Melting behavior,isothermal and nonisothermal crystallization kinetics of nylon 1111

The isothermal and nonisothermal crystallization kinetics of nylon 1111 was extensively studied using differential scanning calorimetry (DSC). The equilibrium melting temperature of nylon 1111 was determined to be 188°C. In this article, the Avrami equation was used to describe the isothermal crystallization behavior of nylon 1111. On the basis of the DSC results, the Avrami exponent, n, was determined to be around 3 during the isothermal crystallization process. Nonisothermal crystallization was analyzed using both the Avrami equation as modified by Jeziorny and an equation suggested by Mo. The larger value of the Avrami exponent, n, during the nonisothermal crystallization process indicates that the development of nucleation and crystal growth are more complicated during the nonisothermal crystallization for nylon 1111, and that the nucleation mode might simultaneously include both homogeneous and heterogeneous nucleations. The isothermal and nonisothermal crystallization activation energies of nylon 1111 were determined to be ?132 kJ/mol and ?121 kJ/mol using the Arrhenius equation and the Kissinger method, respectively. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Polylactide/nano‐ and micro‐scale silica composite films. II. Melting behavior and cold crystallization

Nonisothermal crystallization of polylactide (PLA)/silica composites prepared by (i) directly blending the PLA with nanoscale colloidal silica sol and by (ii) a sol–gel process are studied by differential scanning calorimeter (DSC) at various heating rates. Samples quenched from the molten state exhibited two melting endotherms (T_ml and T_mh) due to melt‐recrystallization during the DSC scans. Lower heating rate and the presence of silica particles generate a lower peak intensity ratio of T_ml /T_mh. The nonisothermal crystallization kinetics is analyzed by modified Avrami model, Ozawa model, and Liu‐Mo models. The modified Avrami and Liu‐Mo models successfully described the nonisothermal cold crystallization processes, but Ozawa is inapplicable. The nucleation constant (K_g) is calculated by modified Lauritzen‐Hoffman equation and the activation energy by Augis‐Bennett, Kissinger, and Takhor models. These calculated parameters indicate consistently that the nanoscale silica particles seem to form more heterogeneous nucleation to increase crystallization, but microscale one form hindrance to retard crystallization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization kinetics and morphology of self‐seeded syndiotactic 1,2‐polybutadiene

Subsequent melting behavior after isothermal crystallization at different temperatures from the isotropic melt and nonisothermal crystallization kinetics and morphology of partially melting sPB were carried out by differential scanning calorimetry (DSC), polarized light microscopy (POM), respectively. Triple melting‐endothermic peaks were observed for the polymer first isothermally crystallized at temperatures ranging from 141 to 149°C, respectively, and then followed by cooling at 10°C/min to 70°C. Comparing with the nonisothermal crystallization from the isotropic melt, the nonisothermal crystallization for the partially melting sPB characterized the increased onset crystallization temperature, and the sizes of spherulites became smaller and more uniform. The Tobin, Avrami, Ozawa, and the combination of Avrami and Ozawa equations were applied to describe the kinetics of the nonisothermal process. Both of the Tobin and the Avrami crystallization rate parameters (K_T and K_A, respectively) were found to increase with increase in the cooling rate. The parameter F(T) for the combination of Avrami and Ozawa equations increases with increasing relative crystallinity. The Ziabicki's kinetic crytallizability index G_Z for the partially melting sPB was found to be 3.14. The effective energy barrier Δ? describing the nonisothermal crystallization of partially melting sPB was evaluated by the differential isoconversional method of Friedman and was found to increase with an increase in the relative crystallinity. At the same time, Hoffman‐Lauritzen parameters (U and K_g) are evaluated and analyzed from the nonisothermal crystallization data by the combination of isoconversional approach and Hoffman‐Lauritzen theory. The K_g value obtained from DSC technique was found to be in good agreement with that obtained from POM technique. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1479–1491, 2006     

Melting,crystallization behaviors,and nonisothermal crystallization kinetics of PET/PTT/PBT ternary blends

