Other Alkyl Silicone Resins

Propyl, butyl, and amyl silicones of the type (R2SiO)x are colorless oily liquids which resemble ethyl silicone in appearance. The cor- 

26 Martin and Kipping, J. Chem. Soc. 95, 313 (1909), report that in one case a soft gel was obtained from diethyl silicone oil, but that the result could not be repeated, 

The higher alkyl silicones also oxidize more readily than do the lower members of the series. The ease with which an alkyl group may be removed from the siloxane chain by oxidation can best be measured by the time the polymer takes to crumble and disintegrate when heated in air at a given temperature. Methyl silicone may have a life equivalent to some 10 years of service at 200° C., whereas amyl silicone cracks and checks after a day at 200°. 

Although it contains an aromatic nucleus, benzyl silicone is correctly classed as an alkyl silicone, because the phenyl group is attached through a —CH2— group to the silicon. Moreover, benzyl silicone resembles all the previously described alkyl silicones in that the complex polymeric mixture from the condensation of dibenzylsil-anediol is an oil30 and not a resin. Chemically, the benzyl group 

Cyclohexyl silicone resembles benzyl silicone quite closely. Compositions of the type (CeHnSiOi.g) are gluelike in consistency, as Kipping described them, and they may be converted to ether-insoluble resins.34 Almost all chemical manipulations of the lower polymeric forms result in conversion of these into more of the gluelike higher polymers. 

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Silicone paints are formed by controlled hydrolysis and condensation of alkyl alkox-ysilanes, and may be encountered either alone or in formulations with other synthetic resins. The typical structural unit in the polymer chain is dimethyl siloxane, and pyrolysis of such resins takes place with random chain scission and the extended formation of stable cyclic fragments. In Figure 12.14 the pyrogram of a silicone resin is shown, with cyclic siloxane oligomers eluting at the shorter retention times, followed by the linear siloxane fragments. 

Tospearl is a spherical silicone resin particle made by the controlled hydrolysis and condensation of alkyl trialkoxysilanes (equation 1) and produced by Toshiba Silicones, a joint venture of GE Silicones. The first report of these materials appeared in 1985 when the aqueous amine catalyzed condensation of methyl trimethoxysilane was described (1). Since the initial disclosure, a number of other patents have issued in this area (2-8). The product is a tluee-dimensional network that is intermediate between inorganic and organic particles. This paper describes the physical and chemical properties of this network as well as its utility in a number of applications. 

This is a very diverse group of polymeric materials. Particles have mostly spherical form. Spherical silicone resin (commercial name - Tospearl) is produced in several grades, most of which are spherical (some are elongated and irregular). Controlled hydrolysis and condensation of alkyl trialkoxysilane permits tight control of properties." Particles of some grades are monodisperse, containing only a small admixture of particles of other sizes than attempted in s mthesis. 

The chemistry of silicone halides was recently reviewed by Collins.13 The primary use for SiCU is in the manufacturing of fumed silica, but it is also used in the manufacture of polycrystalline silicon for the semiconductor industry. It is also commonly used in the synthesis of silicate esters. T richlorosilane (another important product of the reaction of silicon or silicon alloys with chlorine) is primarily used in the manufacture of semiconductor-grade silicon, and in the synthesis of organotrichlorosilane by the hydrosilylation reactions. The silicon halohydrides are particularly useful intermediate chemicals because of their ability to add to alkenes, allowing the production of a broad range of alkyl- and functional alkyltrihalosilanes. These alkylsilanes have important commercial value as monomers, and are also used in the production of silicon fluids and resins. On the other hand, trichlorosilane is a basic precursor to the synthesis of functional silsesquioxanes and other highly branched siloxane structures. 

In some cases, there may be fewer than two alkyl groups attached to each silicon atom so that other oxygen bridges form between chains. These polymers are known as silicones, and they are used as lubricants, oils, and resins. 

Resinous silicones such as trimethylsiloxysilicates act as effective substantivity additives alone and in combination with other silicones such as high-molecular-weight dimethicone gums. In skin care evaluations, the number of water wash cycles required to remove a silicone barrier was shown to increase markedly with the addition of an MQ or siloxysilicate resin (92). In other studies, it has been demonstrated that modification of the siloxysilicate resin with alkyl and ester functionality increased the resistance to water washoff even further (163). The water-resistant properties of these materials have also been demonstrated to be dependent upon other ingredients in the formulation (182). 

Some specific recent applications of the GC-MS technique to various types of polymers include the following PE [49,50], poly(l-octene) [51], poly(l-decene) [51], poly(l-dodecene) [51], 1-octene-l-decene-l-dodecene terpolymer [51], chlorinated polyethylene [52], polyolefins [53, 54], acrylic acid methacrylic acid copolymers [55], polyacrylates [56], styrene-butadiene and other rubbers [57-59], nitrile rubber [60], natural rubbers [61, 62], chlorinated natural rubber [63, 64], polychloroprene [65], PVC [66-68], silicones [69, 70], polycarbonates [71], styrene-isoprene copolymers [72], substituted PS [73], polypropylene carbonate [74], ethylene-vinyl acetate copolymers [75], Nylon [76], polyisopropenyl cyclohexane a-methyl styrene copolymers [77], m-cresol-novolac epoxy resins [78], polymeric flame retardants [79], poly(4-N-alkyl styrenes) [80], polyvinyl pyrrolidone [81], vinyl pyrrolidone-methyl acryloxysilicone copolymers [82], polybutylcyanoacrylate [83], polysulfide copolymers [84], poly(diethyl-2-methacryloxy)ethyl phosphate [85], ethane-carbon monoxide copolymers [86], polyetherimide [87], bisphenol A [88], ethyl styrene [89], styrene-isoprene block copolymer [89], polyvinyl alcohol-co-vinyl acetate [90], epoxide thiol [91], maleic acid-propylene copolymer [92], P-hydroxy butyrate-P-hydroxy valerate copolymer [93], polycaprolactams [39,94], PS [95,96], polypyrrole [95,96], polyhydroxy alkanoates [97], poly(p-chloromethyl) styrene [81], polybenzooxazines and siloxy substituted polyoxadisila-pentanylenes [98,99] poly benzyl methacrylates [100], polyolefin blends after ageing in soil [101] and polystyrene peroxide [43]. 

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