Polypropylene put to commercial use By P. Abbenheim THERE is considerable interest in the recent announcement that Courtaulds has started production of a polypropylene fibre. This is a completely new form of ' synthetic fibre and an important future is predicted for it in all sections of the textile industry, particularly for industrial use' where its interesting chemical properties will be of considerable value. It is chemically inert, for example, and therefore ideal for making protective clothing and filtration media. Although propylene has long been known to chemists it was of no commercial significance until Professor Giulio Natta of the' Institute of Industrial Chemistry, Milan Polytechnic, discovered a method of polymerising it. By his process, which uses some novel catalysts, the polymer is produced so that the molecular arrangement is symmetrical instead of random. This enables chain polymers to be made that have plastic forming properties, whereas previously they were merely viscous liquids. These are known as isotactic polymers and they are of particular interest to industry because they confer on materials very important physical properties. Isotactic polypropylene is made from the waste material of oil cracking plants and is therefore cheap. It can be used for plastic mouldings or, if extruded, fibres. It has long been the dream of fibre producers to make a fibre with the properties of a fully synthetic, but at a price midway between the regenerated, cellulosics (rayon) at about 2s a pound and the fully synthetics at about 10s a pound. In Italy, Montecatinl Is now building a A simplified arrangement showing the make-up of an ordinary chain polymer (above) and the ordered arrangement of molecules in the isotactic polymer ( below) By courtesy of General Electric, United States fibre plant to make a polypropylene fibre which it says will sell at about 800 lire per kilogram (about 4s 2d a pound). This is clearly an extremely attractive price to textile manufacturers. In the United States a polypropylene fibre has just been put into production while in Britain an agreement has been concluded between Shell and I.C.I, to produce polypropylene. Chemically this new material is related to polythene but it is lighter and has a higher melting point, two big advantages as far as textiles are concerned. It does, however, suffer from ultra-violet degradation .and strong sunlight can cause it to lose its strength quickly. This is something to which technicians will, no doubt, give a high priority in their research. The compact symmetrical chemical structure of polypropylene means that It is completely non-absorbent. This is an advantage and also a disadvantage. It means, for example, that it cannot be dyed and the only way. at present, of colouring it. is to incorporate the colour in the polymer before it is made into fibre. The advent of polypropylene fibre Is an important event in the history of man-made fibres. Where it fits in the scale of fibre prices can be seen from the following list of staple prices for the main British man-made fibres : (per lb.) viscose rayon. Is lOJd; acetate, 3s ; polypropylene (L.800kg.), 4s 2d ; Tricel, 4s 6d ; nylon, 9s 9d ; Teryiene, 10s.. Although Courtaulds has not released technical details of its new fibre, Montecatini reports that its polypropylene has a specific gravity of 0.91, compared with 1.32 for wool and 1.5 for cotton, which means that' when converted Into fabrics It should give bulkier and lighter materials.