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The Cold Calamity
Design problems that result in disasters can be caused by anything from a miscalculation of service conditions to the selection of the wrong material or processing technique. This one came from a combination of misreading the physical property data on polypropylene and forgetting that part of the exposure environment for the product is its transportation to the destination for use.
Portable TV sets have been housed in plastics cabinets for many years. The cabinets are made with a front section that contains the set and a back cover that houses the back end of the cathode-ray picture tube.
When polypropylene first became available, it was evaluated by a major home-electronics producer for the back cover application because of its better electrical insulating qualities, lower weight, better resistance to cold flow and better manufacturing cost as compared with the impact polystyrene and ABS then in use.
Since all of the indications looked good, and there was a push for lower cost and good performance in a highly competitive market environment, the decision was made to convert the entire production of the sets for that year without the normal one-year trial.
The decision worked out well. Costs were down and the PP component passed all of the tests. Since the portable TV is a Christmas item, the sets were made in quantity in advance and shipped in November and early December. The failure reports started coming in shortly after shipping, and there were so many (Continued on page 5)
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