The melting, crystallization behaviors, and nonisothermal crystallization kinetics of the ternary blends composed of poly(ethylene terephthalate), poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate) (PBT) were studied with differential scanning calorimeter (DSC). PBT content in all ternary blends was settled invariably to be one‐third, which improved the melt‐crystallization temperature of the ternary blends. All of the blend compositions in amorphous state were miscible as evidenced by a single, composition‐dependent glass transition temperature (T_g) observed in DSC curves. DSC melting thermograms of different blends showed different multiple melting and crystallization peaks because of their various polymer contents. During melt‐crystallization process, three components in blends crystallized simultaneously to form mixed crystals or separated crystals depending upon their content ratio. The Avrami equation modified by Jeziorny and the Ozawa theory were employed to describe the nonisothermal crystallization process of two selected ternary blends. The results spoke that the Avrami equation was successful in describing the nonisothermal crystallization process of the ternary blends. The values of the t_1/2 and the parameters Z_c showed that the crystallization rate of the ternary blends with more poly(ethylene terephthalate) content was faster than that with the lesser one at a given cooling rate. The crystal morphology of the five ternary blends investigated by polarized optical microscopy (POM) showed different size and distortional Maltese crosses or light spots when the PTT or poly(ethylene terephthalate) component varied, suggesting that the more the PTT content, the larger crystallites formed in ternary blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide)

The isothermal and nonisothermal crystallization kinetics of a semicrystalline copolyterephthalamide based on poly(decamethylene terephthalamide) (PA‐10T) was studied by differential scanning calorimetry. Several kinetic analyses were used to describe the crystallization process. The commonly used Avrami equation and the one modified by Jeziorny were used, respectively, to describe the primary stage of isothermal and nonisothermal crystallization. The Avrami exponent n was evaluated to be in the range of 2.36–2.67 for isothermal crystallization, and of 3.05–5.34 for nonisothermal crystallization. The Ozawa analysis failed to describe the nonisothermal crystallization behavior, whereas the Mo–Liu equation, a combination equation of Avrami and Ozawa formulas, successfully described the nonisothermal crystallization kinetics. In addition, the value of crystallization rate coefficient under nonisothermal crystallization conditions was calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 819–826, 2004     

Isothermal and nonisothermal melt crystallization kinetics of a novel poly(aryl ether ketone ether ketone ketone) containing a meta‐phenyl linkage

The isothermal and nonisothermal melt crystallization kinetics of a novel poly(aryl ether ketone ether ketone ketone) containing a meta‐phenyl linkage (PEKEKmK) were studied by differential scanning calorimetry. The Avrami equation was used to analyze the isothermal crystallization kinetics of PEKEKmK. The crystallization mechanism did not change within the crystallization temperature range, but the crystallization rate decreased with an increase in the crystallization temperature. The equilibrium melting point, T, was determined to be 327°C according to the Hoffman–Weeks equation. Moreover, the nonisothermal crystallization kinetics of PEKEKmK was also investigated by the Avrami equation as modified by Jeziorny. It was found that the nonisothermal crystallization behavior of PEKEKmK could be described well by this method at various cooling rates, although the parameters n and Z_c did not have the same clear physical meaning as for isothermal crystallization kinetics. The thermal properties and crystallization characteristics of PEKEKmK were compared with those of all‐para PEKEKK(T) and PEKEKK(T/I) with a T/I ratio of 1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4775–4779, 2006     

Crystallization kinetics and melting behavior of poly[(trimethylene terephthalate)‐co‐(29 mol % ethylene terephthalate)] copolyester

The copolyester was characterized as having 71 mol % trimethylene terephthalate units and 29 mol % ethylene terephthalate units in a random sequence according to the NMR spectra. Differential scanning calorimeter (DSC) was used to investigate the isothermal crystallization kinetics in the temperature range (T_c) from 130 to 170°C. The melting behavior after isothermal crystallization was studied using DSC and temperature‐modulated DSC by varying the T_c, the crystallization time, and the heating rate. The DSC thermograms and wide‐angle X‐ray diffraction patterns reveal that the complex melting behavior involves melting‐recrystallization‐remelting and different lamellar crystals. As the T_c increases, the contribution of recrystallization gradually falls and finally disappears. A Hoffman‐Weeks linear plot yields an equilibrium melting temperature of 198.7°C. The kinetic analysis of the growth rates of spherulites and the change in the morphology from regular to banded spherulites indicate that a regime II→III transition occurs at 148°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Isothermal and nonisothermal crystallization kinetics of fully bio‐based polyamides

