Isothermal and nonisothermal crystallization kinetics of nylon-11

Analysis of the isothermal, and nonisothermal crystallization kinetics of Nylon-11 is carried out using differential scanning calorimetry. The Avrami equation and that modified by Jeziorny can describe the primary stage of isothermal and nonisothermal crystallization of Nylon-11. In the isothermal crystallization process, the mechanism of spherulitic nucleation and growth are discussed; the lateral and folding surface free energies determined from the Lauritzen–Hoffman equation are ς = 10.68 erg/cm² and ς_e = 110.62 erg/cm²; and the work of chain folding q = 7.61 Kcal/mol. In the nonisothermal crystallization process, Ozawa analysis failed to describe the crystallization behavior of Nylon-11. Combining the Avrami and Ozawa equations, we obtain a new and convenient method to analyze the nonisothermal crystallization kinetics of Nylon-11; in the meantime, the activation energies are determined to be −394.56 and 328.37 KJ/mol in isothermal and nonisothermal crystallization process from the Arrhonius form and the Kissinger method. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2371–2380, 1998     

Crystallization behavior of a novel poly(aryl ether ketone): PEDEKmK

Isothermal melt and cold crystallization kinetics of PEDEKmK linked by meta-phenyl and biphenyl were investigated by differential scanning calorimetry in two temperature regions. Avrami analysis is used to describe the primary stages of the melt and cold crystallization, with exponent n = 2 and n = 4, respectively. The activation energies are − 118 kJ/mol and 510 kJ/mol for crystallization from the melt and the glassy states, respectively. The equilibrium melting point T⁰_m is estimated to be 309°C by using the Hoffman-Weeks approach, which compares favorably with determination from the Thomson-Gibbs method. The lateral and end surface free energies derived from the Lauritzen-Hoffman spherulitic growth rate equation are σ = 8.45 erg/cm² and σ_e = 45.17 erg/cm², respectively. The work of chain folding q is determined as 3.06 kcal/mol. These observed crystallization characteristics of PEDEKmK are compared with those of the other members of poly(aryl ether ketone) family. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1451–1461, 1997     

Effect of copolymerization on crystallization kinetics of semicrystalline polyimides

Isothermal melt crystallization kinetics and nonisothermal cold crystallization kinetics of co‐PI based on 3, 3′, 4, 4′‐biphenyltetracarboxylic dianhydride (s‐BPDA)/1, 3‐bis‐(4‐aminophenoxy) benzene (TPER)/4, 4′‐oxydianiline(4, 4′‐ODA), and TPER PI (s‐BPDA/TPER) have been investigated. Avrami equation was used to analyze isothermal melt crystallization progress of TPER PI and co‐PI, primary crystallization processes was found to be changed as the introduction of 4, 4′‐ODA. Total activation energy ΔE for TPER PI and co‐PI were found to be ?404 and ?86 kJ mol^?1 by Arrhenius equation. Jeziorny's analysis, Ozawa's analysis, and Mo's approach were used to investigate nonisothermal cold crystallization progress of TPER PI and co‐PI. Activation energy ΔE_non for TPER PI and co‐PI were found to be 247 and 193 kJ mol^?1 by Kissinger equation. The result indicated that co‐PI exhibited lower crystallization rate than TPER PI when isothermally crystallized from melt, but higher crystallization rate under cold nonisothermal crystallization progress. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cold‐crystallization kinetics of syndiotactic polystyrene

The kinetics of the isothermal and nonisothermal cold crystallization of syndiotactic polystyrene (s‐PS) were characterized with differential scanning calorimetry. A Johnson–Mehl–Avrami analysis of the isothermal experiments indicated that the cold crystallization of s‐PS at a constant temperature followed a diffusion‐controlled growth mode with a decreasing nucleation rate. Furthermore, the slow nucleation rate was the controlling step of the entire kinetic process. For nonisothermal cold‐crystallization kinetics, we used a simple model based on a combination of the well‐known Avrami and Ozawa models. The analysis revealed that, unlike for melt crystallization, the Avrami and Ozawa exponents were not equal. The activation energies for the isothermal and nonisothermal cold crystallizations of s‐PS were 792.0 and 148.62 kJ mol^?1, respectively, indicating that the smaller motion units in cold crystallization had a weaker temperature dependence than those in melt crystallization. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3464–3470, 2003     

