Binary and ternary blends of high‐density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials

Binary blends of recycled high‐density polyethylene (R‐HDPE) with poly(ethylene terephthalate) (R‐PET) and recycled polystyrene (R‐PS), as well as the ternary blends, i.e. R‐HDPE/R‐PET/R‐PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R‐HDPE/R‐PET and R‐HDPE/R‐PS blends show phase inversion but at different compositions. The R‐PET was found to have much higher influence on the properties enhancement of the R‐HDPE compared to R‐PS, but at the phase inverted situation, a significant loss in the tensile strength of R‐HDPE/R‐PET blend was observed due to the weak interaction at this morphological state. However, the ternary blends with higher loading of second phase, namely greater than 50 wt% of R‐PET+R‐PS, demonstrated better mechanical properties than the binary blends with the same content of either R‐PET or R‐PS. Copyright © 2009 John Wiley & Sons, Ltd.     

Morphology,structure, and properties of in situ compatibilized linear low‐density polyethylene/polystyrene and linear low‐density polyethylene/high‐impact polystyrene blends

Blends of linear low‐density polyethylene (LLDPE) with polystyrene (PS) and blends of LLDPE with high‐impact polystyrene (HIPS) were prepared through a reactive extrusion method. For increased compatibility of the two blending components, a Lewis acid catalyst, aluminum chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction between the blending components. Spectra data from Raman spectra of the LLDPE/PS/AlCl₃ blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of the benzene rings of PS, and this confirmed the graft structure of the Friedel–Crafts reaction between the polyolefin and PS. Because the in situ generated LLDPE‐g‐PS and LLDPE‐g‐HIPS copolymers acted as compatibilizers in the relative blending systems, the mechanical properties of the LLDPE/PS and LLDPE/HIPS blending systems were greatly improved. For example, after compatibilization, the Izod impact strength of an LLDPE/PS blend (80/20 w/w) was increased from 88.5 to 401.6 J/m, and its elongation at break increased from 370 to 790%. For an LLDPE/HIPS (60/40 w/w) blend, its Charpy impact strength was increased from 284.2 to 495.8 kJ/m². Scanning electron microscopy micrographs showed that the size of the domains decreased from 4–5 to less than 1 μm, depending on the content of added AlCl₃. The crystallization behavior of the LLDPE/PS blend was investigated with differential scanning calorimetry. Fractionated crystallization phenomena were noticed because of the reduction in the size of the LLDPE droplets. The melt‐flow rate of the blending system depended on the competition of the grafting reaction of LLDPE with PS and the degradation of the blending components. The degradation of PS only happened during the alkylation reaction between LLDPE and PS. Gel permeation chromatography showed that the alkylation reaction increased the molecular weight of the blend polymer. The low molecular weight part disappeared with reactive blending. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1837–1849, 2003     

Processing of high density polyethylene and poly(ethylene terephthalate) blends

Commercial grades of high density polyethylene, HDPE and waste poly(ethylene terephthalate), PET were melt blended over a wide range of compositions. Effect of ethylene acrylic acid copolymer, EAA, ethylene vinyl acetate copolymer, EVA and maleic anhydride grafted EVA as compatibilizers on rheology and mechanical properties of the blend was studied. EAA was found most suitable compatibilizer.     

Crystallization behavior and morphology of poly(ethylene‐co‐trimethylene terephthalate)s

