In-mould coating

Polymeric vinylidene chloride generally produced by free radical polymerization of CH2 = CCl2. Homopolymers and copolymers are used. A thermoplastic used in moulding, coatings and fibres. The polymers have high thermal stability and low permeability to gases, and are self extinguishing. 

Glossy polymers can be obtained by polishing, post-moulding into perfectly polished moulds, lay out of films, IMD, FIM (film insert moulding), IMC (in mould coating), painting... 

Plasticised suspension PVC is first melt compounded and then extrusion coated onto copper wire to provide electrical insulation. It can be calendered between parallel rolls to produce flexible sheeting for flooring. Emulsion PVC can be converted into a plastisol by mixing it with a high proportion (50-70%) of a plasticiser. The plastisol, containing swollen 1 xm particles suspended in the plasticiser, is a liquid at room temperature with a medium viscosity of 20-50 Nsm . It can be rotationally cast in moulds, coated onto wallpaper or cloth, or used to dip-coat metal products. A subsequent heating to between 150 and 175 °C causes the rest of the plasticiser to be absorbed in the PVC and the particles to fuse into a homogeneous solid. 

J Humberstone, New In-mould coatings for RTM , BPF Composites 96 Conference Papers, British Plastics Federation Sept 1996. 

In-mould coating should be mentioned here for completeness. This technique is widely used for integral skin foam components in PUR, principally in the passenger compartment. It is also used to prime SMC parts, as an aid to producing a Class A finish on the topcoat. The RTM methacrylic resin panels of the Alfa Romeo SZ were in-mould coated to a Class A finish. As this was a specialist vehicle and no other painted panels were involved, the usual problems of reduced production rate and poor colour matching did not apply. 

Company manufactures under licence the full range of Cook Composites and Polymers, in-mould coatings. 

A series of hard, acrylic urethane, in-mould coatings which can also be employed as a post-mould finish, of. excellent weatherability. 

A series of flexible aliphatic urethane, in-mould coatings of outstanding colour retention. 

A proprietary, new generation, preaccelerated thixotropic in-mould coating for brush and spray application, setting new standards of colour stability, gloss, weather and water resistance. Available in a limited range of colours. Approved by Lloyd s Registry. 

Elastomeric polyurethane RIM, two-component MDI-based liquid systems available unfilled, glass-filled or mineral/microsphere filled offering large part mouldability, superior impact strength and excellent surface quality and in-mould coating, for agriculture, construction, automotive and special transportation application. 

Surface defects, resulting from air traps blistering in post-moulding operations. Low profile additives and in-mould coating techniques have provided only limited relief from the defects. Usually costly and time consuming post-moulding filling has to be carried out before a cured SMC component can be painted. 

Figure 11.7 Range of in-mould coated, semi-rigid, self-skinned PU foam mouldings. By permission of Marley Foam, Sheller Clifford and Bridgtown Industries...

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