Isothermal and nonisothermal crystallization kinetics of syndiotactic polystyrene/clay nanocomposites

Differential scanning calorimeter (DSC) and X‐ray diffraction methods were used to investigate the isothermal and nonisothermal crystallization behavior and crystalline structure of syndiotactic polystyrene (sPS)/clay nanocomposites. The sPS/clay nanocomposites were prepared by mixing the sPS polymer solution with the organically modified montmorillonite. DSC isothermal results revealed that introducing 5 wt% of clay into the sPS structure causes strongly heterogeneous nucleation, inducing a change of the crystal growth process from mixed three‐dimensional and two‐dimensional crystal growth to two‐dimensional spherulitic growth. The activation energy of sPS drastically decreases with the presence of 0.5 wt% clay and then increases with increasing clay content. The result indicates that the addition of clay into sPS induces the heterogeneous nucleation (a lower ΔE) at lower clay content and then reduces the transportation ability of polymer chains during crystallization processes at higher clay content (a higher ΔE). We studied the non‐isothermal melt‐crystallization kinetics and melting behavior of sPS/clay nanocomposites at various cooling rates. The correlation among crystallization kinetics, melting behavior and crystalline structure of sPS/clay nanocomposites is discussed. Polym. Eng. Sci. 44:2288–2297, 2004. © 2004 Society of Plastics Engineers.     

Effect of lignin particles as a nucleating agent on crystallization of poly(3‐hydroxybutyrate)

The effect of lignin fine powder, as a new kind of nucleating agent, on the crystallization process of poly(3‐hydroxybutyrate) (PHB) was studied. The kinetics of both isothermal and nonisothermal crystallization processes from the melt for both pure PHB and PHB/lignin blend was studied by means of differential scanning calorimetry. Lignin shortened the crystallization half‐time t_1/2 for isothermal crystallization. The activation energy ΔE for PHB/lignin and pure PHB in the isothermal crystallization process was ?237.40 and ?131.22 kJ/mol, respectively, clearly indicating that the crystallization of the PHB/lignin blend was more favorable than that of pure PHB from a thermodynamic perspective. At the same time, according to polarized optical microscopy, the rate of spherulitic growth from the melt increased with the addition of lignin, which is ascribed to the reduction of surface fold energy σ_e, that is, σ_e is 59.2 × 10^?3 and 41.6 × 10^?3 J m^?2 for pure PHB and PHB/lignin, respectively. Polarized optical microscopy also showed that the spherulites found in PHB with lignin were smaller in size and greater in number than those found in pure PHB. The wide‐angle X‐ray diffraction indicated that an addition of lignin caused no change in the crystal structure and degree of crystallinity. These results indicated that lignin is a good nucleating agent for the crystallization of PHB. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2466–2474, 2004     

Structure,crystallization, and properties of poly(aryl ether ether ketone ketone)s containing meta-phenyl links and their copolymers

Poly(aryl ether ether ketone ketone)s (PEEKK) containing meta-phenyl links and their series of copolymers were synthesized and investigated by both X-ray and differential scanning calorimetry (DSC) methods. Results showed that the heat properties of this kind of copolymer depended greatly on the content of meta-phenyl links in the copolymer system, in which occurred the lowest melting point. Results from X-rays showed that PEEKK containing meta-phenyl links had no (111) crystal face diffraction. These proved that meta-phenyl links had introduced asymmetrical factors, which had produced poor crystal structure and difficulty in crystallization. Even so, the modification of PEEKK by introducing the meta-phenyl links improved the polymer composite performances, e.g., the copolymer M₂, which kept performances close to PEEKK but better than PEEK. DSC results of M₂ showed that its Avrami number (n) was 1.5 and its crystal grew fibrously from isothermal crystallization of the melting state, while for the nonisothermal crystallization from the melting state, n was 4.4 to the spherical crystal growth, and the activation energy (ΔE) of crystallization was 184 kJ/mol, which was less than the ΔE of 296 kJ/mol for PEEKK crystallized from the nonisothermal melting state. When M₂ was isothermally crystallized from the rubber state, its n was 2 to the disklike crystal growth, while its n was 4.6 to the spherulitic crystal growth for the nonisothermal crystallization state of melting. The isothermal crystallization process was different from the nonisothermal process in the crystal nucleation and growth for M₂. © 1996 John Wiley & Sons, Inc.     

