chapter  4
22 Pages

New Industries—Synthetic Rubber and Plastics

In the first place, it must be noted that there is no such thing as " synthetic rubber " in the literal sensethe precise chemical structure of natural rubber is not known, and no substance has been synthesised which is identical with it in physical properties. It is known, however, that the peculiar properties of rubber, especially its elasticity and resilience when suitably vulcanised, are due to the fact that its molecules consist of immensely long chains, the individual links of which are fairly simple. It has been known for over eighty years that one of the relatively simple substances into which rubber can be broken down-isoprene, the precise structure of which was determined some twenty years later-tends to become viscous on standing, and it was subsequently found possible to reconvert it into an elastic, rubber-like substance. In the first decade of the present century, it was discovered that other substances, cnemically related to isoprene, may likewise be converted into rubber-like solids, and in 1910 the Russian chemist Lebedev showed this to be possible with butadiene-the compound of which isoprene is a simple derivative, and from which a great deal of the subsequent development has come. In the same year the English chemists Matthews and Strange showed that

the polymerisation of butadiene (i.e., the joining together of its molecules into very large ones which constitute the elastic solid) is strongly promoted by sodium-hence the

Process which was started commercially in Germany and .ussia ten years ago, and from which the German name Buna comes (i.e., from the initial letters of fa/tadiene and wfltrium).