Cellular Plastics Panels Cut Weight
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FRAMELESS construction of commercial-vehicle bodywork has been brought a step nearer by the plastics development work of Locomutors, Ltd., Birmingham, who are now producing polyurethane sandwich panels for doors.
The polyurethane cellular structure is 1-in, thick and is encased by a skin of 1-oz. matt glass-fibre. A variety of sections is being produced and the user is offered a choice of materials with different " sponginess " characteristics. The panels depend upon bulk to provide rigidity, but afford a substantial saving in weight. Colour impregnation can be applied in the normal way. Polyurethane is available in sections and in liquid form, the liquid being employed for moulding curved sections. Brackets can readily be fitted to a panel with through bolts, the tightening of which slightly compresses the material. An outstanding advantage of the material is its good insulation properties.
Its K factor compares with that of polystyrene
Clifford Welch, editor of our associated journal, Plastics, writes: Sandwich construction has been brought much Closer to reality by the introduction of polyurethane core materials, which are capable of close control during the foaming process. In situ foaming between sheets of curved or flat
polyester glass laminate gives extremely high bondstrength .between the spins of the polyurethane core.
For integral construction of vehicles when insulation iS required, these materials may play a leading part. The only possible drawback in the matter of strength may be that unit Construction would he necessary. Where sandwich components were joined together, bond strength at these junctions might not reach the level achieved by in situ foaming. Probably design could take charge of this point. A promising .development is the .work carried out by Bakelite, Ltd., who are using phenolic foam in place of polyurethane. Phenolic resins would be substantially cheaper, with a high insulation value and a comparable strength value to polyurethane. Finally, the ability to carry out in situ foaming in complex curvatures may offer economic advantages.