REACTION INJECTION MOULD

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. 

Reaction injection moulding techniques, developed primarily for polyurethanes (see Chapter 27), have also been adapted for nylon 6 in what must be considered as a variation of the polymerisation casting technique. 

Not only are these reactions of importance in the development of the cross-linked polyurethane networks which are involved in the manufacture of most polyurethane products but many are now also being used to produce modified isocycuiates. For example, modified TDI types containing allophanate, urethane and urea groups are now being used in flexible foam manufacture. For flexible integral foams and for reaction injection moulding, modified MDIs and carbodi-imide MDI modifications cU"e employed. 

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. 

FRISCH, K. c.. Recent Developments in Urethane Elastomers and Reaction Injection Moulded (RIM) Elastomers, Rubber Chem. Technol., 53, 126 (1980)... 

The beneficial effects are demonstrated of heterogeneous secondary pyrolysis reactions on the liquid products of PU pyrolysis. Pyrolysis volatiles are passed through a packed bed of carbonaceous solids that promote the secondary reactions. Activated carbon and reaction injection moulded PU (RIM) char were found to be suitable bed materials. The long-term object was to develop marketable solid products by pyrolysis of wastes, so obtaining high char yields. In addition to affecting the liquid products, RIM char also increased the total char... 

The mixing can be done by hand, or in low pressure mixer/dispensers, and in reaction injection moulding (RIM) machines. In the latter operation the de-gassing operation is not required. 

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. 

Reaction injection moulding (RIM), commonly used with thermosets, is sometimes used for specific thermoplastics such as Nyrim. Nyrim is supplied in two parts ... 

RRIM - reinforced reaction injection moulding - the resin is reinforced with short fibres... 

SRIM or SRRIM - structural (reinforced) reaction injection moulding - mats or fabrics are placed in the mould before injection of the resin, possibly reinforced with short glass fibres. 

Note Reaction injection moulding commonly uses two-component precursors that produce polymer networks after mixing. 

Reaction injection moulding within which glass fibres are included to increase the strength of the moulding. 

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

Kresta JE (ed.), Reaction Injection Moulding and Fast Polymerization Reactions, Plenum, New York, 1982. 

Macosko CW, RIM Fundamentals of Reaction Injection Moulding, Hanser, Munich, 1989. 

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],... 

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