The melt crystallization behaviors and crystalline structures of poly(ethylene terephthalate) (PET), poly(trimethylene terephthalate), and poly(ethylene‐co‐trimethylene terephthalate) (PETT) were investigated with differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction at various crystallization temperatures (T_cs). The PETT copolymers were synthesized via the polycondensation of terephthalate with ethylene glycol and trimethylene glycol (TG) in various compositions. The copolymers with 69.0 mol % or more TG or 31.0 mol % or less TG were crystallizable, but the other copolymers containing 34–56 mol % TG were amorphous. The DSC isothermal results revealed that the addition of a small amount of flexible TG (up to 21 mol %) to the PET structure slightly reduced the formation of three‐dimensional spherulites. A greater TG concentration (91–100%) in the copolyesters changed the crystal growth from two‐dimensional to three‐dimensional. The DSC heating scans after the completion of isothermal crystallization at various T_cs showed three melting endotherms for PET, PETT‐88, PETT‐84, and PETT‐79 and four melting endotherms for PETT‐9 and PETT. The presence of an additional melting endotherm could be attributed to the melting of thinner and imperfect copolyester crystallites. Analyses of the Lauritzen–Hoffman equation demonstrated that PETT‐88 had the highest values of the product of the lateral and folding surface free energies, and this suggested that the addition of small amounts of flexible trimethylene terephthalate segments to PET disturbed chain regularity, thus increasing molecular chain mobility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4255–4271, 2004     

Nonisothermal crystallization behavior, and morphology of poly(trimethylene terephthalate)/polyethylene glycol copolymers

Poly(trimethylene terephthalate)/polyethylene glycol (PTT/PEG) copolymers, with PEG content ranging from 27.2 to 47.4 wt%, were synthesized by melt copolycondensation. Wide-Angle X-ray diffractometer revealed that all copolymers had the same crystal structure of homo-PTT at room temperature. All copolymers could form ring-banded spherulites, and band spacing increased with increasing PEG content at a given crystallization temperature. Nonisothermal crystallization morphology of copolymers was greatly influenced by cooling rate. When the cooling rate was 2.5 °C/min or lower, banded patterns were absent, whereas when the cooling rate was 20 °C/min or higher, a novel crystal morphology composed of non-banded spherulites (central part) and ring-banded spherulites with decreasing band spacing along the radial growth direction was observed. Moreover, the size of the non-banded spherulitic part decreased with increasing cooling rate. Finally, the nonisothermal crystallization kinetics of copolymers were analyzed and only the Mo method was satisfactory to accurately describe this system.     

Thermal,crystallization, mechanical,and rheological characteristics of poly(trimethylene terephthalate)/poly(ethylene terephthalate) blends

Blends of poly(trimethylene terephthalate) (PTT) and poly(ethylene terephthalate) in the amorphous state were miscible in all of the blend compositions studied, as evidenced by a single, composition‐dependent glass‐transition temperature observed for each blend composition. The variation in the glass‐transition temperature with the blend composition was well predicted by the Gordon–Taylor equation, with the fitting parameter being 0.91. The cold‐crystallization (peak) temperature decreased with an increasing PTT content, whereas the melt‐crystallization (peak) temperature decreased with an increasing amount of the minor component. The subsequent melting behavior after both cold and melt crystallizations exhibited melting point depression behavior in which the observed melting temperatures decreased with an increasing amount of the minor component of the blends. During crystallization, the pure components crystallized simultaneously just to form their own crystals. The blend having 50 wt % of PTT showed the lowest apparent degree of crystallinity and the lowest tensile‐strength values. The steady shear viscosity values for the pure components and the blends decreased slightly with an increasing shear rate (within the shear rate range of 0.25–25 s^?1); those of the blends were lower than those of the pure components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 676–686, 2004     

Nonisothermal cold‐crystallization kinetics of poly(trimethylene terephthalate)

The nonisothermal cold‐crystallization kinetics and subsequent melting behavior of poly(trimethylene terephthalate) (PTT) were investigated with differential scanning calorimetry. The Avrami, Tobin, and Ozawa equations were applied to describe the kinetics of the crystallization process. Both the Avrami and Tobin crystallization rate parameters increased with the heating rate. The Ozawa crystallization rate increased with the temperature. The ability of PTT to crystallize from the glassy state at a unit heating rate was determined with Ziabicki's kinetic crystallizability index, which was found to be about 0.89. The effective energy barrier describing the nonisothermal cold‐crystallization process of PTT was estimated by the differential isoconversional method of Friedman and was found to range between about 114.5 and 158.8 kJ mol^?1. In its subsequent melting, PTT exhibited double‐melting behavior for heating rates lower than or equal to 10 °C min^?1 and single‐melting behavior for heating rates greater than or equal to 12.5 °C min^?1. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4151–4163, 2004     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Melt-crystallization behavior and isothermal crystallization kinetics of crystalline/crystalline blends of poly(ethylene terephthalate)/poly(trimethylene terephthalate)

