The heat capacity of poly(trimethylene terephthalate) (PTT) has been measured using adiabatic calorimetry, standard differential scanning calorimetry (DSC), and temperature‐modulated differential scanning calorimetry (TMDSC). The heat capacities of the solid and liquid states of semicrystalline PTT are reported from 5 to 570 K. The semicrystalline PTT has a glass transition temperature of 331 K. Between 340 and 480 K, PTT can show exothermic ordering depending on the prior degree of crystallization. The melting endotherm of semicrystalline samples occurs between 480 and 505 K, with a typical onset temperature of 489 K (216°C). The heat of fusion of the semicrystalline samples is about 15 kJ mol−1. For 100% crystalline PTT the heat of fusion is estimated to be 30 ± 2 kJ mol−1. The heat capacity of solid PTT is linked to an approximate group vibrational spectrum and the Tarasov equation is used to estimate the heat capacity contribution due to skeletal vibrations (θ1 = 550.5 K and θ2 = θ3 = 51 K, Nskeletal = 19). The calculated and experimental heat capacities agree to better than ±3% between 5 and 300 K. The experimental heat capacities of liquid PTT can be expressed by: \documentclass{article}\pagestyle{empty}\begin{document}$ C^L_p(exp) $\end{document} = 211.6 + 0.434 T J K−1 mol−1 and compare to ±0.5% with estimates from the ATHAS data bank using contributions of other polymers with the same constituent groups. The glass transition temperature of the completely amorphous polymer is estimated to be 310–315 K with a ΔCp of about 94 J K−1 mol−1. Knowing Cp of the solid, liquid, and the transition parameters, the thermodynamic functions enthalpy, entropy, and Gibbs function were obtained. With these data one can compute for semicrystalline samples crystallinity changes with temperature, mobile amorphous fractions, and resolve the question of rigid‐amorphous fractions.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2499–2511, 1998

A new family of terephthalate-based copolyesters has been found to exhibit high impact resistance combined with good thermal properties, ultraviolet stability, optical clarity, and low color. These engineering thermoplastic compositions were prepared using conformationally rigid cis/trans-2,2,4,4tetramethyl-1,3-cyclobutanediol [CBDO] and flexible C 2-C4 aliphatic glycols. The copolymers were amorphous when the CBDO (∼50/50 cis/trans) content was about 40 to 90 mol % of total diol. Glass transition temperatures were 80-168 °C, depending on the proportion of rigid CBDO units. Impact resistance was inversely proportional to CBDO content, and notched Izod values as high as 1000 J/m were obtained. Both high Tg (>100 °C) and high impact (250-750 J/m) can be realized simultaneously for compositions containing about 50-80 mol % CBDO. Accelerated weathering indicated good inherent resistance of 1,3-propanediol/CBDO copolyterephthalate to yellowing under ultraviolet radiation. Dibutyltin oxide was more effective for transesterification of CBDO with dimethyl terephthalate than other typical catalysts. Better color and higher molecular weights were obtained with this catalyst when the flexible diol was 1,3-propanediol or 1,4-butanediol rather than ethylene glycol.

Tensile drawing of poly(trimethylene terephthalate) (PTT) was studied at room temperature, 35, 50, and 75 °C. Instead of a typical increase in draw ratio with increasing temperature, the PTT draw ratio first increased, went through a maximum, and decreased; all occurred within a narrow range of temperature between T g and T g + 30 °C. This unusual drawing behavior was due to the onset of cold crystallization during hot drawing. The fast cold crystallization rate could become dominating at high draw temperature, impeding PTT drawability to the extent that it caused in situ ductile−brittle transition and draw failure. The crystal orientation function, f c , measured with wide-angle X-ray diffraction (WAXD), increased rapidly with draw, and saturated at f c ≈ 0.96. Four IR vibration modes at 933, 1037, 1358, and 1505 cm-1 wavenumbers were found to be sensitive to draw for dichroic ratio characterization. By combining WAXD and IR orientation measurements, transition moment vectors of three crystalline 933, 1358, and 1505 cm-1 vibrations were found to make 54°, 29°, and 45° angles to the c-chain axis. The 933 and 811 cm-1 CH2 rocking modes were used to estimate changes in PTT's methylene gauche conformation in drawing. The gauche content increased with increasing draw ratio; however, it is a unique function of the polymer's final crystallinity obtained through a combination of strain-induced and cold crystallizations irrespective of the draw temperatures.

The bulk isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) was studied using a differential scanning calorimeter. Avrami's theory was used to analyze the data. Based on crystallinity growth rate, Avrami rate constant, K, and crystallization half‐time, PTT's crystallization rate is between those of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) when compared at the same degree of undercooling. PBT has the highest crystallization rate with K in the order of 10−2 to 10−1 min−n. It is about an order of magnitude faster than PTT at 10−3 to 10−2 min−n, which in turn is an order of magnitude faster than PET with K of 10−4 to 10−2 min−n. Contrary to previous reports (PTT was not included in the study) that aromatic polyesters with odd numbers of methylene units were more difficult to crystallize than the even‐numbered polyesters, PTT did not fit in the prediction and did not follow the odd‐even effect.

No abstract

No abstract

No abstract

No abstract