PHOTOGLAZE, PERSPEX, NEW DOMESTIC BOONS

Press, Volume LXXXII, Issue 24911, 26 June 1946, Page 6

PHOTOGLAZE, PERSPEX, NEW DOMESTIC BOONS

FROM WAR TO PEACE

hv Dr W F COXON. formerly principal Scientific Officer in [BroadCast i .by g Dr. .^r production, in the 8.8. C. s Pacific Sen-ice.]

i Glamorised accounts of the possibilities of plastics confront us daily in the press. We read of plastics for furniture, motor-cars, shoes, stockings, and jewellery—and they are only a few The more sensational writers even refer to a plaetics age. This misguided enthusiasm has done the industry some harm already by its exaggerated claims. Nevertheless, our large war-time requirements have undoubtedly stimulated our plastics development, and now this war-acquired knowledge is available in more pappy circumstances. But before I describe the peacetime uses that I have seen already in our factories, I ought to say what plastics really are. Or, first of all. what th '?hey rC are *not a substitute for anything—but they very often replace a natural material in industry because they can do the job better. They are a synthetic or man-made raw material—a kind of resin—made from chemicals, and, as a rule, they get their names according to the particular chemicals used in their manufacture. I think I ought to say here that when you hear of plastics being made from coal, what is really meant is that the by-products from coal distillation in the manufacture of gas and coke are essential ingredients in the chemistry of plastics. The Three Main Groups of Plastics Plastics are not all alike—and they ere varied in their uses according to their chemical nature and their different behaviour. There are three main groups—the simplest ones are called thermoplastics, and they only need to be heated to give the final shape we want; but, of course, this means that articles made from them are liable to soften if they get hot. They are well known to you as celluloid and perspex: and others are cellulose acetate and chloride—or PVC, as it is called- This group is all made in a similar way by the polymerisation, or joining together, of different chemicals. Cellulose acetate is made up by treating wood pulp or cotton—which, of course, are different forms of cellulose —with acetic acid. However, perspex is a trade name, gone into common usage, for polymethylmethacrylate—and it is somewhat easier to say. These thermoplastics are easily made into any shape, but tjiey are easily, scratched and are useless for any article which has to withstand heat. But they are very useful for such things as photograph frames, cigarette boxes, lamp stands, and dress ornaments—and, of coarse, combs. The next class is more complicated. They are made from materials which harden or set when heated, so the name thermogetting plastics is given to themPerhaps their best-known application is in making electric switch covers. The manufacture of the plastic is rather interesting. The two chemicals, phenol and formaldehyde, are heated together. The chemical action is stopped at a point which gives a soft material rather like treacle. This is then mixed with sawdust and coloured dyes to give a powdery substance called moulding powder. Meanwhile, a steel mould or shape, like that of our electric switch cpver, is made in two halves so that they can be pressed together leaving a space between them having the same shape as the cover. The moulding powder is poured into the lower part of the mould, and compressed by hydraulic pressure under a heavy press, whilst at the same time the temperature of the mould is raised by steam. The chemical reaction, which had been purposely stopped half-way, is now completed by the heat and pressure, so that we are left with a hard shape exactly like the hollow space in the mould.

When this is opened into its two halves, out comes our electric switch cover almost ready for use. Materials prepared this way—thermosetting plastics—are among the best-kpown plastics, and are particularly useful where the article has to stand up to heat—as, for example, in the handle of an electric iron. Aircraft to Kitchen

The other plastic materials which have really revolutionised the industry are called laminated plastics. They were largely used ip the construction of the record-breaking Mosquito aircraft. The lessons learnt here in the war years are now bringing us kitchen cabinets, tables, and bathroom fittings, superior to those previously obtainable at such low prices. For these plastics, we take layers of wood cotton, or paper, and eoat them with the thermosetting plastic resin I have just been talking about This is the resin in which the chemical reaction has been allowed to go only part way. These resin-treated materials are then pressed together under a heated press at many tons pressure. The resin then hardens and joins these thin layers of wood, cotton, or paper together very firmly. These plastic-treated layers of materials are called laminated plastic*. Instead of pressing them into sheets, we can, of course, press them over a former having the shape of the fuselage of aircraft or, as now, into cases sorf SeWlnB mach^nes and things of that Now for the way we can expect these materials to help us to live more comfortably and hygienically in the years to come. First, plastics in the home and what l S a & ° W’i 1 saw some kitchen cabinets and kitchen cupboards the other day being made in a well-known factory from laminated wood and paper plastics. They had five drawers