The melt-crystallization and isothermal melt-crystallization kinetics of poly(ethylene terephthalate)/poly(trimethylene terephthalate) blends (PET/PTT) were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy. Although PET and PTT in the binary blends are miscible at amorphous state, they will crystallize individually when cooled from the melt. In the DSC measurements, PET component with higher supercooling degree will crystallize first, and then the crystallite of PET will be the nucleating agent for PTT, which induce the crystallization of PTT at higher temperature. On the other hand, in both blends of PET80/PTT20 and PET60/PTT40, the PET component will crystallize at higher temperature with faster crystallization rate due to the dilute effect of PTT. So the commingled minor addition of one component to another helps to improve the crystallization of the blends. For blends of PET20/PTT80 and PET40/PTT60, isothermal crystallization kinetics evaluated in terms of the Avrami equation suggest different crystallization mechanisms occurred. The more PET content in blends, the fast crystallization rate is. The Avrami exponent, n = 3, suggests a three-dimensional growth of the crystals in both blends, which is further demonstrated by the spherulites formed in all blends. The crystalline blends show multiple-melting peaks during heating process.     

Transreactions in poly trimethylene terephthalate/bisphenol-A polycarbonate (PC) blends analysed by pressure-volume-temperature measurements

The effect of annealing on the miscibility and thermal properties of poly trimethylene terephthalate (PTT)/bisphenol-A polycarbonate (PC) blends was examined using pressure-volume-temperature (PVT) measurements. The PTT/PC blends were thermally annealed at 260 °C for different times to induce various extents of transesterification reactions between the two polymers. The non-annealed blends are immiscible and exhibit the thermal properties of the blend components. Upon annealing, the original semi-crystalline morphology transforms to an increasingly amorphous nature. PVT and WAXS analysis confirmed that the PTT/PC blends completely lost their crystallinity when annealed at 260 °C for a period of 120 min or longer, indicating the formation of random co-polyesters due to chemical transreactions between the PTT and PC. The further increase in the specific volume with annealing time also indicates that after reaching a completely amorphous co-polymer the transesterification continuous until a fully random copolymer is formed.     

Miscibility and thermal properties of melt‐mixed poly(trimethylene terephthalate)/amorphous copolyester blends

This work examined the miscibility, crystallization kinetics, and melting behavior of melt‐mixed poly(trimethylene terephthalate) (PTT)/poly(ethylene‐co‐cyclohexane 1,4‐dimethanol terephthalate) (PETG) blends. Differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction techniques were used to approach the goals. The single composition‐dependent glass‐transition temperatures of the blends and the equilibrium melting temperature (T) depression of PTT in the blends indicated the miscible characteristic of the blend system at all compositions. T of pure PTT, determined with a conventional extrapolative method, was 525.8 K. Furthermore, the Flory–Huggins interaction parameter was estimated to be ?0.38. The dynamic and isothermal crystallization abilities of PTT were hindered by the incorporation of PETG. A complex melting behavior was observed for pure PTT and its blends. The observed complex melting behavior resulted mainly from the recrystallization and/or reorganization of the originally formed crystals during the heating scans. For the samples crystallized under the same conditions, the degree of recrystallization and/or reorganization declined with increasing PETG contents in the blends. The preliminary results obtained from the DSC experiments suggested that untraceable interchange reactions occurred in the studied blends. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2264–2274, 2003     

Stress–strain behavior of low‐density polyethylene/poly(methyl methacrylate) blends with modulated interfaces with a hydrogenated polybutadiene‐block‐poly(methyl methacrylate) diblock copolymer