We studied the crystallization behaviors of bio‐based BDIS polyamides synthesized from the following biomass monomers: 1,4‐butanediamine (BD), 1,10‐decanediamine (DD), itaconic acid (IA), and sebacic acid (SA). Isothermal crystallization, melting behavior, and nonisothermal crystallization of BDIS polyamides were investigated by differential scanning calorimetry (DSC). The Avrami equation was used to describe the isothermal crystallization of BDIS polyamides. The modified Avrami equation, the Ozawa equation, the modified Ozawa equation, and an equation combining the Avrami and Ozawa equations were used to describe the nonisothermal crystallization. The equilibrium melting point temperature of BDIS polyamide was determined to be 163.0°C. The Avrami exponent n was found to be in the range of 2.21–2.79 for isothermal crystallization and 4.10–5.52 for nonisothermal crystallization. POLYM. ENG. SCI., 56:829–836, 2016. © 2016 Society of Plastics Engineers     

Nonisothermal and isothermal crystallization kinetics of nylon‐12

The isothermal and nonisothermal crystallization behavior of Nylon 12 was investigated using differential scanning calorimetry (DSC). An Avrami analysis was used to study the isothermal crystallization kinetics of Nylon 12, the Avrami exponent (n) determined and its relevance to crystal growth discussed and an activation energy for the process evaluated using an Arrhenius type expression. The Lauritzen and Hoffman analysis was used to examine the spherulitic growth process of the primary crystallization stage of Nylon 12. The surface‐free energy and work of chain folding were calculated using a procedure reported by Hoffmann and the work of chain folding per molecular fold (σ) and chain stiffness of Nylon 12 (q) was calculated and compared to values reported for Nylons 6,6 and 11. The Jeziorny modification of the Avrami analysis, Cazé and Chuah average Avrami parameter methods and Ozawa equation were used in an attempt to model the nonisothermal crystallization kinetics of Nylon 12. A combined Avrami and Ozawa treatment, described by Liu, was used to more accurately model the nonisothermal crystallization kinetics of Nylon 12. The activation energy for nonisothermal crystallization processes was determined using the Kissinger method for Nylon 12 and compared with values reported previously for Nylon 6,6 and Nylon 11. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization kinetics of poly (L‐lactic acid)/montmorillonite nanocomposites under isothermal crystallization condition

Poly(L ‐lactic acid)/o‐MMT nanocomposites, incorporating various amounts of organically modified montmorillonite (o‐MMT; 0–10 wt %), were prepared by solution intercalation. The montmorillonite (MMT) was organically modified with dilauryl dimethyl ammonium bromide (DDAB) by ion exchange. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) reveal that the o‐MMT was exfoliated in a poly(L ‐lactic acid), (PLLA) matrix. A series of the test specimens were prepared and subjected to isothermal crystallization at various temperatures (T₁–T₅). The DSC plots revealed that the PLLA/o‐MMT nanocomposites that were prepared under nonisothermal conditions exhibited an obvious crystallization peak and recrystallization, but neat PLLA exhibited neither. The PLLA/o‐MMT nanocomposites (2–10 wt %) yielded two endothermic peaks only under isothermal conditions at low temperature (T₁), and the intensity of Tm₂ (the higher melting point) was proportional to the o‐MMT content (at around 171°C). The melting point of the test samples increased with the isothermal crystallization temperature. In the Avrami equation, the constant of the crystallization rate (k) was inversely proportional to the isothermal crystallization temperature and increased with the o‐MMT content, especially at low temperature (T₁). The Avrami exponent (n) of the PLLA/o‐MMT nanocomposites (4–10 wt %) was 2.61–3.56 higher than that of neat PLLA, 2.10–2.56, revealing that crystallization occurred in three dimensions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystallization kinetics,melting behavior,and morphologies of poly(butylene succinate) and poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyester

