Depolymerization of poly(trimethylene terephthalate) in supercritical methanol

The depolymerization of poly(trimethylene terephthalate) (PTT) in supercritical methanol was carried out with a batch‐type autoclave reactor at temperatures ranging from 280 to 340°C, at pressures ranging from 2.0 to 14.0 MPa, and for reaction time of up to 60 min. PTT quantitatively decomposed into dimethyl terephthalate (DMT) and 1,3‐propaniol (PDO) under the designed conditions. The yields of DMT and PDO greatly increased as the temperature rose. The yields of the monomers markedly increased as the pressure increased to 10.0 MPa, and they leveled off at higher pressures. The final yield of DMT at 320°C and 10.0 MPa reached 98.2%, which was much closer to the extent of the complete reaction. A kinetic model was used to describe the depolymerization reaction, and it fit the experimental data well. The dependence of the forward rate constant on the reaction temperature was correlated with an Arrhenius plot, which gave an activation energy of 56.8 kJ/mol. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2363–2368, 2004     

Thermal stability of poly(trimethylene terephthalate)

The first-order thermal degradation rates of poly(trimethylene terephthalate) [PTT] at 240-280 °C under non-oxidative conditions have been determined from the increase in allyl endgroups (¹H NMR) which closely match the rates determined from the decrease in molecular weight (intrinsic viscosity). Consequently, the predominant thermal degradation mechanism of PTT is consistent with concerted, electrocyclic oxo retro-ene chain cleavage under conditions pertinent to viable polymerization processes and efficient downstream extrusion and spinning into fiber. Although catalysts, additives and other reaction variables can influence the thermo-oxidative stability of polyesters including PTT, these factors have been found to have little or no effect on PTT thermal degradation rates under non-oxidative environments. The thermal stability of poly(butylene terephthalate) [PBT] has also been determined from butenyl endgroups (NMR) and molecular weight (IV). The activation energies (E_a) for both PTT and PBT thermal chain cleavage are similar to the reported E_as for poly(ethylene terephthalate) [PET] degradation, which is further supported by semi-empirical molecular orbital calculations on model compounds. However, both PTT and PBT undergo molecular weight decrease faster than PET. The apparent slower chain cleavage of PET is attributed to the contribution of productive chain propagation reactions due to unstable vinyl endgroups which alters the equilibrium stoichiometry compared to the relatively stable endgroups of PTT and PBT.     

Melting behavior of poly(trimethylene terephthalate)

In this study, the melting behavior of isothermally crystallized polytri‐ methylene terephthalate (PTT) was investigated. Multiple melting behaviors in DSC heating trace were found because two populations of lamellar stacks were formed during primary crystallization and the recrystallization at heating process, respectively. This fact could be also confirmed from the result of optical microscopy observation. The Hoffman–Weeks equation was applied to obtain equilibrium melting temperature (T). The T value of PTT is about 525 K, which is 10 K higher than that reported. Combining the enthalpy of fusion from the DSC result and the degree of crystallinity from WAXD result, the value of the equilibrium‐melting enthalpy ΔH was deduced to be approximately 28.8 kJ mol^?1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2426–2433, 2002     

Thermal properties and non‐isothermal crystallization behavior of poly(trimethylene terephthalate)/poly(lactic acid) blends

Thermal properties and non‐isothermal melt‐crystallization behavior of poly(trimethylene terephthalate) (PTT)/poly(lactic acid) (PLA) blends were investigated using differential scanning calorimetry and thermogravimetric analysis. The blends exhibit single and composition‐dependent glass transition temperature, cold crystallization temperature (T_cc) and melt crystallization peak temperature (T_mc) over the entire composition range, implying miscibility between the PLA and PTT components. The T_cc values of PTT/PLA blends increase, while the T_mc values decrease with increasing PLA content, suggesting that the cold crystallization and melt crystallization of PTT are retarded by the addition of PLA. The modified Avrami model is satisfactory in describing the non‐isothermal melt crystallization of the blends, whereas the Ozawa method is not applicable to the blends. The estimated Avrami exponent of the PTT/PLA blends ranges from 3.25 to 4.11, implying that the non‐isothermal crystallization follows a spherulitic‐like crystal growth combined with a complicated growth form. The PTT/PLA blends generally exhibit inferior crystallization rate and superior activation energy compared to pure PTT at the same cooling rate. The greater the PLA content in the PTT/PLA blends, the lower the crystallization rate and the higher the activation energy. Moreover, the introduction of PTT into PLA leads to an increase in the thermal stability behavior of the resulting PTT/PLA blends. Copyright © 2011 Society of Chemical Industry     

