Moulding processes reaction injection

Figure 6.5 Flow scheme of polydicyclopentadiene production via ring-opening metathesis polymerisation in the reaction injection moulding process...

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 ... 

Kinetic and mechanistic studiesoftheimidizationreactionhave been made and the effects of amine activators, catalysts, and palladium " have all been studied. Imide plastics have also been produced by the reaction of diamine-esters of poly(dicarboxylic acid) on filler surfaces in a quasi reaction-injection moulding process. ... 

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

An important development of polymerisation casting is that of reaction injection moulding. Developed primarily for polyurethanes (and discussed further in Chapter 27), the process has also found some use with polyamides and with epoxide resins. 

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. 

Cast nylon is used for prototypes and small production runs processed by casting, roto-moulding and reaction injection moulding (RIM), possibly with structural reinforcements (SRIM) such as glass mat or fabric. 

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

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],... 

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. 

PHD polyols are successfully used for high resilience flexible PU foams (made by the cold cure process), for continuous slabstock flexible PU foams and for elastomers obtained especially by reaction injection moulding (RIM) technology. 

Injection moulding can be applied to two-component thermosets in a process known as Reaction Injection Moulding. The two liquid components are mixed and then injected into a closed mould. In the case of epoxies and polyurethanes, heat is produced on mixing due to the exothermic reaction between the two components (polyol and isocyanates in the case of polyurethanes), so no external source of heat is required. 

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