The stress–strain diagrams and ultimate tensile properties of uncompatibilized and compatibilized hydrogenated polybutadiene‐block‐poly(methyl methacrylate) (HPB‐b‐PMMA) blends with 20 wt % poly(methyl methacrylate) (PMMA) droplets dispersed in a low‐density polyethylene (LDPE) matrix were studied. The HPB‐b‐PMMA pure diblock copolymer was prepared via controlled living anionic polymerization. Four copolymers, in terms of the molecular weights of the hydrogenated polybutadiene (HPB) and PMMA sequences (22,000–12,000, 63,300–31,700, 49,500–53,500, and 27,700–67,800), were used. We demonstrated with the stress–strain diagrams, in combination with scanning electron microscopy observations of deformed specimens, that the interfacial adhesion had a predominant role in determining the mechanism and extent of blend deformation. The debonding of PMMA particles from the LDPE matrix was clearly observed in the compatibilized blends in which the copolymer was not efficiently located at the interface. The best HPB‐b‐PMMA copolymer, resulting in the maximum improvement of the tensile properties of the compatibilized blend, had a PMMA sequence that was approximately half that of the HPB block. Because of the much higher interactions encountered in the PMMA phase in comparison with those in HPB (LDPE), a shorter sequence of PMMA (with respect to HPB but longer than the critical molecular weight for entanglement) was sufficient to favor a quantitative location of the copolymer at the LDPE/PMMA interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 22–34, 2005     

Crystallization‐induced aging in poly(trimethylene terephthalate)/ poly(ethylene oxide terephthalate) segmented block copolymers

A new type poly(ether–ester) based on poly(trimethylene terephthalate) as rigid segments and poly(ethylene oxide terephthalate) as soft segments was synthesized and its aging behavior were investigated. Different from other polymer, the segmented block copolymers exhibited a unique aging mechanism. That is, the degradation of mechanical property within short term annealing was due to the overgrown crystals and dramatically increased crystallinity, which was proved by field emission scanning electron microscope (FE‐SEM) and differential scanning calorimetry (DSC), respectively. The deterioration in mechanical property after long term annealing was the results of both the increase in crystallinity and the decrease in molecular weight. Moreover, FE‐SEM showed many interesting flower‐like crystals presented on the surface of annealed sample. The flower‐like crystals consist of several radialized petal‐like arms and a more densely packed center, which has been seldom found in polymer bulk. Wide‐angle x‐ray diffraction results showed that the copolymer has the same crystal structure as PTT. Such poly(ether–ester) or its blends with other polymer could be suitable for rapid degradable products, such as package and vessel. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 411–416, 2010     

Rheology of multi‐walled carbon nanotube/poly(butylene terephthalate) composites

Multi‐walled carbon nanotube/Poly(butylene terephthalate) nanocomposites (PCTs) were prepared by melt compounding. The microstructure of PCTs was investigated using transmission electron micrographs and Fourier transform infra‐red spectrometer. The linear and nonlinear as well as transient rheological properties of PCTs were characterized by the parallel plate rheometer. The results reveal that the surface modification can improve the dispersion state of nanotube in matrix. PCTs present a low percolation threshold of about 1–2 wt % in contrast to that of Poly‐(butylene terephthalate)/clay nanocomposites. The network structure is very sensitive to both the quiescent and large amplitude oscillatory shear deformation, and is also to the temperature, which makes the principle of time‐temperature superposition (TTS) be valid on PCTs only in a very restricted temperature range. The stress overshoots to the reverse flow are strongly dependent on both the rest time and shear rate but show a strain‐scaling response to the startup of steady shear, indicating that the broken network can reorganize even under quiescent condition. The nanotube may experience the long‐range, more or less order during annealing process. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2239–2251, 2007     

Thermoplastic elastomer based on high‐density polyethylene/natural rubber blends: rheological,thermal, and morphological properties

