Silanes, aminofunctional

Ishida, H., Chiang, C.H. and Koenig, J.L. (1982). The structure of aminofunctional silane coupling agents. Polymer 23, 251-262. 

High surface area fumed silica (about 99.8% SiOz), Cab-O-Sil grade M5, was donated by Cabot Corp. (Tuscola, IL). It was reported, and verified by N, adsorption, to have a surface area of 200 m2/g. The silica was heated to about 120°C for at least 24 h under vacuum before use, which did not change the surface area. Distilled acetone and water were used as solvents for the coupling agents. Acetic acid and hydrochloric acid were used as catalysts for the non-aminofunctional silane coupling agents. 

Non-aminofunctional silanes did not show an observable methanol resonance after about 5-6 h when no catalyst was added. This suggests that hydrolysis was very slow under these conditions. An acid was added to aid in the hydrolysis of MPS, VS, GPS, and MrPS. The results show that the rate constant increases with a decrease in the pH of the solution, similar to previously reported results [16, 47]. The addition of HC1 also significantly increased the reaction rates, as reported by Pohl and Osterholtz for the hydrolysis of GPS in water [16]. 

Figure 1. (a) Polymeric aminofunctional silane-carrying dialkoxy silane groups, (b) Multiple sawhorse -type siloxane bonding to the fiber surface. 

Thus, in alkyd, polyester, and epoxy coatings applied to CRS, phosphatized steel, and aluminum, the use of ZAs APG (aminofunctional) and CPG (carboxy-functional) has allowed for the virtual elimination of blister formation and corrosion after 300 h of salt fog exposure. The use of multifunctional ZAs in a Kraton base adhesive has allowed for a 52% increase in T-peel strength on EPDM rubber when compared with the same adhesive containing aminofunctional silane. Incorporation of mercaptofunctional ZA into crosslinkable elastomers has... 

For example, an aminofunctional silane can condense almost instantaneously after hydrolysis due to the high pH of the amine group, leading to a kinetically controlled structure which is thermodynamically unequilibrated. Provided that a sufficiently high concentration was used, the solution turns into a gel. With time, in the presence of water, the catalytic action of the amine reorganizes the siloxane structure by rehydration and condensadon reactions, and redissolves the silane. Thus, the time factor is also important when silane stmctures are to be studied. 

Aminosilanes of the general formula R Si(NH2)4- , R Si(NHR)4 , R Si(NR2)4- are prepared by the reaction of silicon hydrides or chlorosilanes with ammonia or other amines in the presence of an inert solvent. These hydrosilylation reactions may be carried out at room temperature, with the reaction products being isolated by simple phase separation (3,46-48). To obtain the MD D M type aminofunctional siloxanes typically employed in personal care formulations, aminofunctional silanes (generally aminoethylaminopropyltri-methoxysilane or y-aminopropyltrimethoxysilane) may be polymerized with linear hydrolysates or with octamethylcyclotetrasiloxane to form aminofunctional silicone fluids. Nucleophilic substitution and redistribution reactions have also been used to prepare one modified silicone from another. For example, aminofunctional siloxanes may be prepared by substitution as illustrated in Eq. (4). 

Some pressure-sensitive tapes including surgical tapes have been reported to contain carboxylic acrylate copolymers. A pressure sensitive tape consisting of foil, polyester, polyolefin, or acrylic adhesive layer and a car-boxylated polymer-aminofunctional silane primer layer has been patented. The silane alone is reported to interfere with adhesion of the tape to the substrate but excellent adhesion is obtained if a carboxylated EVA copolymer is added to the primer. 

Figure 6. Comparison of the ultimate fiber fragment aspect ratio in SFC specimens prepared from treated and untreated fibers under the dry condition (I) untreated (2) APS 3-aminopropyltricthoxy-silane (3) PS076.5 dimethoxymclhylsilylpropyl-substituicd polyelhylcneimine (aminofunctional) (4) PS076 trimethoxysilylpropyl-substitutcd polyelhylcneimine (aminofunctional).

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