• Fibers and Polymers
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• v.2 no.2
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• pp.75-80
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• 2001

The thermal degradation of poly(ethylene terephthalate-co-isophthalate)s (PETIs) is investigated by using isothermal thermogravimetric analysis at the temperature range of 280-31$0^{\circ}C$. The degradation rate of PETIs is increased as the mole ratio of ethylene isophthaloyl (EI) units in PETIs increases. The activation energies for the thermal degradation of poly(ethylene terephthalate), PETI(5/5), and poly(ethylene isophthalate) are 33.4, 16.6, and 8.9 kcal/mole, respectively. The degradation rate of PETIs is influenced by their volatile cyclic oligomer components formed during the polymerization and the thermal degradation. It is simulated by the rotational isomeric state model that the content of cyclic dimer in PETIs, which is the most volatile cyclic oligomer component, increases with the EI units in PETIs.

• Polymer(Korea)
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• v.24 no.2
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• pp.182-193
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• 2000

Molar cyclization equilibrium constant (K$_{x}$) of poly(alkylene terephthalate) (PAT) cyclics was calculated by the Monte Carlo simulation on the basis of rotational isomeric state (RIS) model. The experimental $K_{x}$ of PAT cyclics, which was not clearly explained by the Jacobson-Stockmayer theory and the method of Flory, Suter, and Mutter however, was explained well by the direct computational method with the reaction radius ${\gamma}$=0.5 < ${\gamma}^{2}$> $^{1/2}$. The effect of PAT conformation on $K_{x}$ of PAT cyclics was investigated by changing its statistical weight parameters, ${\sigma}_{1}$ and ${\sigma}_{2}{\cdot}K_{x}$ of PAT cyclics obtained by the direct computation method with various radii and the radius ${\gamma}$=0.5 < ${\gamma}^{2}$> $^{1/2}$ was slightly changed with ${\sigma}_{1}$ and ${\sigma}_{2}$. Consequently, it was concluded that $K_{x}$ of PAT cyclics is strongly dependent on the configuration of each PAT and affected by the change of its conformation to some extent.