Two-component injection moulding

Interface Reactive Two-Component Injection Moulding (Core-Back Process).183... 

Fig. 11 Two-component injection moulding (foimation of test specimen with two boundary layers/interfaces)...

The first results of an interface reactive injection moulding by two-component injection moulding (Fig. 11) are listed in Table 11. 

Fig. 12 Interface reactive two-component injection moulding - bond strength in dependence on the type of diisocyanate and TPU elastomer. Bond strength between PA-6/TPU. PA-6 Ultramid B3S TPU Elastollan 1185A, Elastolian B 85A, Eiastollan C 85A, Elastollan C 60D. Modifiers diisocyanates MDI, IPDI, IPDI-Uretdion, PBDI, Oligomer-TDI-DI. Addition of 1 up to 5 wt% ...

Fig. 13 Interface reactive two-component injection moulding - image of fractured specimen after tensile test, polyamide bulk material on the TPU fracture surface (right - fracture with coloured TPU part for differentiation)...

Table 12 Interface reactive two-component injection moulding — bond strength betweai different polyamide materials [32]...

Interface Reactive Sandwich Moulding as a Special Two-Component Injection Moulding System... 

This list of applications gives just a brief idea of items currently produced using two-component injection moulding techniqnes or insert parts. 

LR in Two-component Injection Moulding Technology (Two Colour Mould)... 

In the two-component injection moulding processes the slower of the two steps is cycle determining. The thermal properties of both silicone and plastic materials require compromise with respect to temperature in both cavities which deviates from the ideal conditions for simple injection moulding. 

In two-component injection moulding for the production of thermoplastic/silicone composites, the moulding temperature for the thermoplastic should be as high as possible for two reasons. Firstly, when the thermoplastic solidifies, residual stresses are frozen in. This can lead to... 

Materials suitable for two-component injection moulding are both normal and self-adhesive LR. 

As an example consider silicone keypads. The first silicone components are conductive pills. They can be incorporated using inserted part technology as well as in two-component injection moulding, the latter preferably using LR. 

In medical technology, there is an increasing trend for smart products. These are made possible by modem processes such as laser marking, two-component injection moulding and MID technology. Current examples include functional dmg delivery systems like pens for active ingredient injection and needleless syringes. 

As mentioned earlier, the insert parts can be produced by any apparatus. This can be extmsion with subsequent cutting, injection moulding, two or multiple colour (also two or multiple component) injection moulding, press moulding, punched and bent metal sheets, cast iron, sintered metal, ceramics in any shape, cut glass, etc., or moulded or extruded silicone rubber (as in catheters and insulators). 

Most tests will be made on standard test pieces which may be pieces cut from a component or a sheet, or they may have been moulded separately from the same material. Where test pieces or sheet are produced for the trials it is important that they are produced in as near as possible the same way as the product and that the processing conditions are recorded. Different results can be expected from compression and injection moulding or from extrusion (where a choice is possible). Directional properties can result from the conditions of flowing and cooling in a mould. For example, in a study at ERA, the creep strain of unfilled HDPE, either individually moulded or cut from square plaques, varies by up to a factor of two depending on the orientation of flow [40]. This difference becomes even more marked with short fibre reinforcement. 

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

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],... 

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. 

The two components are kept in temperature-controlled tanks, with pumped re-circulation when injection is not taking place. For the polyurethane system, one tank contains an isocyanate (usually MDI) and the other a mixture of polyol, chain extenders, catalyst and mould release (and possibly blowing agent or reinforcing additives). An amine catalyst accelerates the initiation of the polymerisation, while an organotin catalyst... 

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