Silane organofunctional

Organofunctional silanes are used to promote polymer-to-filler bonding with clay or siHca fillers. Vinyl silanes are used in peroxide-cured wire insulation to promote stronger bonding with calcined clay fillers. Mercapto silanes are used to treat kaolin clay in sulfur-cured compounds. 

Fig. 3. Synthetic routes to some common organofunctional silanes.

Oxane bonds, M—O—Si, are hydroly2ed during prolonged exposure to water but reform when dried. Adhesion in composites is maintained by controlling conditions favorable for equiUbrium oxane formation, ie, maximum initial oxane bonding, minimum penetration of water to the interface, and optimum morphology for retention of silanols at the interface. The inclusion of a hydrophobic silane, such as phenyltrimethoxysilane [2996-92-17, with the organofunctional silane increases thermal stabiUty of the silane and make the bond more water resistant (42). 

Performance of coupling agents in reinforced composites may depend as much on physical properties resulting from the method of appHcation as on the chemistry of the organofunctional silane. Physical solubiUty or compatibiUty of a siloxanol layer is determined by the nature and degree of siloxane condensation on a mineral surface. 

Organofunctional silane Chemical structure of organofunctional group Functional groups used... 

These inorganic polymers can be copolymerized with organofunctional silanes to modify the physical properties or to include specific reactive functionalities to... 

Brandhuber, D., Peterlik, H. and Husing, N. (2005) Simultaneous drying and chemical modification of hierarchically organized silica monoliths with organofunctional silanes. Journal of Materials Chemistry, 15, 3896-3902. 

The synthesis of organosilicones and organosilicone surfactants has been well described elsewhere [36-39] and hence only a brief review is given here. Industrially the manufacture of silicones is performed stepwise via the alkylchlorosilanes, produced through the reaction of elemental silicon with methyl chloride (the Muller—Rochow Process) [40,41]. Inclusion of HC1 and/or H2(g) into the reaction mixture, as in Eq. (1.2), yields CH3HSiCl2, the precursor to the organofunctional silanes, and therefore the silicone surfactants ... 

The subject of silane chemistry and its interaction with both glass surface and polymer resins have been studied extensively. Since the silane coupling agent for improving the bond quality has first appeared in the literature (Rochow, 1951), a wide variety of organofunctional silanes has been developed, prominently by Plueddemann and coworkers. An early compilation of this subject for epoxy and polyester matrix composites (Plueddemann et al., 1962, Clark and Plueddemann, 1963 Plueddemann, 1974), and more recent reviews on the use of silane agents and... 

Oulwaler.. 1.0. (1956). In Proc. lilt Annual Tech. Conf. Reinforced Plastics Div. SPI Sec. 9-B. Plucddemann, E.P. (1972), Cationic organofunctional silane coupling agents. In Proc. 27th Annual Tech. Conf. Reinf Plastic. SPI, Section 21-B. 

Covalent immobilization methods of NAs to a silica surface require its chemical modification. Functionally inert surface silanols (Si - OH) need to be transformed into reactive species to which the NAs can be attached irreversibly. To date, the main method for the attachment of biological moieties to silica surfaces has involved substrate reaction with organofunctional silanes of the general structure (RO)3Si(CH2)X, followed by the covalent attachment of the biological molecule to the newly introduced fimctional group on the surface [31,32]. Examples of organofimctional silanes used this way include (3-glycidoxypropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane,... 

Spectroscopic techniques are extremely useful for the characterization of filler surfaces treated with surfactants or coupling agents in order to modify interactions in composites. Such an analysis makes possible the study of the chemical composition of the interlayer, the determination of surface coverage and possible coupling of the filler and the polymer. This is especially important in the case of reactive coupling, since, for example, the application of organofunctional silanes may lead to a complicated polysiloxane interlayer of chemically and physically bonded molecules [65]. The description of the principles of the techniques can be found elsewhere [15,66-68], only their application possibilities are discussed here. 

Electron beam irradiation is one of the methods of cross-linking in fhis process. The other methods use peroxide, multifunctional azide, or an organofunctional silane. Polyethylene resins respond to electron beam irradiation well since the rate of cross-linking exceeds significanfly fhe chain scission. Polypropylene (PP) is prone to P-cleavage, which makes if difficult to cross-link by a free radical process. For fhaf reason, PP resins... 

I was fortunate as an industrial scientist for Plaskon and Dow Corning to be allowed to concentrate for over 40 years on organofunctional silanes and their applications in surface modification of minerals. I chose a scientific ladder rather than an administrative ladder, so I could stay in the laboratory with one or two assistants and develop a practical feel for polymer composites. Understanding of interfacial phenomena was helped immensely by academic workers such as Professors Koenig and Ishida at Case Western Reserve University and Professor Boerio at the University of Cincinnati. They and their students conducted extensive analytical studies of the interface to demonstrate the reality of some of the concepts I had proposed from indirect evidence of performance tests. 

Aliphatic organofunctional silanes recommended as coupling agents for glass-reinforced polyesters, epoxies, or phenolics have heat stabilities of typical aliphatic organic chemicals and are not at all comparable to the methyl or phenyl silicones found in silicone polymers and resins. 

Abstract—A review of the literature is presented for the hydrolysis of alkoxysilane esters and for the condensation of silanols in solution or with surfaces. Studies using mono-, di-, and trifunctional silane esters and silanols with different alkyl substituents are used to discuss the steric and electronic effects of alkyl substitution on the reaction rates and kinetics. The influences of acids, bases, pH, solvent, and temperature on the reaction kinetics are examined. Using these rate data. Taft equations and Brensied plots are constructed and then used to discuss the mechanisms for acid and base-catalyzed hydrolysis of silane esters and condensation of silanols. Practical implications for using organofunctional silane esters and silanols in industrial applications are presented. 

In this review, we will briefly discuss selected literature on hydrolysis and condensation reactions at silicon which are relevant to organofunctional silanes. Some studies will involve simpler (lower functionality) models some may involve related chemical reaction classes illustrating a mechanistic point. We will then discuss selected references focused on silanes of the types used as coupling agents and crosslinkers. Finally, some reactions at the interface will be mentioned. 

One approach to this problem has been to characterize the practical consequences of silane hydrolysis. Visual observation of the hydrolysis behavior of typical organofunctional silanes, supplemented by some spectroscopic data, and trapping of silanols with trimethylsilanol were reported by Plueddemann [ 1, 14], Comparative data give some measures of the ease of hydrolysis and the solution stability. The data are quite helpful in the practical use of hydrolyzed silane solutions. They are not presented in a way that allows quantitative kinetic conclusions. 

A critical concern in the use of organofunctional silanes is the effects that the organofunctional groups and the silane ester groups have on the hydrolysis reactions occurring at silicon. 

Condensation of silanes is second order in silane concentration. Doubling the concentration of silanol species multiplies the rate of formation of condensed products by four-fold. To minimize condensation, aqueous solution concentrations of silanols below 1% by weight of typical organofunctional silanes should be used. 

Some interesting features of organofunctional silanes containing thiol groups have been documented at various times. The first report of silanes in this class... 

Salient considerations for the design of the molecular structure and conditions of application for organofunctional silane coupling agents include the following... 

Organofunctional silanes as adhesion promoters direct characterization of the polymer/silane interphase... 

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