Reaction Injection Molding RIM

Two or more liquids are mixed in a resin pot and fed at low pressure into a closed mold, where they react. This technique can be used to feed catalyzed resin into a pultrusion die. The process can be adapted to reinforced reaction injection molding (RRIM) by introducing milled or chopped fiber. 

This technique, termed rotational molding (e.g. Engel Process), can be used with thermoplastic materials such as polyethylene, polypropylene, nylon, polycarbonate and polyurethane. The powdered plastic is placed in a mold and heated externally in an oven chamber to about 220-400°C, whilst it is rotated around both vertical and horizontal axes. As the powder melts, it adheres to the inner mold surface, building up an even layer over the surface of the mold. The mold, whilst still rotating, is withdrawn from the heated chamber and moved into a cooling chamber and the component removed after solidification [85]. 

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Reaction Injection Molding. RIM uses the anionic polymeri2ation of nylon-6 to carry out polymeri2ation in the mold. A commercial process involves the production of block copolymers of nylon-6 and a polyether by mixing molten caprolactam, catalyst, and polyether prepolymer, and reacting in a mold (27,28). 

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. 

Fig. 19. Typical injection molding and reaction injection molding (RIM) machines (a) injection molding machine for thermoplastics (b) reaction injection molding machine, showing A, the closed position, where reagents circulate, and B, the open position, where reagents are mixed and dispensed to mold.

The largest segment of the CASE family of polyurethanes are elastomers. Cast polyurethane elastomers reached a new dimension when high pressure impingement mixing led to reaction injection molding (RIM). This technology is used widely in the automotive industry, and reinforced versions (RRIM) and stmctural molded parts (SRIM) have been added in more recent years. 

Reaction injection molding (RIM) describes [27-29] the process whereby two liquid reactants are rapidly mixed... 

RCM. See Ring-closing metathesis (RCM) Reaction by-products, removing, 83 Reaction extrusion, 204 Reaction index, 237 Reaction injection molding (RIM), 205 Reaction-in-mold (RIM) nylon, 149 Reaction kinetics, 76, 77 Reaction mechanisms, polyesterification, 66-69... 

Rigid insulation foam, 206 Rigid isocyanurate foams, 226 RIM. See Reaction injection molding (RIM)... 

Conversion of cyclic oligomers to composite structures via Resin Transfer Molding (RTM) and Reaction Injection Molding (RIM) techniques has been demonstrated, and will be the subject of subsequent publications. Glass loadings... 

Reactive oligomers such as epoxy resins, isocyanate-terminated compounds, and urethane-acrylates are extremely useful in the adhesive, coating, reaction injection molding (RIM), sealant and... 

Rigid polyurethane foams account for 80% of MDI use, especially for construction (about half of this use), refrigeration, packaging, and tank and pipe insulation. Other uses are reaction-injection molding (RIM) applications (13%) and cast elastomers (2%). 

Figure 7.85 Schematic diagram of the reaction injection molding (RIM) process.

Resin transfer molding (RTM) is a hybrid of two polymer processing techniques we have already described transfer molding and reaction injection molding (RIM). The key difference is that a reinforcement is incorporated during molding to create a composite. 

The third impregnation method, which is often referred to as injection or reaction-injection molding (RIM) pultrusion, employs a different kind of die. Unimpregnated reinforcement is guided into a narrow opening in the die, which widens into a cavity further downstream where the resin is injected under pressure (see Fig. 11.2). The cavity, which is maintained at a temperature that ensures that the resin does not start crosslinking prematurely,... 

Tungsten-based catalysts with a Lewis base promoter are used in the polymerization of dicyclopentadiene also isolated from the C5 stream-cracker fraction.150,155 The product poly(dicyclopentadiene) or Metton resin has unusual physical and chemical properties. It is processed together with elastomers to increase viscosity of the end product by using reaction injection molding (RIM) technology.155... 

Nylon-6 can also be produced from molten caprolactam using strong bases as catalysts (anionic polymerization) this is used as the basis of monomer casting and reaction injection molding (RIM). Anionic polymerization proceeds much faster than the hydrolytic route but products retain catalysts which may need to be extracted. 

Dicyclopentadiene is also polymerized with tungsten-based catalysts. Because the polymerization reaction produces heavily cross-linked resins, the polymers are manufactured in a reaction injection molding (RIM) process, in which all catalyst components and resin modifiers are slurried in two batches of the monomer, The first batch contains the catalyst (a mixture of WClg and WOCl4), additives, and fillers the second batch contains the co-catalyst (a combination of an alkylaluminum compound and a Lewis base such as ether), antioxidants, and elastomeric fillers. Mixing two liquids in a mold results 111 a rapid polymerization reaction. 

Reaction-Injection Molding and Reactive Casting. Reaction-injection molding (RIM) (22) and reactive casting (23) have been demonstrated on nylon-6, which is polymerized by catalytic ring opening and linear recondensation of S-caprolactam (qv) (24). 

Molding processes include compression molding, resin transfer molding (RTM), injection molding and reaction injection molding (RIM), autoclave molding, and several types of specific processes such as shell molding, which is used in foundries. 

Finally, in the reaction injection-molding (RIM) process, low-viscosity reacting monomers or prepolymers are intimately mixed just before being injected into a hot cavity, where they react further and solidify. The RIM process, then, is a variation of the casting process, where highly reactive liquid systems are injected quickly, rather than being allowed to flow by gravity, into complex shape cavities, where they quickly react and solidify. 

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