This article investigated the crystallization kinetics, melting behavior, and morphologies of poly(butylene succinate)(PBS) and its segmented copolyester poly(butylene succinate)‐block‐poly(propylene glycol)(PBSP) by means of differential scanning calorimetry, polarized light microscopy, and wide angle X‐ray diffraction. Avrami equation was used to describe the isothermal crystallization kinetics. For nonisothermal crystallization studies, the Avrami equation modified by Jeziorny, and the model combining Avrami equation and Ozawa equation were employed. The results showed that the introduction of poly(propylene glycol) soft segment led to suppression of crystallization of PBS hard segment. The melting behavior of the isothermally and nonisothermally crystallized samples was also studied. Results showed that the isothermally crystallized samples exhibited two melting endotherms, whereas only one melting endotherm was shown after nonisothermal crystallization. The spherulitic morphology of PBSP and wide angle X‐ray diffraction showed that the polyether segments were excluded from the crystals and resided in between crystalline PBS lamellae and mixed with amorphous PBS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Crystallization behavior of poly(lactide)/poly(β‐hydroxybutyrate)/talc composites

The morphology and miscibility of commercial poly(lactide) (PLA)/poly(β‐hydroxybutyrate) (PHB, from 5 to 20 wt %) blends prepared by melt extrusion method, were investigated using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) observations. The results show that for all the studied blend contents, PLA/PHB blends are immiscible. The effects of PHB and talc on the nonisothermal cold crystallization kinetics of PLA were examined using a differential scanning calorimetry (DSC) at different heating rates. PHB acted as a nucleating agent on PLA and the addition of talc to the blend yielded further improvement, since significant increase in the enthalpy peak was observed for samples containing 10 wt % PHB and talc (from 0.5 to 5 phr). The crystallization kinetics were then examined using the Avrami–Jeziorny and Liu–Mo approach. The simultaneous presence of PHB and talc induced a decrease of the crystallization half time. The evolution of activation energies determined with Kissinger's equation suggests that blending with PHB and incorporating talc promote nonisothermal cold crystallization of PLA. The synergistic nucleating effect of PHB and talc was also observed on isothermal crystallization of PLA from the melt. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization kinetics and melting behaviour of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)

Isothermal and non‐isothermal crystallization kinetics of microbial poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(3HB‐3HHx)] was investigated by differential scanning calorimetry (DSC) and ¹³C solid‐state nuclear magnetic resonance (NMR). Avrami analysis was performed to obtain the kinetic parameters of primary crystallization. The results showed that the Avrami equation was suitable for describing the isothermal and non‐isothermal crystallization processes of P(3HB‐3HHx). The equilibrium melting temperature of P(3HB‐3HHx) and its nucleation constant of crystal growth kinetics, which were obtained by using the Hoffman–Weeks equation and the Lauritzen–Hoffmann model, were, respectively, 121.8 °C and 2.87 × 10⁵ K² when using the empirical ‘universal’ values of U* = 1500 cal mol^?1. During the heating process, the melting behaviour of P(3HB‐3HHx) for both isothermal and non‐isothermal crystallization showed multiple melting peaks, which was the result of melting recrystallization. The lower melting peak resulted from the melting of crystals formed during the corresponding crystallization process, while the higher melting peak resulted from the recrystallization that took place during the heating process. Copyright © 2005 Society of Chemical Industry     

Crystallization kinetics of novel poly(aryl ether ketone) copolymers containing 2,7‐naphthalene moieties