Study on the macrokinetics of poly(trimethylene terephthalate) polycondensation reaction

The macrokinetics of poly(trimethylene terephthalate) (PTT) polycondensation reaction during the high‐vacuum process was studied. The results showed that PTT polycondensation reaction may be considered as a second‐order reaction and thermal degradation is negligible in mathematical handling. The intrinsic viscosity versus time undergoes two different processes according to temperature. The apparent reaction rate constants and apparent activation energy of PTT polycondensation reaction are smaller than those of PET. Under efficient stirring, PTT polycondensation reaction is still reaction‐controlled and the role of devolatilization could be neglected even during the high‐vacuum process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1765–1770, 2004     

Isothermal gravimetric analysis of poly(trimethylene terephthalate)

Poly(trimethylene terephthalate) was investigated by isothermal thermogravimetry in nitrogen at six temperatures, including 304, 309, 314, 319, 324, and 336°C. The isothermal data have been analyzed using both a peak maximum technique and an iso‐conversional procedure. Both techniques gave apparent activation energies of 201 and 192 kJ mol^?1, respectively, for the isothermal degradation of poly(trimethylene terephthalate) in nitrogen. The decomposition reaction order is calculated to be 1.0. The natural logarithms of the frequency factor based on the peak maximum and the iso‐conversional techniques are 36 and 34 min^?1, respectively, for poly(trimethylene terephthalate) decomposed isothermally in nitrogen. These isothermal kinetic parameters are in good agreement with those derived by the Kissinger technique on the basis of the dynamic thermogravimetric data reported elsewhere (209 kJ mol^?1, 1.0 and 37 min^?1). The isothermal decomposition of poly(trimethylene terephthalate) in nitrogen undergoes two processes, a relative fast degradation process in the initial period and a subsequent one with a slower weight‐loss rate. The former process may be due to the removal of ester groups, trimethylene groups, and aromatic hydrogen atoms from the chain of poly(trimethylene terethphalate). The latter one may be ascribed to the further pyrolysis of the carbonaceous char. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1600–1608, 2002; DOI 10.1002/app.10476     

High birefringence of poly(trimethylene terephthalate) spherulite

Poly(trimethylene terephthalate) (PTT) spherulite shows interference color under polarized light microscope without a sensitive tint plate. The fact indicates that the retardation of PTT spherulite is high, while it was reported that the birefringence in PTT fiber is low. In this study, the reason why the high birefringence is observed in PTT spherulite was discussed. By small area X-ray diffraction measurement, it was confirmed that a-axis of unit cell of PTT crystal was parallel to the radial direction of the spherulite. Based on the result, we calculated the refractive indices of parallel to a-axis and the other orthogonal directions. It was clarified that the refractive index of a-axis is much lower than the others and the intrinsic birefringence for a-axis orientation is high. It is the reason why the PTT spherulite shows high and negative birefringence.     

Thermal decomposition kinetics of thermotropic poly(oxybenzoate‐co‐trimethylene terephthalate)

A new kind of thermotropic liquid crystalline, poly(oxybenzoate‐co‐trimethylene terephthalate), was prepared from p‐hydroxybenzoic acid (B) and poly(trimethylene terephthalate) (PTT or T) by melting polycondensation. The monomer ratio of B to T is 60:40. The dynamic thermogravimetric kinetics of the copolymer B/T (60:40) and PTT in nitrogen were analyzed by four single heating rate techniques and two multiple heating rate techniques. The effects of the heating rate and the calculating technique on the thermostable and degradation kinetic parameters of the B/T copolymer and PTT are systematically discussed. The four single heating rate techniques used in this work include Friedman, Freeman‐Carroll, Chang, and the second Kissinger techniques, whereas the two multiple heating rate techniques are the first Kissinger and Flynn‐Wall techniques. Additionally, the isothermal thermogravimetric kinetics of B/T (60:40) in nitrogen were investigated by the Flynn technique. The activation energy, the order, and the frequency factor of the degradation reaction for B/T (60:40) copolymer are determined to be 185 kJ/mol, 1.8, and 7.14 × 10¹³ min⁻¹, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2025–2036, 2000     

Crystallization behavior and morphology of double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers

