Two series of amorphous copolyesters, PETGN and PETGS, were synthesized by the copolymerization of 2,6-naphthalene dicarboxylic acid (NDA) (0-40%), succinic acid (SA) (0-40%), 1,3/1,4-cyclohexanedimethanol (1,3/1,4-CHDM) (10-50%), ethylene glycol (EG), and terephthalic acid (TPA). The compositions and molecular weights of the copolyesters were determined by 1 H NMR spectroscopy and viscometry, respectively. The thermal behaviors were studied over the entire range of copolymer compositions, using DSC and TGA. The optical characteristics, heat-shrinkable effects and tensile properties of these polymers were also determined. Experimental results indicated that the thermal, optical, tensile, and shrinkage properties of PETGN and PETGS were functions of NDA or SA content. DSC and X-ray analysis demonstrated that both PETGN and PETGS series were amorphous. Incorporating NDA and SA influenced the T g values of those polymers, from about 378C for PETG 30 S 40 to 898C for PETG 30 N 40 . Furthermore, the shrinkage of these amorphous copolyesters was more than 40% when the heating temperature was higher than the corresponding T g .

The effects of incorporating 5-tert-butylisophthalic acid ( t BI) and 1-3/1-4 cyclohexanedimethanol (CHDM) in the polymer chain of poly(ethylene terephthalate) (PET) on the crystallization behavior and thermal, optical and tensile properties of this polyester (PETGB) were evaluated. These random copolyesters that contained between 0 and 20 mol % of CHDM and between 0 and 10 mol % of t BI units were prepared by esterification followed by melt copolycondensation. The compositions and molecular weights of the copolyesters were determined by 1 H-NMR spectroscopy and viscometry, respectively. The composition of the polyester was consistent with the composition of the feed. The intrinsic viscosities of the copolymers ranged between 0.62 and 0.74 dL/g. The ther-mal behaviors were investigated over the entire range of copolymer compositions, using DSC under the heating and cooling rate of 208C/min and TGA. The copolyesters with t BI and CHDM of < 20 mol % were crystallizable, whereas the copolyesters with t BI and CHDM of 20 mol % were amorphous. They appeared to be stable up to 3958C. The optical transmissions of the amorphous polyesters were more than 88% in the visible region. The mechanical behavior was investigated by performing a tensile test.

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In this study, amorphous poly(ethylene terephthalate‐co‐1,3/1,4‐cyclohexylenedimethylene terephthalate) (PETG)/organoclay nanocomposites was synthesized by the in situ intercalation polymerization of terephthalic acid, ethylene glycol, 1,3/1,4‐cyclohexanedimethanol, and organoclay. The organoclay was obtained by modifying sodium montmorillonite (clay) with hexadecyl triphenylphosphonium bromide. The thermal, mechanical, optical, and gas barrier properties of these PETG nanocomposites with various organoclay contents (0–3 wt%) were discussed. The differential scanning calorimetry and X‐ray analyses revealed that all of the nanocomposites were amorphous. X‐ray diffraction and transmission electron micrographs showed that the organoclay was well dispersed in the polymer matrix, although some parts of the agglomerated layers remained on the scale of several hundreds of nanometers. The thermal stability and the mechanical property of the nanocomposites increased with organoclay content. The optical transmittances of nanocomposites that contained 0.5, 1, and 3 wt% of organoclay were 86.8%, 84.4%, and 77.4%, respectively. The oxygen transmission rate of the nanocomposite that contained 3 wt% of organoclay was about 50% of the PETG base polymer. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers