Polyurethane reaction molding

Due to the exothermic nature of the reaction and the phase separation which occurs, temperature and conversion (and MWD and sequence distribution) can only be assigned local, not global, values in polyurethane reaction molding. 

Siloxane containing polyester, poly(alkylene oxide) and polystyrene type copolymers have been used to improve the heat resistance, lubricity and flow properties of epoxy resin powder coatings 43). Thermally stable polyester-polysiloxane segmented copolymers have been shown to improve the flow, antifriction properties and scratch resistance of acrylic based auto repair lacquers 408). Organohydroxy-terminated siloxanes are also effective internal mold release agents in polyurethane reaction injection molding processes 409). 

RIM Abbreviation for reaction injection molding. The RIM process involves the rapid metering and mixing of polyurethane reaction ingredients, followed by their injection into a mold. It allows the rapid production of molded polyurethane components. 

Fig. 13.46 Temperature distribution in a reacting polyurethane slab isothermal-wall simulations. Dotted line denotes the adiabatic temperature rise and x s indicate gel points, k = 1, n — 1, AT — 0.423, and B = 18.7, 4>gel = 0.707. [Reprinted by permission from E. Broyer and C. W. Macosko, Heat Transfer and Curing in Polymer Reaction Molding, AICHE J. 22, 268 (1976).]...

Reaction molding method has given composite impact and wear resistant reinforced gradient polymeric materials, based on polyisocyanurates (PIC) and polyurethanes (PU). 

Lee, L.J. Polyurethane reaction injection molding Process, materials, and properties. Rubber Chem. Technol. 1980, 53, 542. 

Low density reinforced reaction molded polyurethane (LD-RRIM) is claimed to simplify production of interior automobile components. 

What is known as the RIM process (reaction injection molding) is a variant of injection molding. In RIM, injection molding and cross-linking polycondensation occur simultaneously. The process is exclusively used to produce polyurethane injection moldings. 

Bayer Bayflex elastomeric polyurethane reaction injection molding (RIM) is a two-component diphenylmethane diisocyanate- (MDI)-based liquid system produced in unreinforced, glass-reinforced, and mineral-Zmicrosphere-reinforced grades. They possess a wide stiff-... 

NIR transmittance spectroscopy was used to monitor polyurethane reaction extent in situ during a reaction injection molding (RIM) process. Good agreement was observed between multivariate (PGA) analysis, univariate (Beer-Lambert) analysis, and kinetic predictions. It was demonstrated that PGA methods with carefully chosen spectral ranges could provide estimation of the reaction extent without time-consuming calibration [83]. 

In polyurethane reaction injection molding technology, self-releasing systems are under investigation. Composition of reactive components (polyols and isocyanates) is used to develop systems which do not require release agents. 

Bruins PF (ed) (1976). Unsaturated Polyester Technology, Gordon Breach Science, New York. Castro, J (1980). Mold Filling and Curing Studies for the Polyurethane Reaction Injection Molding Process, Doctoral Dissertation, University of Minnesota, Minneapolis, Minnesota. Castro JM, Macosko CW (1982). AIChE J. 28 250. 

The sandwich-type stmcture of polyurethanes with a smooth integral skin produced by the reaction injection molding process provides a high degree of stiffness as weU as exceUent thermal and acoustical properties necessary for its use in housing and load-bearing stmctural components for the automotive, business machine, electrical, furniture, and materials-handling industry. 

Another type of polyol often used in the manufacture of flexible polyurethane foams contains a dispersed soHd phase of organic chemical particles (234—236). The continuous phase is one of the polyols described above for either slab or molded foam as required. The dispersed phase reacts in the polyol using an addition reaction with styrene and acrylonitrile monomers in one type or a coupling reaction with an amine such as hydrazine and isocyanate in another. The soHds content ranges from about 21% with either system to nearly 40% in the styrene—acrylonitrile system. The dispersed soHds confer increased load bearing and in the case of flexible molded foams also act as a ceU opener. 

The major uses of aniline are in the manufacture of polymers, mbber, agricultural chemicals, dyes and pigments, pharmaceuticals, and photographic chemicals. Approximately 67% of the wodd production of aniline is used in the manufacture of rigid polyurethanes and reaction-injection-molded (RIM) parts for the constmction, automotive, and durable goods industries. 

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