Double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers (PTT/PEOT), with PTT content ranging from 16.5 to 65.5 wt%, were synthesized by melt copolycondensation. The morphological transformation of samples from microphase separation to macrophase separation was investigated by gel permeation chromatography and transmission electron microscopy. Differential scanning calorimetry and in situ wide‐angle X‐ray diffraction suggested that all copolycondensation samples displayed double crystalline behavior. The melt‐crystallization peak temperatures (T_{m, c} values) of PTT chains monotonously increased with increasing PTT content and were higher than that of homo‐PTT when the content of PTT was above 30.6 wt%. Interestingly, T_{m, c} values of PEOT chains were also increased with increasing PTT content. Polarized optical microscopy revealed that all copolycondensation samples studied could form ring‐banded spherulites and band spacing increased with increasing T_c values. In addition, band spacing decreased with increasing PTT content at a given T_c. Strangely, although PEOT was the main component in all copolycondensation samples, spherulitic morphology formed by the advance crystallization of PTT did not change after PEOT crystallization. Only a subtle change of quadrant tones was detected. © 2012 Society of Chemical Industry     

Nanofibrous mats of poly(trimethylene terephthalate) via electrospinning

Nanofibrous mats were prepared by electrospinning of poly(trimethylene terephthalate) (PTT) with diameter ranging from 200 to 600 nm. Morphology of electrospun nanofiber obtained by changing processing parameters such as solution concentration and their deposition time, was investigated with scanning electron microscope (SEM). Especially, periodic feature of surface roughness, such as diamond-shaped structure, was exhibited as the deposition time increased. In this work, it was shown that this phenomenon might result from polymer chain mobility, which was induced by solvent properties, and point bonding structure. In addition, schematic diagram was introduced to identify the formation of diamond-shape structure in PTT electrospun nanofibrous mats.     

Crystallization kinetics and morphology of poly(trimethylene terephthalate)

In this work, the isothermal crystallization kinetics of polytrimethylene terephthalate (PTT) was first investigated from two temperature limits of melt and glass states. For the isothermal melt crystallization, the values of Avrami exponent varied between 2 and 3 with changing crystallization temperature, indicating the mixed growth and nucleation mechanisms. Meanwhile, the cold crystallization with an Avrami exponent of 5 indicated a character of three-dimensional solid sheaf growth with athermal nucleation. Through the analysis of secondary nucleation theory, the classical regime I→II and regime II→III transitions occurred at the temperatures of 488 and 468 K, respectively. The average work of chain folding for nucleation was ca. 6.5 kcal mol⁻¹, and the maximum crystallization rate was found to be located at ca. 415 K. The crystallite morphologies of PTT from melt and cold crystallization exhibited typical negative spherulite and sheaf-like crystallite, respectively. Moreover, the regime I→II→III transition was accompanied by a morphological transition from axialite-like or elliptical-shaped structure to banded spherulite and then non-banded spherulite, indicating that the formation of banded spherulite is very sensitive to regime behavior of nucleation.     

PTT树脂及其开发进展

综述了聚对苯二甲酸丙二酯(PTT)树脂的合成工艺、性能及应用,并介绍了近年来PTT树脂研究开发的新进展.     

聚对苯二甲酸丙二醇酯的热性能研究

研究了聚对苯二甲酸丙二醇酯 (PTT) ,PET ,CDP在不同温度和时间下的特性粘数和端羧基含量的变化。结果表明 ,一定温度下 ,PTT熔体特性粘数随熔融时间的延长而下降 ,一定时间下 ,随温度的升高而下降。PTT端羧基含量随温度升高而增大 ,PTT的热稳定性较PET明显下降。     

Effects of reprocessing on the structure and mechanical properties of poly(trimethylene terephthalate)

The effects of reprocessing by extrusion for up to four cycles on the structure and mechanical properties of poly(trimethylene terephthalate) (PTT) were studied. Reprocessing did not change the chemical structure of the polymer but led to both yellowing and molecular weight reduction. Young's modulus and the yield stress of PTT remained constant or decreased with successive extrusion cycles, probably because of the observed slight specific volume increase. The continuous reduction in the break properties due to reprocessing was smaller than that found in similar polyesters and was attributed to the molecular weight reduction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2775–2780, 2002     

Rheological properties of poly(trimethylene terephthalate) in capillary flow

The shear viscosity, extensional viscosity, and die swell of the PTT melt were investigated using a capillary rheometer. The results showed that the PTT melt was a typical pseudoplastic fluid exhibiting shear thinning and extensional thinning phenomena in capillary flow. There existed no melt fracture phenomenon in the PTT melt through a capillary die even though the shear rate was 20,000 s^?1. Increasing the shear rate would decrease the flow activation energy and decline the sensitivity of the shear viscosity to the melt temperature. The molecular weight had a significant influence on the flow curve. The flow behavior of the PTT melt approached that of Newtonian fluid even though the weight‐molecular weight was below 43,000 s^?1 at 260°C. The extensional viscosity decreased with the increase of the extensional stress, which became more obvious with increasing the molecular weight. The sensitiveness of the extensional viscosity to the melt temperature decreased promptly along with increasing the extensional strain rate. The die swell ratio and end effect would increase along with increasing the shear rate and with decreasing the temperature, which represented that the increase of the shear rate and the decrease of temperature would increase the extruding elasticity of the PTT melt in the capillary die. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 705–709, 2005     