Thermoplastic elastomer (TPE) comprising air‐dried sheet or natural rubber (ADS or NR) and high‐density polyethylene (HDPE) was prepared by a simple blending technique. NR and HDPE were mixed with each type of phenolic compatibilizer (HRJ‐10518 or SP‐1045) or liquid natural rubber (LNR) at 180°C in an internal mixer. The mixing torque, shear stress, and shear viscosity of the blends increased with increasing amounts of NR. Positive deviation blend (PDB) for the blends containing active hydroxyl methyl phenolic resin in HRJ‐10518 or dimethyl phenolic resin in SP‐1045 was obtained. PDB was not observed for the blends without the compatibilizers or with LNR. The blends with HRJ‐10518 or SP‐1045 were compatible or partially compatible while the LNR blends were incompatible. In the phenolic compatibilized blends, NR dispersed in the HDPE matrix was found in the NR/HDPE blends of 20/80, 40/60, and 50/50 ratios. HDPE dispersed in NR matrix was obtained in the NR/HDPE blend of 80/20 ratio, and the co‐continuous phase was accomplished in the NR/HDPE blend of 60/40 ratio. The NR/HDPE blend at 60/40 ratio compatibilized with HRJ‐10518 and fabricated by a simple plastic injection molding machine exhibited higher ultimate tensile strength and elongation at break (EB). Incorporation of parafinic oil caused a decreasing tendency in tensile strength with increases in EB. The TPNRs exhibited high elastomeric nature with low‐tension set. Copyright © 2007 John Wiley & Sons, Ltd.     

Rheology, morphology and mechanical properties of polyethylene/ethylene vinyl acetate copolymer (PE/EVA) blends

Rheology, morphology and mechanical properties of binary PE and EVA blends together with their thermal behavior were studied. The results of rheological studies showed that, for given PE and EVA, the interfacial interaction in PE-rich blends is higher than EVA-rich blends, which in turn led to finer and well-distributed morphology in PE-rich blends. Using two different models, the phase inversion composition was predicted to be in 45 and 47 wt% of the PE phase. This was justified by morphological studies, where a clear co-continuous morphology for 50/50 blend was observed. The tensile strength for PE-rich blends showed positive deviation from mixing rule, whereas the 50/50 blend and EVA-rich blends displayed negative deviation. These results were in a good agreement with the results of viscoelastic behavior of the blends. The elongation at break was found to follow the same trend as tensile strength except for 90/10 PE/EVA blend. The latter was explained in terms of the effect of higher co-crystallization in 90/10 composition, which increased the tensile strength and decreased the elongation at break in this composition. The results of thermal behavior of the blends indicated that the melting temperatures of PE and EVA decrease and increase, respectively, due to the dilution effect of EVA on PE and nucleation effect of PE on EVA.     

Properties and morphology of recycled poly(ethylene terephthalate)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends by low‐temperature solid‐state extrusion

Among the various methods available for recycling plastics waste, blending technology is a straightforward and relatively simple method for recycling. In this paper, a new blending technology, low‐temperature solid‐state extrusion, was discussed. Several recycled poly(terephthalate ethylene)/bisphenol a polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends (R‐PET/PC/SEBS blends) have been prepared by this technology. The results show that thermal and hydrolytic degradation of R‐PET is improved when extruding temperature was between the glass transition temperature (T_g) and cold crystallization temperature (T_cc). Elongation at break and notched impact strength were increased evidently, from 15.9% to 103.6, and from 8.6 kJ/m² to 20.4 kJ/m², respectively. The appropriate rotating speed of screws was between 100 and 150 rpm. At the same time, the appropriate rotating speed of the screws brings a suitable shear viscosity ratio of R‐PET and PC, which is of advantage to blending of R‐PET and PC together with SEBS. Dispersion of minor phase, PC and SEBS, became finer and smaller, to about 1 µm. Chain extender, Methylenediphenyl diisocyanate (MDI) can react with the end‐carboxyl group and end‐hydroxyl group of R‐PET. FT‐IR spectra testified that the reactions have been happened in the extruding process. A chain extending reaction not only increased the molecular weight of PET and PC, but also can synthesize PET‐g‐PC copolymer to act as a reactive compatilizer. An SEM micrograph shows that a micro‐fiber structure of PET was formed in the blend sample. Copyright © 2007 John Wiley & Sons, Ltd.     

