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15. We may usefully refer to an extract from the chapter on polyesters in Volume 11 of Encyclopedia of Polymer Science and Technology at page 35 under the heading "Commercial Development of Polyethylene Terephthalate)". It is stated in that chapter that polyethylene terephthalate) is a fibre-making polymer discovered in England in 1941 and it was recognised at an early stage to be a material of unusual interest and developmental investigations on the polymer and its fibres were undertaken first by British Government research laboratories and later by Imperial Chemical Industries Ltd., who acquired rights to the basic Calico Printers Association patent (46) for all countries except the United States, where it was sold to E.I. du Pont de Nemours and Co. It refers to the several trade marks of polyethylene terephthalate fibres in different countries. It is also stated in that chapter that concurrently with its role as a fibrous material, polyethylene terephthalate has come into use as a source of high strength biaxially drawn films (e.g. Melinex in the United Kingdom, Mylar in the United states) which are noted for their high transparency and dimensional stability. These are used extensively as electrical insulators; for photographic and drawing-office use; as bases for magnetic recording tapes and typewriter ribbons; in decorative laminates and panelling; and as a vacuum-formable crating and packaging material. A polyester is a high polymer and includes a variety of materials having properties ranging from hard and brittle to soft and elastic. Addition of such modifying agents as fillers, colorants, etc., yields an almost infinite number of products collectively called plastics High polymers are the primary constituents of synthetic fibres, coating materials (paints and varnishes), adhesives, sealants, etc. (See 'polymer, high in Condensed Chemical Dictionary). A polymer has been described as a compound formed by the reaction of simple molecules having functional groups that permit their combination to proceed to high molecular weights under suitable conditions and polymers may be formed by polymerization (addition polymer) or polycondensation (condensation polymers). Condensation is a chemical reaction in which two or more molecules combine, with the separation of water or some other simple substance. If a polymer is formed, the process is called polycondensation. (See Condensed Chemical Dictionary).

28. At this stage we may refer to the nature of the market which the polyester products have. In Encyclopedia of Polymer Science and Technology, Volume 11, published by Interscience Publishers, it is stated as follows :-

"Characterization -
Because of the multiplicity of types, grades, and uses of polyester products there are no uniformly accepted specification and testing standards and the materials are mostly sold on the basis of suitability for particular end uses determined, as required, from such properties as the melting and/or brittle temperature, viscosity, colour, haze, moisture content, storage life, unsaturation, and end-group content."
"Polyester Resins.
In the broad sense of the term, polyester resins include many types of resinuous condensation products and collectively represent a broad and expanding field in the plastics industry... As indicated in another section, alkyd resins are basically polyesters. Saturated liner polyester resins can be film or fibre-forming material, for example, polyethylene terephthalate."

38. Reference is made to Plastic Chemistry And Technology by W.E. Driver, in which under the heading "Thermoplastic Polyesters" it is stated that Glycols are reached with terephthalic acid or dimethyl terephthalate to form a linear polymer and this type of polymer is sold as fibre and film under several trade names. A quotation from Modern Plastics Encyclopedia at page 544 was produced to indicate that mylar (trade mark of E.I. du Pont do Nemours & Co. Inc.) is prepared from polymer formed by the condensation reaction between ethylene glycol and terephthalic acid.

39. It was also contended on behalf of the respondents that the use of a delustrant, namely, titanium dioxide does not affect that usability of the polyester for making films and that there is no change in the chemical character of the polyester by the addition of the delustrant and the polyester resulting from the process of polycondensation, during which process the delustrant is added, is still a resin. In support of the contention that by the addition of titanium dioxide, which is admittedly a delustrant, no chemical reaction takes place, reference was made to a passage from The Encyclopedia of Basic materials for Plastics by Simonds and Church at page 473 where in reference to titanium dioxide pigment, the following is stated :-