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。     

Polyester nanocomposite fibers: comparison of their properties with poly(ethylene terephthalate) and poly(trimethylene terephthalate) (II)

Summary Two polyester nanocomposites were synthesized, one with poly(ethylene terephthalate) (PET) and the other with poly(trimethylene terephthalate) (PTT), by using organoclay. The in-situ interlayer polymerization method was used to disperse the organoclay in polyesters at different organoclay contents and at different draw ratios to produce monofilaments. The thermal stability and tensile mechanical properties increased with increasing organoclay content at a DR=1 . However, the values of the tensile mechanical properties of the hybrid fibers decreased with increasing DR. The reinforcing effects of the organoclay of the PET hybrid fibers were higher than those of the PTT hybrid fibers.     

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     

Crystallization kinetics of poly(trimethylene terephthalate)

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.     

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.     

Synthesis and characterization of poly(trimethylene terephthalate)/polyhedral oligomeric silsesquixanes nanocomposites

This article reports the preparation of poly(trimethylene terephthalate) (PTT)– polyhedral oligomeric silsesquioxanes (POSS) nanocomposites through in situ polymerization. The chemical structure of the PTT–POSS nanocomposites was characterized with Fourier‐transform infrared and nuclear magnetic resonance spectroscopies and the presence of POSS was further confirmed by the elemental analysis. The crystal structures as well as the position of POSS in the nanocomposites were ascertained by the X‐ray diffraction (XRD) studies. Thermal characterization studies showed the gradual decrease in the glass transition and melt crystallization temperatures. Though the thermal stability of the PTT was not affected by the incorporation of POSS, the amount of residues obtained from thermal degradation process was increased with an increase in the content of POSS. The tensile studies showed that the values of initial modulus and breaking strength were dramatically decreased with an increase in the content of POSS. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

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     

Cracking in poly(trimethylene terephthalate) spherulites

The crack behavior of poly(trimethylene terephthalate) spherulites was studied mainly by polarizing optical microscopy, along with scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition to the effects of temperature and constraining substrate, another important factor, film thickness, on the formation of crack was first put forward and investigated. The emergence of the first crack occurred at 120°C during cooling after crystallization at 190°C for the sample with a thickness of 31.0 μm. For the spherulites growing between glass sheets, it was interesting that the sample with a thickness of 26.0 μm exhibited the largest number of cracks measured per 200 μm of radius, whereas samples thicker than 100 μm or thinner than 1 μm did not induce the formation of crack. Also, spherulites growing between two polyimide and two Teflon sheets showed no crack. Glass sheets lubricated with silicon oil restrained the number of cracks but did not eliminate cracks. SEM revealed that the cracking was about 900 nm in width. In addition, the AFM results suggest that the cracks had a depth of at least 150 nm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Alkaline depolymerization of poly(trimethylene terephthalate)

The purpose of this study was to investigate the effects of reaction media, composition, and temperature on the rate of the alkaline depolymerization of poly(trimethylene terephthalate) (PTT). The alkaline depolymerization of PTT was carried out at 160–190°C in ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), ethylene glycol monobutyl ether (EGMBE), diethylene glycol monoethyl ether (DEGMEE), and a mixture of these solvents. During the reaction, PTT was quantitatively converted to disodium terephthalate and 1,3-propanediol. The alkaline depolymerization reaction rate constants were calculated based on the concentration of sodium carboxylate, which was equivalent to the molar amount of sodium hydroxide. The depolymerization rate of PTT was increased by increasing the reaction temperature and by adding ethereal solvents. Moreover, the depolymerization rate was significantly accelerated in the order of EG < DEG < TEG < EGMBE < DEGMEE. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 99–107, 2001     

The structure of poly(trimethylene terephthalate)

The determination of the crystalline structure of oriented fibres of poly(trimethylene terephthalate) is described. The unit cell is triclinic with the following parameters: $\text{a = 4.6}\text{A}\text{?}$, $\text{b = 6.2}\text{A}\text{?}$, $\text{c = 18.3}\text{A}\text{?}$, α = 98°, β = 90°, γ = 112°. Each cell contains two monomers of one polymer chain. Both methylene bonds are in the gauche conformation. The chain conformation and the packing of chains within the unit cell are discussed in detail and compared with other chemically similar materials, both monomeric and polymeric.     

Impact modification of poly(trimethylene terephthalate)/polypropylene blend nanocomposites: Fabrication and characterization

A poly(trimethylene terephthalate) (PTT)/polypropylene (PP) blend and the nanocomposites were prepared with and without the addition of a compatibilizer precursor [maleic anhydride grafted polypropylene (MAPP)]. A reactive route was used for the compatibilization with the addition of MAPP during melt blending in a batch mixer. Organically modified nanoclays were used as nanoscale reinforcements to prepare the blend nanocomposites. Mechanical tests revealed optimum performance characteristics at a PTT/PP blend ratio of 80 : 20. Furthermore, incorporation of nanoclays up to 3 wt % showed a higher impact strength and higher tensile strength and modulus in the blend nanocomposites compared to the optimized blend. The nanocomposite formation was established through X‐ray diffraction and transmission electron microscopy (TEM). Thermal measurements were carried out with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC thermograms revealed an increase in the crystallization temperature in the presence of the nanoclays in the blend system containing Cloisite 30B. TGA thermograms also indicated that the thermal stability of blend increased with the incorporation of Cloisite 30B. Furthermore, dynamic mechanical analysis measurements showed that the Cloisite 30B nanocomposite had the maximum modulus compared to other nanocomposites. TEM micrographs confirmed an intercalated morphology in the blend nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Banded spherulites of electrospun poly(trimethylene terephthalate)/carbon nanotube composite mats

The crystallization of poly(trimethylene terephthalate) (PTT) composites containing carbon nanotubes (CNTs) were studied in this work. The electrospinning technology was employed successfully to fabricate thin film samples with well‐embedded CNTs for spherulite observations using atom force microscopy. The results show that the composites present a higher overall crystallization rate than that of the neat PTT due to the nucleation effect of the CNTs. Banded spherulites can be observed on both the neat PTT and the composites. The presence of CNTs does not change the twisting mode of PTT crystal, but reduces band spacing and twist period. This is attributed to the enhanced fold staggering level of lamellae caused by the narrowed lamellae size and accelerated spherulite growth, which is further confirmed by analysis through secondary nucleation theory. Copyright © 2011 Society of Chemical Industry     

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.     