Aging and cold crystallization of melt‐extruded poly(trimethylene terephthalate) films

We analyzed the thermal crystallization, glass‐transition behavior, and mechanical properties of melt‐extruded poly(trimethylene terephthalate) (PTT) films to investigate their physical aging and annealing effects. The physical aging and annealing of PTT films had an influence on the glass‐transition temperature, recrystallization behavior, and mechanical properties. When samples were aged at an ambient temperature, the crystallization temperature decreased largely within 5 h, the heat of crystallization increased, and the breaking stress and breaking elongation increased. The glass‐transition temperature of annealed samples, which was obtained from differential scanning calorimetry and dynamic mechanical measurements, increased with increasing annealing temperature below 80 °C but decreased above that temperature. In addition, the glass‐transition temperature and modulus of annealed samples were largely affected by the annealing time; in particular, they increased sharply within 1 h on annealing at 50 °C. Consequently, the change in the glass‐transition temperature on annealing was ascribed to the fact that the molecular constraint due to recrystallization and the mobility of rigid amorphous PTT chains competed with each other, being dependent on the annealing temperature. The mechanical properties of aged samples were closely related to their cold‐crystallization behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1920–1927, 2001     

Mechanical properties and characterization of slowly cooled isotactic polypropylene/high‐density polyethylene blends

In previous studies, we found that Young's moduli of quenched isotactic polypropylene/high‐density polyethylene (iPP/HDPE) exceeded the upper bound, calculated from the Voigt model, with the moduli of the quenched homopolymers as those of the two components. We suggested that this might be due to crystallization, as the components crystallized at higher temperatures in the blend than on their own. We repeated the same set of measurements, this time on iPP/HDPE blends that were cooled slowly. We also examined crystallization at various rates of cooling with differential scanning calorimetry. At slow cooling rates, the HDPE and iPP components in the blends crystallize at lower temperatures than in the pure homopolymers, suggesting that the presence of one component inhibits rather than promotes the crystallization of the other. Electron microscopy of slowly cooled blends revealed very different interfacial morphologies depending on whether the HDPE or the iPP crystallizes first. Young's moduli of most of the blends lie on the upper bound; however, some blends with co‐continuous morphologies fall well below the lower bound. The mechanical properties are discussed in terms of the interfacial morphology, the crystallization behavior, and the large‐scale phase separation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1384–1392, 2003     

Fiber structure development in high‐speed melt spinning of poly(trimethylene terephthalate) (PTT)—On‐line measurement of birefringence

To investigate the mechanism of fiber structure development for poly(trimethylene terephthalate) (PTT) in high‐speed spinning, the PTT fiber was spun with take‐up speeds from 1 to 8 km/min and simultaneously birefringence and diameter in spin‐line were measured by on‐line measurement system. The orientation‐induced crystallization of PTT fiber started to be developed at 3–4 km/min, where an abrupt decrease in diameter and an increase in birefringence appeared. The birefringence increased up to 4 km/min, decreased suddenly, and then increased gradually. The sudden decrease of birefringence at 4–5 km/min might be caused by an increase of crystalline fraction due to the fact that the intrinsic crystalline birefringence of PTT is over 10 times as low as that of PET. In WAXD images, crystalline diffraction emerged faintly at 3 km/min and distinct diffraction arcs were observed at 4–5 km/min and above. The diffraction intensity increased and the tilting angle also increased with take‐up speed. The long period structure observed in SAXS pattern started to emerge at 6 km/min, and its scattering intensity increased with take‐up speed. The long period structure was ～11–12 nm long. The cold crystallization temperature in DSC thermogram shifted to lower temperature and diminished due to the orientation‐induced crystallization as take‐up speed increased, but the melting temperature hardly increased unlike PBT and PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 847–856, 2008