To increase the glass transition temperature (T_g) of poly(aryl ether ketone), and to decrease the melting temperature (T_m) and temperature of processing, a series of novel poly(aryl ether ketone)s with different contents of 2,7‐naphthalene moieties (PANEK) was synthesized. We focused on the influence of the naphthalene contents to the copolymer's crystallization. The crystallization kinetics of the copolymers was studied isothermally and nonisothermally by differential scanning calorimetry. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the crystallization. The study results of the crystallization of PANEK at cooling/heating rates ranging from 5 to 60°C/min under nonisothermal conditions are also reported. Both the Avrami equation and the modified Avrami–Ozawa equation were used to describe the nonisothermal crystallization kinetics of PANEK. The results show that the increase in the crystallization temperature and the content of 2,7‐naphthalene moieties will make the crystallization rate decrease, while the nucleation mechanism and the crystal growth of PANEK are not influenced by the increasing of the content of 2,7‐naphthalene moieties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2527–2536, 2006     

Crystallization behavior of poly(ether ether ketone ketone)

The melting behavior of semicrystalline poly(ether ether ketone ketone) (PEEKK) has been studied by differential scanning calorimetry (DSC). When PEEKK is annealed from the amorphous state, it usually shows two melting peaks. The upper melting peaks arise first, and the lower melting peaks are developed later. The upper melting peaks shown in the DSC thermogram are the combination (addition) of three parts: initial crystal formed before scanning; reorganization; and melting-recrystallization of lower melting peaks in the DSC scanning period. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the isothermal crystallization; the Avrami constant, n, is about 2 for PEEKK from the melt and 1.5 for PEEKK from the glass state. According to the Lauritzen-Hoffman equation, the kinetic parameter of PEEKK from the melt is 851.5 K; the crystallization kinetic parameter of PEEKK is higher than that of PEEK, and suggests the crystallizability of PEEKK is less than that of PEEK. The study of crystallization on PEEKK under nonisothermal conditions is also reported for cooling rates from 2.5°C/min to 40°C/min, and the nonisothermal condition was studied by Mandelkern analysis. The results show the nonisothermal crystallization is different from the isothermal crystallization. © 1996 John Wiley & Sons, Inc.     

Nonisothermal crystallization kinetics of linear bimodal–polyethylene (LBPE) and LBPE/low‐density polyethylene blends

Nonisothermal crystallization kinetics of linear bimodal–polyethylene (LBPE) and the blends of LBPE/low‐density polyethylene (LDPE) were studied using DSC at various scanning rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the nonisothermal crystallization process of LBPE and LBPE/LDPE blends. The theory of Ozawa was also used to analyze the LBPE DSC data. Kinetic parameters such as, for example, the Avrami exponent (n), the kinetic crystallization rate constant (Z_c), the crystallization peak temperature (T_p), and the half‐time of crystallization (t_1/2) were determined at various scanning rates. The appearance of double melting peaks and double crystallization peaks in the heating and cooling DSC curves of LBPE/LDPE blends indicated that LBPE and LDPE could crystallize, respectively. As a result of these studies, the Z_c of LBPE increases with the increase of cooling rates and the T_p of LBPE for LBPE/LDPE blends first increases with increasing LBPE content in the blends and reaches its maximum, then decreases as the LBPE content further increases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2431–2437, 2003     

Crystallization and melting behavior of iPP studied by DSC

This article is a part of a study of model and bulk composites, based on isotactic polypropylene (i-PP) and glass (or carbon) fibers, produced from knitted textile preforms of hybrid yarns. First, we report the results on crystallization and fusion of textile-grade i-PP, used for the processing of hybrid yarns and the corresponding knitted fabrics. The kinetics of the crystallization process, in the dynamic and isothermal regime, was followed by DSC, and the results were analyzed by Avrami, Ozawa, and Harnisch-Muschik methods. Isothermal crystallization of i-PP was carried out at 388–400 K, and values for the Avrami exponent ranging from 1.93 to 4.39 were determined. The equilibrium melting temperature was determined by the Hoffman-Weeks method, and γ = 2.54 was found. Double melting peaks were observed both when the crystallization was performed at lower temperatures (isothermal regime) and at higher cooling rates (nonisothermal regime). A single melting peak appeared upon melting following isothermal crystallization at 400 K. The nonisothermal kinetics data showed that the peak crystallization temperature changes from 377 to 386 K as the cooling rate decreases from 20 to 3 K/min. Applying the Ozawa method, a value of the exponent n = 2.33 was determined, which is in agreement with the results for isothermal crystallization at 391–400 K. The Harnisch-Muschik approach was also applied to compare the results for n, and a similar trend in the results of isothermal and nonisothermal crystallization was found, due to the predominant homogeneous mechanism of nucleation at lower cooling rates (lower isothermal T_c) in spite of being heterogeneous at higher cooling rates (higher isothermal T_c). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 395–404, 1998     