Kinetics of isothermal and nonisothermal crystallization of nylon 1313

The crystallization process of a new polyamide, nylon 1313, from the melt has been thoroughly investigated under isothermal and nonisothermal conditions. During isothermal crystallization, relative crystallinity develops in accordance with the Avrami equation with the exponent n ≈ 2 based on DSC analysis. Under nonisothermal conditions, several different analysis methods were used to elucidate the crystallization process. The Avrami exponent n is greater in the isothermal crystallization process, indicating that the mode of nucleation and the growth of the nonisothermal crystallization for nylon 1313 are more complicated, and that the nucleation mode might include both homogeneous and heterogeneous nucleation simultaneously. The calculated activation energy is 214.25 kJ/mol for isothermal crystallization by Arrhenius form and 135.1 kJ/mol for nonisothermal crystallization by Kissinger method, respectively. In addition, the crystallization ability of nylon 1313 was assessed by using the kinetic crystallizability parameters G. Based on this parameter, the crystallizability of many different polymers was compared theoretically. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1415–1422, 2007     

Non‐isothermal crystallization and multiple melting behavior of syndiotactic polystyrene—pre‐melting temperature effects

This work investigated how pre‐melting temperature (T_max) and cooling rate (C) affected the non‐isothermal melt crystallization, melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) techniques. Experimental results indicated that raising T_max or C decreased the crystallization peak temperature (T_p) and crystallization initiating temperature (T_i). The crystallization kinetics was analyzed through the Ozawa equation. Although the Ozawa exponent n and cooling function K(T) were determined for T_max = 340°C and T_max = 315°C specimens, for T_max = 290°C specimens, the Ozawa equation was not applicable. Activation energies for the non‐isothermal crystallization processes of different T_max specimens were estimated to be approximately 418 kJ/mol. As T_max was raised the nucleation rate of sPS became slower. The multiple melting peaks were associated with different polymorphs as well as recrystallized crystals that formed during heating scans. The percentage content of α polymorph formed in the crystals under various crystallization conditions was estimated through WAXD experiments.     

Syntheses and characterization of polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole and its sorption behavior for Pd(II), Pt(IV), and Au(III)

A type of chelating resin crosslinking polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT), containing sulfur and nitrogen atoms, was prepared. The structure of PS‐BMT was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). Adsorption of Pd(II), Pt(IV), and Au(III) was investigated. The capacity of PS‐BMT to adsorb Pd(II) and Pt(IV) was 0.190 and 0.033 mmol/g, respectively. The adsorption dynamics of Pd(II) showed that adsorption was controlled by liquid film diffusion and that the apparent activation energy, E_a, was 32.67 kJ/mol. The Langmuir model was better than the Freundlich model in describing the isothermal process of Pd(II), and the ΔG, ΔH, and ΔS values calculated were ?0.33 kJ/mol, 26.29 kJ/mol, and 87.95 J mol^?1 K^?1, respectively. The mechanisms of adsorption of Pd(II), Pt(IV), and Au(III) were confirmed by XPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 631–637, 2006     

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     

Crystallization behavior,morphology, and mechanical properties of poly(lactic acid)/tributyl citrate/treated calcium carbonate composites