. at either end with two central doom i The drawers moved as freely as could ■ be, because they do not warp livZ wood ones. J The aluminium shelves were coatsd . with a plastic skin, and the knob, the drawers and doors were recessS to avoid catching pockets or aprons They were cream m colour, and ’ plastic skin does not scratch or absorb spilt liquids like wood or rust and ' rattle like metal ones. ; Then there were some thermosettiu. 1 plastic kitchen bowls and colandeS in the gayest colours—they are liahi in weight, and the colours will mattk any kitchen scheme. They do not bresir or chip if you drop them, and their' : design will let you stack them i R the ■■ kitchen quite conveniently. At another factory, I saw some plastic kitchen spoons and salad servers of a similar I material—they do not stain with vine. ■ gar, and they do not break like glass ones when you are washing up. The Nursery In the kitchen, where cleanllnese is most important, wood table tops, roil-' i ing nins, baking boards, and brehk boards are a nuisance. The wood i, porous, and no matter how much you wash them, food and dirt are absorbed into the wood. Plastics, on the other hand, are hard and non-porous, so thet you keep away dirt and stale food by just a rub down. Plastics in the kitchen are both hygienic and labour saving. And then, of course, there is th, nursery. Take the kiddies’ high chair, for example, where even the most well-behaved baby delights in taking the food off his plate, or his milk out of the cup, and mixing them together on his tray. Of course, he has no use for the plate and cup—these go op the floor. Well, at another factory they had taken care of this—the high chair tray was of laminated plastic and was, therefore, cleaned with a rub: and the plates and mugs were of plastic which do not mind oeing bounced on the floor, and the mugs even had little finger-grip handles. Here, in Britain, when we were building motor torpedo boats and motor gun boats in large numbers to keep away Hitler’s U-boats, it used to take six days for the paint on the ship's bottom to dry. A new plastic paint called photoglaze was discovers! and reduced the drying time to one day. Of course, if this paint is good enough to stand up to sea water, it is ideal in the home—and wall boards with this coating of photoglaze are excellent for kitchen and bathroom panelling. Cheap, and Capable of Mass production Plastics are cheap to make and lend themselves to mass production. They are also being made now for prefabricated and permanent buildings, and, like most of our other good things, large quantities are for export Talk, ing of wall panels, I saw some prefabricated wail panels of aluminium and laminated plastic with a spactal interlocking system: two girls were Bbe to erect a nine-foot partition wall in two minute?. Perspex is a fascinating thermoglastie— it ’is transparent, like glass, ut does not splinter, and can now be coloured to any shade. In Britain we developed this material to a considerable extent during the war. Then, we used it in aircraft for the bombaimer’s cabin, the navigator’s astral dome, and the airgunner’s gun turret And now I would like to say a word or so about the plastics that the housewife might coma across when she is put shopping or reading some fanri, ful advertisement in the newspaper. Plastics, like everything else, have their snags and limitations. For example, the familiar -bakelite electric light fittings are made of thermosetting plastic. If these are made from a cheap-grade materigl' they will tend to be brittle and break when they are knocked. Since they cannot be repaired easily, they are dear in the end. as well as beiM dangerous. So, when you are buying fittings or articles which are liable Jo be knocked hard, do not go for the cheapest product, because specially strengthened ones are made. Above all, do not buy an article just because it is advertised as plastic. You want an electric iron, for example, to be safe, reliable, and with.a thermostatic cut-out to -avoid overheating. Those are the things to look for in an -iron—and beware when the salesman shies away , from those essentials and bod” 16 t 0 ' tS 10ve!y pl<lrtio handle Most fcnds of plastics require expensive hydraulic presses, and shaped steel moulds made by skilled craftsmen. It is therefore pot worth while making articles ip plasties unless quantities of hundreds of thousands are required. By making such large numbers, the price has been lowered—and, perhaps, had it not been for pU«. tics, you could not have afforded «a many useful and attractive extra things for your home. Plasties are mainly utilitarian. They do not have the varying quaiity of natural materials, sjcfi a? the natural beauty of,- say, a polished lna le t Yu hav « to 80 to nature-" and to the craftsman. But plastics have a beauty of their own, and designers working in this material to.day are making the meat of it. They are designing articles with smooth, clean thTi>e a st n u'se‘ , of V cVou’r they *" maWß< toJZ articles were made Iram wood or other ron r 1 "thterials—they are making full use of the beauty of plastics to us v rl^te r and more hygienic kitchens, lighter and more colourful furnishmgs. and attractive, cheap jewellery and fancy goods.