PTT长丝瞬时拉伸回弹性能研究

在相同条件下对比研究了PET ,PTT和PBT 3种芳香族聚酯长丝的瞬时拉伸回弹性能 ,分析了测定条件对PTT长丝瞬时拉伸回弹性能的影响 ,并初步讨论了 3种芳香族聚酯长丝的瞬时拉伸回弹机理。结果表明 ,PTT长丝的瞬时拉伸回弹性能明显优于PBT长丝 ,更优于PET长丝 ,PTT长丝在低伸长率和高伸长率下均具有优异的瞬时拉伸回弹性能 ;测定PTT长丝瞬时拉伸回弹率时 ,建议采用 0 .5cN/tex的预张力 ,5 0 0mm/min的拉伸速率和 2 0 %的定伸长率等条件     

Phase morphology and clay distribution of poly(trimethylene terephthalate)/polypropylene/montmorillonite nanocomposites

Poly(trimethylene terephthalate) (PTT)/polypropylene (PP) blend nanocomposites were prepared by melt mixing of PTT, PP, and organically modified clay. The phase morphologies of the PTT/PP nanocomposites and the distribution of the clay in the nanocomposites were investigated using scanning electron microscopy, transmission electron microscopy (TEM), and wide angle X‐ray diffraction. When PP is the dispersed phase, the domain size of the PP phase is decreased significantly with increasing the clay content from 0 to 5 wt %. In contrast, when PTT is the dispersed phase, the dimension of the PTT phase is a little larger in the presence of 2 wt % clay compared with the case of without clay. TEM observations indicate that the clay is mainly distributed at the phase interfaces along the phase borderlines. In addition, some intercalated clay tactoids (multilayer particles) are observed in the PTT matrix whereas no discernable clay particles can be found in the PP phase, indicating that the affinity of clay with PTT is higher than with PP. In the presence of 5 wt % PP‐graft‐maleic anhydride, the phase morphology is much finer, and most clay is exfoliated and distributed at the phase interfaces forming phase borderlines in polygonal shape. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

草酸亚锡催化合成PTT的研究

采用对苯二甲酸(PTA)和1,3-丙二醇(1,3-PDO)为原料,以自制的草酸亚锡为催化剂经酯化、缩聚,制得聚对苯二甲酸丙二醇酯(PTT)。探讨了反应条件对合成反应的影响。结果表明:草酸亚锡的催化活性优于丁基锡酸和辛酸亚锡。1,3-PDO／PTA的摩尔比为1．5／1、草酸亚锡用量为5×10-4mol／mol(相对PTA),酯化反应温度260℃,反应时间2 h;缩聚反应温度260℃,反应时间2 h,可制得PTT,其特性粘数为0．8950dL／g,端羧基含量为15 mol／t。     

Crystallization, and morphology of poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) segmented block copolymers

A new type of poly(ether-ester) based on poly(trimethylene terephthalate) as rigid segments and poly(ethylene oxide terephthalate) as soft segments was synthesized and its crystallization behavior and morphology were investigated. Differential Scanning Calorimetry revealed that the copolymer containing 57 wt% soft segments presented a low glass transition temperature (−46.4 °C) and a high melting temperature (201.8 °C), suggesting that it had the typical characteristic of thermoplastic elastomer. With increasing soft segment content from 35 to 57 wt%, the crystallization morphology transformed from banded spherulites to compact seaweed morphology at a certain film thickness, which was due to the change of surface tension and diffusivity caused by increasing the soft segment content. Moreover, with the decrease of film thickness from 15 to 2 μm, the crystallization morphology of the copolymer (57 wt% soft segment) changed from wheatear-like, compact seaweed to dendritic. Scanning Electron Microscopy revealed that some flower-like crystals presenting in the bulk, which had been surprisingly found in the poly(ether-ester) segmented block copolymers for the first time. Possible mechanism was discussed in the text.     

1,3-丙二醇钛催化合成PTT的工艺研究

以自制的1,3-丙二醇钛为催化剂,采用对苯二甲酸(PTA)和1,3-丙二醇(PDO)为原料,通过直接酯化法制得聚对苯二甲酸丙二醇酯(PTT);研究了催化剂用量、反应物配比、酯化和缩聚温度、缩聚时间等对反应结果的影响.结果表明:以1,3-丙二醇钛为催化剂制备PTT是可行的;在酯化反应温度为230～235℃,PDO/PTA...