In this article, poly(lactic acid) (PLA) composites containing titanate coupling agent treated calcium carbonate (T‐CaCO₃) and tributyl citrate (TBC) were prepared via melt blending. The crystallization, morphology, mechanical properties, and nonisothermal cold crystallization kinetics of PLA composites were studied by means of differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), polarized light microscopy (PLM), scanning electron microscopy (SEM), and mechanical tests, respectively. The results show that TBC promotes crystallization of PLA. Both T‐CaCO₃ and TBC significantly decrease the spherulitic size, but the crystal structure of PLA is not changed. A synergistic toughening effect is obtained by the combination of T‐CaCO₃ and TBC. The nonisothermal cold crystallization kinetics of PLA composites is well described by Mo's method. The activation energies (ΔE) of nonisothermal cold crystallization were calculated by Kissinger and Takhor methods, respectively. It is found that the addition of T‐CaCO₃ and TBC increases ΔE, but it also increases the cold crystallization rate. POLYM. COMPOS., 35:1570–1582, 2014. © 2013 Society of Plastics Engineers     

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     

Characterization and properties of sPS/PET/SsPS‐K engineering plastic alloys

The compatibility, crystallization behavior, and mechanical properties of syndiotactic polystyrene (sPS)/polyester (PET)/potassium salt of sulfonated syndiotactic polystyrene (SsPS‐K) were investigated. DMA results showed that all the alloys showed one T_g and the half‐peak width of the sPS/PET/SsPS‐K alloys became narrower compared with that of sPS/PET alloys, which decreased with an increasing content of the SsPS‐K ionomer. The results of DSC showed that the T_m of sPS and PET of the alloys was similar to those of the pure materials and did not change with the content of the SsPS‐K ionomer, while the initial crystallization temperature (T₀) and crystallization temperature at peak (T_p) increased. The crystallization velocity of PET increased with an increasing content of SsPS‐K. The TMA results showed that the alloys could retain the perfect heat proof property of sPS. SEM micrographs showed that the addition of SsPS‐K could reduce the PET domain dimension and enhance the adhesion between the PET domains and the matrix. With an increasing content of SsPS‐K, the PET domain dimension was reduced continuously and dispersed more evenly. The ternary alloys had better mechanical properties and significantly higher unnotched Izod impact strength than those of the alloys without SsPS‐K. When the weight ratio of sPS/PET/SsPS‐K was 85/15/4, the impact strength reached a maximum of 11.5 kJ/m², which was about three times that of pure sPS, and still had a higher tensile strength, flexural strength, and storage modulus, which were 38.8, 54.2, and 1.55 × 10⁴ MPa, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 656–661, 2002     

Morphology and melt crystallization of poly(L‐lactide) obtained by ring opening polymerization of L‐lactide with zinc catalyst

The morphology and melt crystallization of zinc catalyzed poly(L ‐lactide) (PLLA) were investigated by using differential scanning calorimetry (DSC), polarized optical microscopy, and scanning electron microscopy. Isothermal melt crystallization performed at 95–135°C showed that the morphology depends on the degree of supercooling, as illustrated by crystallite perfection and lamellar thickening behaviors. Double melting peak was observed on DSC thermograms and attributed to the melt‐recrystallization mechanism, small and imperfect crystals becoming gradually more stable ones. Circumferential and hexagonal cracks were detected in PLLA spherulites, which were formed during melt‐crystallization at 135°C and quenching in liquid nitrogen. Rhythmic growth and thermal shrinkage are suggested to be the two main factors accounting for the formation of periodic cracks. Spherulite growth rates of PLLA were evaluated by using combined isothermal and nonisothermal procedures, and were analyzed by the secondary nucleation theory. The maximum growth rate reached 9.1 μm/min at 130°C. The temperature range investigated (120–155°C) belongs to the Regime II of crystallization. The value of U* was found to be 1890 cal/mol, instead of 1500 cal/mol commonly used in literature, and K_g and σ were estimated to be 3.03 × 10⁵ K² and 1.537 × 10^?4 J/m², respectively. As a result, no distinct difference between PLLA catalyzed by zinc metal and those prepared with stannous octoate catalyst exists in this work. POLYM. ENG. SCI., 46:1583–1589, 2006. © 2006 Society of Plastics Engineers.     

