Polyurethanes Silane

Effete of silanes on bond strength of polyurethane coatings... 

Microgels have been also synthesized using isocyanates or polyurethanes [355,356] and by polycondensation of silanes [357-360]... 

Preparation of model compounds and polyurethanes. A procedure for the preparation of the non-silicon containing monocarbamate and biscarbamate models has been reported previously (8). In order to obtain the silicon containing model compound, 5.0 g of bis(4-aminophenyl) dimethyl silane [synthesized according to Pratt, et.al (9)] was added to 7.0 g ethyl chloroformate at room temperature. A salt immediately formed. The mixture was refluxed for 15 min. The solution was then cooled, vacuum filtered, and recrystallized from ethanol to yield 1.0 g of a white powder MP 162-3 °C Anal. c20H26°4N2Si Calc. C, 62.17 H, 6.70 N, 7.23 Found C, 62.01 H, 6.79 N, 7.42. 

Polyurethane hydrogels derived from UV curable urethane prepolymer and hydrophilic monomers were prepared and their properties were evaluated. The urethane prepolymer used in this study contained well-defined hard segments centered with a polyether-based soft segment and end-capped with methacrylate groups. The hydrophilic monomers studied were 2-hydroxyethyl methacrylate (HEMA), N-vinyl pyrrolidone, and glycerol methacrylate. Methacryloxypropyl tris(trimethysiloxy) silane (TRIS) was also used in some cases to modify properties. All compositions were UV... 

Abstract— The use of organosilanes as adhesion promoters for surface coatings, adhesives and syntactic foams is described and reviewed in the light of published work. Data are presented on the beneficial effect of silanes, when used as pretreatment primers and additives, on the bond strength of two pack epoxide and polyurethane paints applied to aluminium and mild steel. It is shown that silanes when used as additives to structural epoxide and polyurethane adhesives are less effective than when used as pretreatment primers on metals but are highly effective on glass substrates. The compressive properties of glass microballoon/epoxide syntactic foams are shown to be markedly improved by the addition of silanes. 

The effect of silanes on the bond strength of a two-pack polyurethane paint Direct pull-off, silane on surface... 

Reference to Table 7 will show the data for the two-pack polyurethane paint, and indicate a similar improvement to that of the epoxide paint due to the use of silanes. Although there are differences in the values for particular silanes on the different substrates and surface treatments, the general picture is that AAMS and MPS are the most effective in epoxide and polyurethane paints. 

Although not reported here the silanes used in conjunction with the epoxide and polyurethane paints were largely ineffective with the oxidative cure systems. 

A similar set of curves is shown in Fig. 2 for the polyurethane paint. Here again the non-silane control lost most of its bond strength in the first 3 days and the loss was continuing after 15 days. The paint containing MPS and the AAMS treated surface equilibriated after 7 days. 

As it had been shown that silanes were effective as pretreatments for a variety of coatings and particularly so when used as additives, selected silanes were examined as pretreatments and additives in conjunction with a two pack polyamide cured epoxide adhesive (Epikote 828/Versamid 115, 1/1) and a structural polyurethane adhesive based on diphenylmethanediisocyanate and a polyester resin. 

Reference to Table 12 will show the data for the structural polyurethane adhesive, from which it can be seen that the pattern for the epoxide adhesive is almost repeated, with all the silanes used as pretreatments producing marked... 

Comparison of silanes as pretreatments and additives for a rigid polyurethane adhesive Butt tensile, grit-blasted metal, 2 wt% as pretreatment and additive... 

It seems less likely that MAMS is reactive towards either epoxide or isocyanate groups. In spite of this MAMS performed well, in some cases, notably the polyurethane paint on mild steel and aluminium, see Tables 3 and 7, better than ECMS and APES. Clearly chemical reaction is not a prerequisite for bond strength enhancement. Chain tangling, simple physical effects, may play an important role with both MPS and MAMS and possibly other silanes. 

Blends of 10% aminosilane F and 90% hydrophobic silanes, i.e. vinylsilane A, chloropropylsilane B, methylsilane G, and phenylsilane I, gave superior adhesion of three types of polyurethane (RIM, thermoplastic, and one-component rigid) to glass compared with aminosilane F alone. Table 3 shows that the blend with phenylsilane I gave the best adhesion overall to all three polyurethanes after 5 h in boiling water. This improved performance is attributed to the enhanced hydrophobicity of the interphase region which is conferred by the replacement of most of the hydrophilic aminosilane with hydrophobic silane. 

Figure 7.6 Schematic representation of hard clusters in (a) a polyurethane network composed of a long diol, a triol, and a diisocyanate (polyaddition reactions, Chapter 2). (b) a hybrid inorganic-organic network composed of a silane end-capped long diol (polycondensation reactions, Chapter 2).

Polyurethane Methanol 1. Abrasion followed by brushing. Grit or vapor blast or 280-grit emery cloth followed by solvent wipe. 2. Incorporation of a chlorosilane into the adhesive elastomer system 1% by weight is usually sufficient. Chlorosilane is available commercially. Addition to adhesive eliminates need for priming and improves adhesion to glass and metals. Silane may be used as a surface primer... 

Pohl, E. and Osterholz, F. D., Novel Vulcanizable Silane-Terminated Polyurethane Polymers, U.S. Patent 4,645,816, 1987. 

This chapter is organized as follows. Section 4.2 addresses the study of photoisomerization and photoinduced orientation of azobenzene molecules at the molecular level in SAMs of azo-silane molecules. Section 4.3 discusses photoinduced effects in supramolecular assemblies, i.e., LBK multilayer structures containing azobenzene molecules, and compares the photoinduced movement of azobenzenes in these structures to that observed in spin-cast films. Section 4.4 focuses on the isomerization and sub-Tg photoinduced orientation in a series of very high Tg (up to 350°C) nonlinear optical polyimide and thermoplastic donor-embedded polyurethane polymers containing azo dye, especially focusing on polymer structure-Tg-photoinduced molecular movement relationships. Section 4.5 describes pressure effects on photoisomerization and photo-orientation in films of a PMMA polymer containing azo dye. Finally, we make some concluding remarks in Section 4.6. 

One-component polyurethane sealants are based on a polyether or polyester isocyanate prepolymer end-capped with a room-temperature-curable group such as trialkoxy silane. Free isocyanate groups are not used in one-part systems because carbon dioxide is evolved on reaction with moisture from the atmosphere which results in bulging of the sealant in the joint. 

Furthermore, it is conceivable to use standard chain elongation techniques, e.g., with diisocyanates known from polyurethane chemistry, to adjust the viscosity of the HO-P-OH polymers prior to the derivatization with the isocyanatomethyl-dimethylmonomethoxy silane This of course also influences the mechanical properties of the vulcanizates. 

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