Organosilicon grease-like compounds having good shear stability and being suitable for optical coupling are prepared by mixing a phenylmethylpolysiloxane fluid or a trimethylsiloxy endblocked fluid consisting of decylmethylsiloxane, tetradecylmethylsiloxane and alpha-methylstyrenemethylsiloxane units, a finely divided silica, and a polyalkylene oxide. A typical compound would be a mixture of 150 parts of a phenylmethylpolysiloxane, 15.5 parts of a fume silica having surface area of 380 square meters per gram, and 4 parts of polypropylene oxide having a molecular weight of 2,000. Such a compound has a light transmission in excess of 80% and excellent work shear stability.
There are described an immersion oil containing one or more compounds of the formula ##STR1## wherein R is hydrogen or methyl, and its use in optics, especially fluorescence microscopy.
The silicone grease composition is highly light-transmitting and very stable with little oil separation. The grease composition is compounded with (a) a methyl phenyl polysiloxane having a specific phenyl content, (b) a fumed silica filler having a specific surface area of at least 130 m.sup.2 /g and (c) an alkoxy-containing organosilane compound such as vinyl trimethoxy silane, 3-methacryloxypropyl trimethoxy silane, dimethyl dimethoxy silane and the like in a specified proportion.
The coated optical fiber of the invention is prepared by providing a coating layer of an ultraviolet-curable organopolysiloxane or a composition comprising the same and irradiating the coating layer with ultraviolet. Specifically, each of the terminal silicon atoms of the organopolysiloxane, which preferably has a linear molecular structure, has two or more ethylenically unsaturated polymerizable groups bonded thereto through an oxygen atom, such as CH.sub.2 .dbd.CHCOOCH.sub.2 CH.sub.2 --, [CH.sub.2 .dbd.C(CH.sub.3)COOCH.sub.2 ].sub.3 C--CH.sub.2 --and (CH.sub.2 .dbd.CHCOOCH.sub.2).sub.2 C(C.sub.2 H.sub.5)CH.sub.2 --. By virtue of this unique molecular structure of the organopolysiloxane, the coating layer is rapidly cured by ultraviolet irradiation to give a cured coating layer exhibiting very low water absorption and small temperature dependency of the Young's modulus at low temperatures.
A novel dilatant fluid which keeps fluid state within a broad temperature range, is excellent in storage stability, has large mechanical strength and shows large changing quantity of viscosity resistance accompanied by the increase of shear stress. It was found that excellent dilatancy is expressed markedly specifically in a composition comprising (B) from 0.5 to 100 parts by weight of a particle dispersing agent and (C) from 5 to 1,000 parts by weight of a silicone medium, based on (A) 100 parts by weight an inorganic fine particle having a primary particle size of from 2 nm to 30 .mu.m.
Fiber optic waveguides exhibiting a blackout phenomenon can be used for temperature sensing. A temperature sensing waveguide can be used in such applications as maintaining a material within a selected temperature range, freeze protection, viscosity control of liquids in pipelines, leak detection of cryogenic fluids, fire detection, application of heat-recoverable materials, and fluid level detection. Novel waveguides exhibiting blackout at selected temperatures for use in these applications are described. Among the novel waveguides are those having a cladding comprising a polyalkylphenyl siloxane and those having a cladding comprising a cross-linked polymethylalkyl siloxane. Also described are waveguides where only a section of the waveguide exhibits blackout and methods for making such waveguides.
