Chemistry urethane

Urethanes. The basis for urethane chemistry is the reaction of an isocyanate group with a component containing an active hydrogen. 

Over 40 chemical reactions are used in urethane chemistry. The six most common urethane reactions that are relevant to adhesives are shown in Fig, 1. The monomeric forms of the reactions are shown for simplicity s sake however, most commercially useful products for polyurethanes are based on polyfunctional isocyanates and polyfunctional alcohols or polyols . 

Liquid organic rubbers with reactive functionality can be prepared by several methods. End-functional oligomers are preferred. Chains attached to the network at only one end do not contribute as much strength to the network as those attached at both ends [34], Urethane chemistry is a handy route to such molecules. A hydroxy-terminated oligomer (commonly a polyester or a polyether) can be reacted with excess diisocyanate, and then with a hydroxy methacrylate to form a reactive toughener [35]. The methacrylate ends undergo copolymerization with the rest of the acrylic monomers. The resulting adhesive is especially effective on poIy(vinyl chloride) shown in Scheme 2. 

I. S. Bechara, The Mechanism of Tin-Amine Synergism in the Catalysis of Isocyanate Reaction with Alcohols, in Urethane Chemistry and Applications, ACS Symposium Series 172, K. N. Edwards, (Ed.), American Chemical Society, Washington, DC, 1981. 

In a specific example of adhesive bonds between cold rolled steel and SMC adherends (Table II) an adhesive based on hydrolysis resistant epoxy chemistry (i.e., adhesive E) was compared with an adhesive based on hydrolysis prone urethane chemistry (i.e., adhesive C) in composite to cold rolled steel bonds. After corrosion testing, a significant difference in both retention of initial bond strength and locus of failure was observed. For bonds prepared with adhesive E, little if any reduction of the initial bond strength was observed after corrosion testing. The locus of failure for both the tested and untested bonds was largely in the... 

Urethanes. The basis for urethane chemistry is the reaction of an isocyanate group with a component containing an active hydrogen. The first step in formulating a urethane sealant is to prepare what is commonly called (lie prepolymer, typically by reaction of a hydroxy-terminated polyether with a stoichiometric amount of a diisocyanate. 

Initial commercial developmental work on polyurethanes was carried out in Germany between World War I and World War II to find an alterative to nylon, which had been developed by E. I. du Pont de Nemours Company. The research was based on urethane chemistry. 

The study of industrial applications of isocyanate chemistry and polymers derived from isocyanates received much attention in Europe, particularly Germany, in the 1930s and during World War II. Patents on aspects of urethane chemistry appeared as early as 193755 jhg effort going into understanding isocyanate chemistry and commercializing urethane products continues.56-60... 

Sometimes the system is formulated so that multiple cure mechanisms are possible and can occur sequentially or simultaneously. Compositions that rely on both epoxy and urethane chemistry are examples.62,94,95 These are compositions containing the diglycidyl ether of bisphenol A, an isocyanate or isocyanate-terminated prepolymer, amines or other reactants for either epoxy or isocyanates, and catalysts. 

Polyurethane Foam Polyester Fiber Products Urethane Chemistry Research Consulting Upholstery Cushion Materials Memory Foam... 

Describe how urethane chemistry can be used to make both flexible and rigid foams.. ... 

In general, polishing pads are composed of either a matrix of cast polyurethane foam with filler material to control hardness or polyurediane impregnated felts. Polyurethane is utilized because urethane chemistry allows the pad characteristics to be tailored to meet specific mechanical properties needs. Jairath et al. describe the manufacture of pad material as follows ... 

Dow Chemical Company Form No. 109-598-84. Polyether Polyol Voranol and General Urethane Chemistry (1984)... 

In coating applications, urethane chemistry is used to cross-link coatings and also to prepare thermoplastic polyurethanes or isocyanate-terminated pre-polymers. 

In 1979 the Macromolecular Secretariat of the American Chemical Society agreed that a symposium on Urethane Chemistry and Applications was of broad and current interest and that such a symposium met the requirements of being topical to all of the member divisions of the Secretariat. As a result, this symposium was scheduled for 1980, and a group of specialists representing each of the member ACS Divisions, as well as the Division of Chemical Marketing and Economics, was recruited. These individuals subsequently became the associate editors of this book. 

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