DEVELOPMENT OF SILICONE RUBBERS FOR USE AT TEMPERATURES DOWN TO -100 F
Abstract
Several materials were evaluated as reinforcing pigments for G. E. SE-76 silicone rubber. Celite 318 and Perlite were poor when used alone. Burgess iceberg pigment, a calcined Al silicate, was moderately effective at higher loadings. A fine form of Mg trisilicate inhibited Bzsub2Osub2 curing. Micalith G, a finely divided graphitic mica, gave a cured silicone rubber of low strength but of a leathery nature. Si-O-Lite produced a material with 450-psi tensile strength with SE-76 gum. Hi-Sil 52-WHB-42 gave over 750 psi at a 20-volume loading. Du Pont GS199S silica possessed curing and reinforcing properties. The physical properties obtainable with SE-76 depended strongly on slight viscosity variations, particularly with the GS silica curing system. The variation in SE- 76 may be associated with its degree of polymerization and consequent change in average molecular weight. Coating the better reinforcing fillers (Titanox RANC, Santocel C, Hi-Sil) with 0.2 to 100 wt-% of a low-molecular-weight silicone oil improved their mixing and wettability with silicone gum. With the GS silica as a simultaneous curing and reinforcing pigment in the absence of Bzsub2Osub1, stocks of 1800-psi tensile strength and 800% elongation at a 64 Shore-A harness were produced with SE-76. With a small amount of Bzsub2Osub2, the strength was raised to 1900 psi and the elongation to 850% at a 73 Shore-A hardness. The best rubber stocks were obtained between a 15- and 25- volume loading; at a maximum loading of 50 volumes, a hard semiflexible resinous material of good dielectric properties was obtained.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 04, 1952
- Accession Number
- AD0002607
Entities
People
- B. J. Humphrey
- F. L. Kilbourne Jr.
- Harry H. Wasserman