Reaction injection moulding polymer processing

The reinforced reaction injection moulding (RRIM) process is a development of RIM in which reinforcing fillers such as glass fibres are incorporated into the polymer. One advantage of such a system is to reduce the coefficient of thermal expansion, and with a 40-50% glass fibre content the coefficient is brought into line with those of metals. 

The metathesis polymerisation of dicyclopentadiene, an inexpensive monomer (commercially available cyclopentadiene dimer produced by a Diels-Alder addition reaction containing ca 95 % endo and ca 5 % exo form), leads to a polymer that may be transformed into a technically useful elastomer [144-146, 179] and thermosetting resin [180,181]. The polymerisation has characteristics that make it readily adaptable to the reaction injection moulding ( rim ) process [182], The main feature of this process comes from the fact that the polymerisation is carried out directly in the mould of the desired final product. The active metathesis catalyst is formed when two separate reactants, a precatalyst (tungsten-based) component and an activator (aluminium-based) component, are combined. Monomer streams containing one respective component are mixed directly just before entering the mould, and the polymerisation into a partly crosslinked material takes place directly in this mould (Figure 6.5) [147,168,183-186],... 

Catalysts are essential components in the liquid injection moulding (LIM) or reaction injection moulding (RIM) processes. Prepolymer systems for solid polyurethane elastomers usually do not require catalysts, and if long-term hydrolytic stability is required in the final polymer their use is undesirable. 

Rigid integral skin structural foams are produced in polyurethane materials by the reaction injection moulding (RIM) process. Components of the polymer are metered via a mixing chamber to give a measured short shot in a tool cavity where the polymerisation and the foaming action, which expands the material to fill the cavity, take place. At the cavity-moulding interface the bubbles formed by the... 

M. E. Edwards, Chemical Reaction Engineering of Polymer Processing Reaction Injection Moulding Inst. Chem. Eng. Symp. Ser. 8(87), 783—796 (1984). 

Note 3 Reaction injection moulding and reinforced reaction injection moulding are types of reactive polymer processing. 

In recent years a new type of thermosetting polymer based on polydicyclopen-tadiene has been developed and marketed. Usually this is amber in colour and it is made by a reaction injection moulding process employing various catalysts ... 

Reaction injection moulding (RIM) is a low-pressure process that allows two reactive streams, A and B say, to meet and react to form a cured polymer in the mould. Figure 6.16 shows the process in a simplified form. 

RRIM is a development of the RIM process (reaction injection moulding). The essential feature of an RIM system is a 2-component liquid resin system which reacts rapidly when the two components mix, to form a fully developed polymer inside the mould. Usually these systems are polyurethanes, although others, especially nylon-based systems, are under development. 

Injection moulding is by far the most frequently applied technique for manufacturing end-products directly from a thermoplastic raw material. In this process articles are formed by injecting the molten polymer into a cooled mould. Also on rubbers and thermosets this method is applied, though at a smaller scale in these cases the mould is heated rather than cooled in order to promote the vulcanisation or curing reaction. 

These materials are shaped by reaction processing, such as screw transfer injection or compression moulding, although glass reinforced polymers (GRP) are frequently moulded using hand lay-up or spray techniques. The injection techniques and compression moulding of cross-linking plastics do not have... 

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