The structure and electrical properties of poly(1,4-cyclohexylenedimethylene terephthalate), a new linear thermoplastic polyester

During the past 12 years, only two thermoplastic linear polyesters capable of forming films suitable for electrical insulation have been commercially available. These are poly(ethylene terephthalate) and another polymer in which a considerable portion of the terephthalic acid in the poly(ethylene terephthalate) configuration is replaced with isophthalic acid. As far as electrical uses go, however, poly(ethylene terephthalate) has been used almost exclusively. This paper introduces a new linear polyester, poly(1,4-cyclohexylenedimethylene terephthalate), designated hereafter as T16, which was designed with outstanding chemical and electrical properties. This polymer is formed by reacting terephthalic acid and 1,4-cyclohexanedimethanol. In Figure 1, the repeating units of T16 are compared with those of poly(ethylene terephthalate). It is readily seen that the big structural difference is the presence of a cyclohexane ring between the two methylene groups. This bulky ring and its attendant forces impart a lower density, a higher melting point, and substantially better hydrolytic, chemical, and electrical properties to T16.