Following the first part of the article, which discussed the various forms of multi-component molding available for thermoset resins, the second part focuses on the use of this method for thermoplastics. While the former segment covered some large-scale molding technologies, it is clear that the use of thermoplastics has given rise to an even larger tonnage, although the in mold decoration (IMD) process has been used for several years for thermosets and only began to seriously take off in the late seventies and early eighties in case of thermoplastics. In-mold labelling (IML), another version of IMD, was brought about by the high demand for injection molded and thermoformed food containers. For years butter, margarine and other high-fat foods had been packed in aluminium foil or greaseproof paper. The foil or paper was pre-printed, which presented a low cost method of both brand identification and protection of the contents. This was clearly not good enough since the percentage of goods lost by damage, pest attack and shear misuse, eliminated any cost saving realised by this simple packaging method. A more rigid and protective package medium was sought, which at first gave rise to the multilayer thermoformed briquette, developed by Unilever in Belgium. Several alternatives were sought, including thermoformed ABS, but the development of suitable grades of PP solved both the injection molding and thermoforming problems. At first the labelling was applied post-molding by various printing processes. This, while being cost effective process, was still not good enough. It took a Scandinavian company to come up with the final solution, which is currently the practice employed today.
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