Abstract
An account is given of an investigation carried out at the Chemical Research Laboratory, Teddington, on the fibreโforming polyester, polyethylene terephthalate which was recently announced by the calico Printers' Association and Imperial chemical Industries under the registered name of โTerylene.โ The major part of the investigation was carried out under extraโmural contract with the Ministry of supply, and in collaboration with the Calico Printers' Association, but the latter part was carried out independently. the polyester is obtained from ethylene glycol and methyl terephthalate by ester interchange, and its preparation is covered by B.P. 578079 (Whinfield and Dickson).
To prepare the necessary large of terephthalic acid, pโcymene was oxidized with nitric acid and the product further oxidized with potassium permanganate to terephthalic acid. This was esterified, and purified by vacuum distilation and subsequent crystallization. The condensation of glycol and methyl terephthalate was carried out both in glass and in metal apparatus: the form of apparatus employed and the conditions of preparation are fully described . Attempts to produce satisfactory filaments by extruding the melt under a high pressure of nitrogen were unsuccesful, partly because the solid polyester suffers degradation when melted and so yields week filaments, and partly because the filaments contain bubbles due to liberation of dissolved nitrogen. Filaments were prepared by extruding the polyester from a glass apparatus immediately after preparation. The filament was coldโdrawn into fibre by passage through two pairs of mechanically driven rolls geared in the ratio of 1:4. The maximum strength of the fibre was 5 g. per denier, and the extension at break was about 12%. The waterโabsorption of the fibre was very low, but the dielectric properties were not outstanding. Photomicrographs of filaments and fibres illustrate certain faults which were encountered, and attention is drawn to the fact that although the filament is transparent the fibre is subtantially opaque. The cause of this opacity is discussed.
It is concluded that the maximum strength of polyethylene terephthalate fibre was not reacdhed. The observed properties of the fibre and the fact that it can be produced in metal apparatus suggested that industrial development was desirable. This development was undertaken by Imperial Chemical Industries.