Moulding decorative films

Another route to protect polymers from oxygen, light and UV is to encapsulate the part with a continuous film of another, more-resistant polymer to provide a barrier to oxygen. This technology is also used for decoration of plastic parts (in mould decoration or IMD, painting, multilayer sheets for thermoforming. ..). There is no protection against heat. 

For in-mould decoration or in-mould labelling, a decorated film or printed label is precisely located in the empty mould. The molten plastic then adheres onto the film or label during injection. Film is mechanically clamped. The label can be fixed in the mould by electrostatic charge. 

In-mould decoration (IMD) with films reduces finishing operations. If the process and its operating conditions are suitable, the demoulded parts are finished. 

A. C. Y. Wong and K. Z. Liang, Thermal effects on the behaviours of PET films used in the in-mould-decoration process involved in plastics injection molding. Journal of Materials Processing Technology, 63, 510-513 (1997). 

In place of expensive overprinting on products, increasing use is being made of the method of injection onto printed films inserted into the mould, which is called in-mould decoration (IMD). 

Other variations of film decoration are, for example, the rocker moulding for General Motors Chevrolet Trailblazer North Face Edition, a 2-metre-long part thermoformed over injection moulding because of the relatively low volumes (7000 to 8000 vehicles per year) and the short development time required. 

A similar technique may be used to make injection mouldings with elaborate patterns or decorations paper or film may be printed flat with the design required then folded, say, in a box-shape and placed in the mould—where it is held in place electrostatically or by vacuum applied through pins moulding then takes place on or through this substrate. Such an approach has been used to mould boxes for biscuits, showing pictures of the biscuits on the box. It eliminates difficulties associated with printing shaped objects. 

A promising alternative for the production of unpainted body panels is the use of a co-extruded thermoplastic film as a decorative layer which is back-moulded with a thermoplastic material [107]. This technique has received the name paintless film moulding (PFM ) (Figure 16.16). 

In accordance with its extraordinary high toxicity for fungi the active ingredient is mainly used as a fungicide, e.g. for paint film protection, in non-film forming decorative wood stains, in the leather industry for the protection of wet blues, in adhesives and sealants, pulp, paper and cardboard, etc. Surface coatings treated with the fungicide may lose mould resistance when exposed to... 

Dichlofluanide has a broad spectrum of activity (see Table 110) which also covers mercury resistant Penicillium species, but not Trichoderma viride. It is particularly effective against wood-staining fungi (blue stain mould) and therefore one of the most important fungicides in non-film forming decorative wood stains, in wood coatings and primers. 

Finally, mention should be made of the increasing use of mica as a decorative filler in both thermosetting and thermoplastic mouldings. Pearlescent micas in which a thin layer of titcmium dioxide is deposited on the mica surface have been available for many years. These fine flakes are normally silver but a wide range of colours is available. Pearlescent mica is best established in thin film applications. 

Insert moulding with plastics is a two-step process whereby a first preform component is placed into the open mould cavity. Injection then proceeds as with traditional moulding methods with injection of a molten plastic onto the preform. This process is not limited to two material components and the resultant mouldings can be transferred in this way until the required number of layers is achieved. Inserts can be loaded by hand or by the use of robots. Inserts must be accurate in both their dimension and their placement into the over-moulding tool to prevent tool damage and provide accurate registration of one material on another. A means must also exist to hold them in place within the tool. In this way it has similar requirements to that of in mould lamination techniques commonly used to decorate plastics with films or foils, details of which can be found in a specialist Rapra Review Report [4] and will not be covered further here. 

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