Effect of Carboxyl Terminal Groups on Crystallization Behavior of Poly(ethylene terephthalate)

In order to study the effect of carboxyl terminal groups on the crystallization behavior of poly(ethylene terephthalate) (PET), the concentration of carboxyl terminal groups and non-isothermal crystallization behavior of different relative molecular weight PET were investigated. The concentration of carboxyl terminal groups can be observed by infrared spectroscopy analysis (IR) and then be achieved by absorbance equation, the concentration of carboxyl terminal groups is gradually increasing along with relative molecular weight. Differential scanning calorimetry (DSC) observations for the PET illustrated that different relative molecular weight PET have more obvious difference in melting crystallization temperature (T-c), compared with cooling crystallization temperature (T-cc), glass transition temperature(T-g) and melting temperature(T-m). There is a relationship between concentration of carboxyl terminal groups and T-c, which is T-c = 0.2C(COOH)+164.67. The formation of a stable nucleus and crystallization behavior is relatively easy when the concentration of carboxyl terminal groups is higher.