Moulding with decorative films

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). 

In all cases the film is an external layer on the moulding, which means that the melt has to be injected through a core located in the fixed half of the mould. 

Locating the gating at the side most often causes deformation of the film, with shifting and deformation of the overprinting of the design. Only single- or multiple-point frontal melt feed ensures that the right conditions are provided for proper flow in the cavity. 

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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). 

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. 

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. 

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

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... 

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