Synthesis and characterization of polystyrene‐supported glucosamine resin and its adsorption behavior for Au(III)

A novel chelating resin, crosslinking polystyrene‐supported glucosamine (PS‐GA), was prepared and its structure was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy. The adsorption properties of PS‐GA for Au(III) were investigated. PS‐GA resin possessed excellent enriching property to Au(III) ions and adsorption proportion E% could reach to about 90 shortly after 3 h. The adsorption dynamics of Au(III) showed that the adsorption was controlled by liquid film diffusion and the apparent activation energy E_a was 12.91 kJ mol^?1. Both Langmuir model and Freundlich model could describe the isothermal process of Au(III), and ΔG, ΔH, ΔS values were calculated. The mechanism of adsorption for Au(III) was confirmed by FTIR, SEM, and XPS. The results showed that redox reaction occurred and both coordination and ion‐exchange existed simultaneously in the adsorption. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4581–4586, 2006     

A comparison of induction time and crystallization rate for syndiotactic polystyrene

One objective of this study was to measure the crystallization parameters for syndiotactic polystyrene (M_W = 244,000) to support a computer simulation of this material in an injection molding application. A second objective was to introduce a new crystallization rate equation that adequately predicts crystallization rates over a broader temperature range than the Hoffman‐Lauritzen equation. A third objective was to establish a new clearly defined method for determining the true induction time of a semicrystalline polymer as a function of temperature. The new crystallization rate equation introduced in this study has been formulated to give appropriate crystallization rate constants for all the temperatures currently usable with the Hoffman‐Lauritzen equation. In addition, this new equation also predicts appropriate crystallization rate constants outside the range of the Hoffman‐Lauritzen equation from temperatures significantly below the glass transition temperature, T_g, to temperatures significantly above the melting point, T_m. Interestingly, the isolation of the true isothermal induction times from apparent induction times in this study nicely mirrored the isothermal crystallization rates at each specific temperature. Both the true induction time and the crystallization rate curves were found to be similarly unsymmetrical as a function of temperature. Also, the temperature at the minimum induction time and the temperature at the peak crystallization rate determined from nonisothermal crystallization rate measurements were found to be nearly identical. Consequently, the results from this study strongly suggest that there is a significant and potentially very useful relationship between induction time analysis and crystallization rate kinetics.     

The morphology of poly(aryl-ether-ether-ketone)

The morphology and related properties are described for the aromatic thermoplastic poly(aryl-ether-ether-ketone) (PEEK) [C₆H₄OC₆H₄OC₆H₄CO]_n. Topics covered include crystallinity, crystallization and melting behaviour, Iamellar thickness and spherulitic structure. The data are used to derive the following material parameters $\text{T1}{}_{\mathrm{<mtext>m</mtext>}}\text{= 395°}\text{C}$, σ_e = 49 erg cm^?2, σ_s = 38 erg cm^? and ΔH_F = 130 kJ kg^?1. PEEK is closely analogous to poly(ethylene terephthalate) in its crystallization behaviour except that the main transitions occur about 75°C higher.     

Pre‐melting temperature effect on the isothermal melt crystallization and multiple melting behavior of syndiotactic polystyrene

This work examined how pre‐melting temperature (T_max) affects the isothermal melt crystallization kinetics, the resulting melting behavior and crystal structure of syndiotactic polystyrene (sPS) by using differential scanning calorimetry (DSC), polarized light microscopy (PLM) and the wide angle X‐ray diffraction (WAXD) technique. Experimental results indicated that raising T_max decreased the nucleation rate and the crystal growth rate of sPS. The Avrami equation was also used to analyze the overall crystallization kinetics. The Avrami exponent n and rate constant K were determined for different T_max specimens at various crystallization temperatures (T_c's). Our results indicated that the nucleation type of sPS is T_max and T_c dependent as well. Evaluation of the activation energy for the isothermal crystallization processes revealed that it increases from 375 kJmol^?1 to 485 kjmol ^?1 with an increase of T_max. From the melting behavior study, we believe that the T_max and T_c‐dependent multiple melting peaks are associated with different polymorphs as well as recrystallized crystals formed during heating scans. Moreover, the percentage content of α form in the crystals formed under different crystallization conditions was estimated through WAXD experiments.