26. • Steps of Cross linking of single component Silicone rubbers 1) Reaction of a hydroxy group-terminating poly(dimethyl siloxane) with a hydrolyzable group-containing silane or siloxane crosslinking agent in the presence of fillers and a condensation catalyst

27. The above mixtures are stable in the absence of moisture But In the presence of moisture, the reactive groups are hydrolyzed

29. • Highly dispersed silicas as reinforcing filler 1~30 wt% incorporation to improve the mechanical properties. • Maximum 30% of trimethoxy-terminated Poly(dimethyl siloxane)silicone oil -> Pliant silicone Rubber • Sn-organic compound: Hardening process (condensation) • Room temperature vulcanizable single component silicone rubber used as -sealing compounds in the construction industry, sanitory sector, glass sector and automobile industry

30. - Adhesives for heat-resistant bonds and seals 4. 4. 3. 2
- Adhesives for heat-resistant bonds and seals Room Temperature vulcanizable two component silicone rubbers - Mixture of the polymer and the crosslinking component • Two different crosslinking systems i) Based on polycondensation ii) Polyaddition i) Polycondensation systems poly(dimethylsiloxane) with hydroxy end groups and a viscosity of 103 to 105 mPas is crosslinked with a crosslinking component containing tetraalkoxysilanes and a condensation catalyst

31. Tetra alkoxy silanes, i. e
Tetra alkoxy silanes, i.e. TEOS(crosslinking agent) Condensation Catalyst : Dibutyl tin dilaurate Therfore, a poly(dimethyl Siloxane) with hydroxy groups is corss-linked with TEOS an condensation
catalyst ii) Poly addition system Methyl vinyl Siloxy-Containing poly(dimethyl Siloxane) with trimethyl siloxy or dimethyl
vinyl siloxy end groups with a similar
viscosity

32. • Hydrosilation These polymer components react with hydrogen methyl siloxy-containing poly(dimethyl siloxane) having either trimethyl siloxy or hydrogen dimethyl siloxy end groups -> Crosslinking • Catalyst : Pt (H2Pt2Cl6)

34. Read Text Silicone Rubber Properties • Excellent thermal stability i.e. Elastomeric properties, very stable in hot air at 180℃ Mechanical properties at 180℃, as good as those at 25℃ ∴ Much better tensile strength at 180~200℃ than organic rubbers while 2~3 times the tensile strength of silicone rubber at room temperature

35. • Constant and high hardness down to -50℃ • Good chemical stabilities except for strong acids and bases and chlorine • Good insulators both at Room T. and higher T. • Electrically conducting with the incorporation of carbon black • Flame resistant and self-extinguishing by adding Pt.compound * Upon firing, No toxic products formed except for CO

36. Silicone Resins - Poly(organosiloxanes) w/t a high proportion of branched tri- or tetra-functional siloxy groups D D RSi-O3/2 Si-O4/2 • Hardening process of silicone resins subjecting liquid silicone resins or silicone resin solutions to several hours heating at 180~250℃ • Thermally stable coatings maintain their transparancy, gloss or elasticity even at 200~ ℃(phenyl group) • Hydrophobic and extremely weather resistant

37. Applications of methyl- or methylphenyl resins • Raw materials for paints, binders and building preservation • Electrically insulating lacquer (wire enamel) • Bonding of glass filaments or mica(운모) insulating materials •Corrosion-protection stoving enamel, pigmented w/t. Zinc dust • Enameling of metal chimney • Applications of silicone-polyester compound resins • Heat resistant stoving enamels for cooking and roasting utensils

38. • Heating apparatus and cookers • Coil coating of metallic plates for façade • Rendering plastics scratch resistant