Gelest Silicone Fluids - Gelest Inc.

More documents

Recommendations

Info

▲ ▲ ▲ ▲ Gelest, Inc. Properties of Conventional Silicone Fluids (Polydimethylsiloxanes) – continued Polydimethylsiloxane properties that do not vary signifcantly for fluids with viscosities greater than 10 cSt. are listed below. Reactivity While they exhibit low reactivity under many conditions, certain environments are destructive to silicone fluids. Hydrogen fluoride, for example, attacks the silicone-oxygen bond to produce dimethylsilyl fluorides and water, which generate corrosive gases. Strong bases such as methanolic potassium hydroxide destroy silicone fluids and create resinous byproducts. Thermal degradation at elevated temperatures causes rearrangement of the silicone-oxygen bonds to produce volatile byproducts. Free-radical reaction of the methyl groups to form cross-linked materials by oxidation with peroxy compounds increases fluid viscosity and causes the fluid to gel. Solubility of fluids Methylene chloride, chlorofluorocarbons, ethyl ether, xylene and methylethyl ketone are typical solvents for dimethylsiloxanes. Low viscosity polymers are also soluble in acetone, ethanol, dioxane and dihexyladipate. They are insoluble in methanol, cyclohexanol and ethylene glycol. The solubility parameter for 100 cSt. fluid is 7.4. Solubility of Gases Gas ml gas/ml liquid @25°C Nitrogen 0.16-0.17 Carbon Dioxide 1.00 Air 0.16-0.19 Hydrogen 0.11-0.12 Gaseous Permeability of Polydimethylsiloxane Gas P* x 10 9 H2 97 He 52 NH3 885 H20 5400 CO 51 N2 42 NO 90 02 90 H2S 1500 Ar 90 CO2 410 *cm 3 /s . cm 2 . cm Hg values adjusted from filled silicone membranes Gas P* x 10 9 N2O 650 NO2 1140 SO2 2250 CS2 1350 CH4 142 C2H6 375 C2H4 200 C2H2 3960 C3H8 615 n-C4H10 1350 n-C5H12 3000 Gas P* x 10 9 n-C6H14 1410 n-C8H18 1290 n-C10H22 645 HCHO 1665 CH3OH 2085 COCI2 2250 Acetone 835 Pyridine 2865 Benzene 1620 Phenol 3150 Toluene 1370 Thermal Specific heat 0.35-0.37 cal/gm/°C Heat of formation -2.41 Kcal/gm Heat of combustion (>50 cSt.) 6.13 Kcal/gm Glass transition temperature -128°C Gel time, 150°C indefinite Gel time for intermediate viscosity fluids, 200°C 200 hours Gel time for high viscosity fluids, 200°C 100 hours Autoignition temperature greater than 460°C 12 MANUFACTURERS OF SILANES AND SILICONES
▲ ▲ ▲ ▲ Gelest, Inc. Rheological Behavior Under Shear At shear rates commonly encountered (≤10 4 s -1 ) polydimethylsiloxanes behave, at viscosities up to 1,000 cSt., like Newtonian fluids. Viscosity is constant and independent of the velocity gradient. Apparent viscosity is identical with viscosity extrapolated to zero velocity gradient. For oils of a higher viscosity than 1,000 cSt., this ratio is only constant for velocity gradients below a certain value. Beyond this value, becoming lower as the product becomes more viscous—the ratio is no longer constant: apparent viscosity falls below real viscosity (extrapolated for a zero velocity gradient) and the behavior is then known as “pseudoplastic.” This change is perfectly reversible, and behavior again becomes Newtonian when the velocity gradient falls once more below the critical value. Viscosity returns to its initial level even after intense shearing of long duration. As a guide, the table indicates the “critical” velocity gradients for polydimethylsiloxanes (where change of rheological behavior occurs) as well as apparent viscosity measured at velocity gradient equal to 10,000 s -1 . CH3 CH3 Si CH3 O CH3 Apparent viscosity for a velocity gradient Critical velocity of 10,000 s -1 gradient (s -1 ) (in cSt.) 1,000 2,500 850 12,500 200 4,700 30,000 150 6,000 100,000 30 8,200 Si CH3 O n CH3 Si CH3 CH3 Apparent viscosity as a function of velocity gradient Viscosity in cSt. 2,000,000 1,500,000 500,000 200,000 100,000 50,000 20,000 10,000 5,000 2,000 1,000 2,500,000 500,000 200,000 100,000 60,000 30,000 20,000 12,500 10,000 5,000 2,000 1,000 500 Temperature 25°C 0.1 0.2 0.3 1 2 5 10 20 50 100 200 500 1,000 2,000 5,000 20,000 100,000 500,000 10,000 50,000 200,000 1,000,000 VELOCITY GRADIENT (s -1 ) (215) 547-1015 FAX: (215) 547-2484 13
Page 2 and 3: SILICONE FLUIDS Property Profile Gu
Page 4 and 5: ▲ ▲ ▲ ▲ Gelest, Inc. Relate
Page 6 and 7: ▲ ▲ ▲ ▲ Gelest, Inc. DEFINI
Page 8 and 9: ▲ ▲ ▲ ▲ Gelest, Inc. Silico
Page 10 and 11: ▲ ▲ ▲ ▲ Gelest, Inc. Conven
Page 12 and 13: ▲ ▲ ▲ ▲ Gelest, Inc. Proper
Page 16 and 17: ▲ ▲ ▲ ▲ Gelest, Inc. Low Vo
Page 18 and 19: ▲ ▲ ▲ ▲ Thermal Silicone Fl
Page 20 and 21: Organic Compatible Silicone Fluids
Page 22 and 23: ▲ ▲ ▲ ▲ Gelest, Inc. Hydrop
Page 24 and 25: ▲ ▲ ▲ ▲ Gelest, Inc. Low Te
Page 26 and 27: ▲ ▲ ▲ ▲ Gelest, Inc. Append

Gelest Silicone Fluids - Gelest Inc.

Create successful ePaper yourself

Delete template?

Save as template?