PE/PE‐g‐MAH/Org‐MMT nanocomposites. II. Nonisothermal crystallization kinetics

The nonisothermal crystallization kinetics of high‐density polyethylene (HDPE) and polyethylene (PE)/PE‐grafted maleic anhydride (PE‐g‐MAH)/organic‐montmorillonite (Org‐MMT) nanocomposite were investigated by differential scanning calorimetry (DSC) at various cooling rates. Avrami analysis modified by Jeziorny, Ozawa analysis, and a method developed by Liu well described the nonisothermal crystallization process of these samples. The difference in the exponent n, m, and a between HDPE and the nanocomposite indicated that nucleation mechanism and dimension of spherulite growth of the nanocomposite were different from that of HDPE to some extent. The values of half‐time (t_1/2), K(T), and F(T) showed that the crystallization rate increased with the increase of cooling rates for HDPE and composite, but the crystallization rate of composite was faster than that of HDPE at a given cooling rate. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. It was 223.7 kJ/mol for composite, which was much smaller than that for HDPE (304.6 kJ/mol). Overall, the results indicated that the addition of Org‐MMT and PE‐g‐MAH could accelerate the overall nonisothermal crystallization process of PE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3054–3059, 2004     

Crystallization behavior of polytetrafluoroethylene (PTFE)

For some polymers such as PTFE, the crystallization is so rapid that it is difficult to observe isothermal crystallization by differential scanning calorimetry (DSC). In this investigation, first, isothermal crystallization kinetics of PTFE was followed by DSC and the results were analyzed by the Avrami method, which showed that PTFE crystallizes one‐dimensionally from preexisting nuclei, presumably impurities. Furthermore, the crystallization activation energy, the equilibrium melting point, and the nucleation rate parameter K_g were calculated in the isothermal crystallization. Second, nonisothermal crystallization was also studied and the result was in accordance with the results of isothermal crystallization. Then, the Kissinger method was used to investigate the activation energy of PTFE in the nonisothermal crystallization. Third, the effect of glass fiber (used as filling) was investigated on crystallization of PTFE matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 990–996, 2002     

Effect of molecular weight on crystallization and melting of poly(trimethylene terephthalate). 1: Isothermal and dynamic crystallization

The crystallization behavior of poly(trimethylene terephthalate) as a function of molecular weight was investigated under isothermal and dynamic cooling conditions using a differential scanning calorimeter (DSC) and polarized light optical microscopy (POM). THe overall rate of bulk crystallization increased with molecular weight. An Avrami analysis of the isothermal crystallization kinetics indicated that the crystallization rate constant increased with increasing molecular weight. The Avrami exponent, n, approached 2 and was nearly independent of both molecular weight and temperature. The modified Avrami analysis developed by Jeziorny and Ozawa was applied to the dynamic crystallization data. At the same cooling rate, higher molecular weight resulted in a narrower crystallization peak, higher onset crystallization temperature, and larger rate constant (Z_t)^1/n. Higher molecular weight resulted in larger cooling function of dynamic crystallization K(T) and lower Ozawa exponent m. For dynamic crystallization, the average value of the Avrami exponent varied from 3.4 to 3.8 and the average value of the Ozawa exponent changed from 2.3 to 2.6 as the number‐average molecular weight changed from 13,000 to 67,000. Morphology studies indicated that both the isothermal crystallization and the dynamic crystallization of PTT from the melt were thermal nucleation processes, and for a fixed temperature between 190°C and 210°C, the nucleation density increased with increasing the molecular weight.