Condensation reactive molding

Polyurethanes are useful in numerous applications such as reaction injection molding, rigid and flexible foams, coatings and adhesives. However, due to the high reactivity of the isocyanate group [96], yielding either dimers, via self-condensation or a carbamate via the reaction with an alcohol, the A,jB-monomers have to be produced in-situ in the reaction vessel. 

Fig. 13.42 Simulation results of the RIM process involving a linear step polymerization T0 = Tw = 60°C, kf— 0.5L/moles, t(lii = 2.4 s. (a) Conversion contours at the time of fill, (h) Temperature contours at the time of fill. [Reprinted hy permission from J. D. Domine and C. G. Gogos, Computer Simulations of Injection Molding of a Reactive Linear Condensation Polymer, paper presented at the Society of Plastics Engineers, 34th Armu. Tech. Conf, Atlantic City, NJ, 1976. (Also published in the Polym. Eng. Sci., 20, 847-858 (1980) volume honoring Prof. B. Maxwell).]...

J. D. Domine and C. G. Gogos, Compuiter Simulations of Injection Molding of a Reactive Linear Condensation Polymer, SPE ANTEC Tech. Papers, 22, (1976). 

Phenolic and other formaldehyde condensation polymers are also important reactive adhesives. Powdered phenolic resin is mixed with abrasive grains and the mixture is compression molded to form grinding wheels. A B-stage phenolic (Chapter XX) in a solvent is used to impregnate tissue paper. The solvent is evaporated, and the dry sheets are placed between layers of wood in a heated press, where the resin first melts and then cures, bonding the wood to form plywood. Similarly, sheets of paper impregnated with a B-stage melamine-formaldehyde resin are laminated and cured to form the familiar Formica counter tops. 

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