Nanocomposites of poly(trimethylene terephthalate) with organoclay

Two different kinds of clay were organomodified with cetylpyridinium chloride (CPC) as an intercalation agent. Poly(trimethylene terephthalate) (PTT)/organoclay nanocomposites were prepared by the solution intercalation method. Wide‐angle X‐ray diffraction (WAXD) indicated that the layers of clay were intercalated by CPC and the interlayer spacing was a function of the cationic exchange capacity (CEC) of the clay: the higher the CEC, the larger the interlayer spacing is. The WAXD studies showed that the interlayer spacing of organoclay in the nanocomposites depends on the amount of organoclay. From the results of differential scanning calorimetry analysis it was found that clay behaves as a nucleating agent and enhances the crystallization rate of PTT. The maximum enhancement of the crystallization rate for the nanocomposites was observed in nanocomposites containing about 5 wt % organoclay with a range of 1–15 wt %. The thermal stability of the nanocomposites was enhanced by the addition of 1–10 wt % organoclay as found from thermogravimetric analysis. The thermal stability of the PTT/organoclay nanocomposites was related to the organoclay content and the dispersion in the PTT matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3315–3322, 2003     

Miscibility and melting behavior of poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends

The miscibility and melting behavior of binary crystalline blends of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) have been investigated with differential scanning calorimetry and scanning electron microscope. The blends exhibit a single composition‐dependent glass transition temperature (T_g) and the measured T_g fit well with the predicted T_g value by the Fox equation and Gordon‐Taylor equation. In addition to that, a single composition‐dependent cold crystallization temperature (T_cc) value can be observed and it decreases nearly linearly with the low T_g component, PTT, which can also be taken as a valid supportive evidence for miscibility. The SEM graphs showed complete homogeneity in the fractured surfaces of the quenched PET/PTT blends, which provided morphology evidence of a total miscibility of PET/PTT blend in amorphous state at all compositions. The polymer–polymer interaction parameter, χ₁₂, calculated from equilibrium melting temperature depression of the PET component was ?0.1634, revealing miscibility of PET/PTT blends in the melting state. The melting crystallization temperature (T_mc) of the blends decreased with an increase of the minor component and the 50/50 sample showed the lowest T_mc value, which is also related to its miscible nature in the melting state. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

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     

Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization

Two series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (T_cm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (T_m) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the T_cm and T_m peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (T_g) irrespective of clay content, and a noticeable decrease in T_g with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Crystallization and melting behaviors of poly(trimethylene terephthalate)

The crystallization and melting behaviors of poly(trimethylene terephthalate) (PTT) have been studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and solid-state NMR. At certain crystallization temperatures (T_c) for a given time, the isothermally crystallized PTT exhibits two melting endotherms, which is similar to that of PET and PBT. At higher crystallization temperature (T_c = 210 °C), the low-temperature endotherm is related to the melting of the original crystals, while the high-temperature endotherm is associated with the melting of crystals recrystallized during the heating. The peak temperatures of these double-melting endotherms depend on crystallization temperature, crystallization time, and cooling rate from the melt as well as the subsequent heating rate. At a low cooling rate (0.2 °C/min) or a high heating rate (40 °C/min), these two endotherms tend to coalesce into a single endotherm, which is considered as complete melting without reorganization. WAXD results confirm that only one crystal structure exists in the PTT sample regardless of the crystallization conditions even with the appearance of double melting endotherms. The results of NMR reveal that the annealing treatment increases proton spin lattice relaxation time in the rotation frame, T_1ρ ^H, of the PTT. This phenomenon suggests that the mobility of the PTT molecules decreases after the annealing process. The equilibrium melting temperature (T _m ^o ) determined by the Hoffman-Weeks plot is 248 °C.     

Miscibility and crystallization kinetics of poly(trimethylene terephthalate)/amorphous poly(ethylene terephthalate) blends

The miscibility and crystallization kinetics of the blends of poly(trimethylene terephthalate) (PTT) and amorphous poly(ethylene terephthalate) (aPET) have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). It was found that PTT/aPET blends were miscible in the melt. Thus, the single glass transition temperature (T_g) of the blends within the whole composition range and the retardation of crystallization kinetics of PTT in blends suggested that PTT and aPET were totally miscible. The nucleation density of PTT spherulites, the spherulitic growth, and overall crystallization rates were depressed upon blending with aPET. The depression in nucleation density of PTT spherulites could be attributed to the equilibrium melting point depression, while the depression in the spherulitic growth and overall crystallization rates could be mainly attributed to the reduction of PTT chain mobility and dilution of PTT upon mixing with aPET. The underlying nucleation mechanism and growth geometry of PTT crystals were not affected by blending, from the results of Avrami analysis. POLYM. ENG. SCI., 47:2005–2011, 2007. © 2007 Society of Plastics Engineers