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     

Studies of cyclic and linear poly(dimethylsiloxanes): 19. Glass transition temperatures and crystallization behaviour

Differential scanning calorimetry (d.s.c.) was used to investigate the thermal behaviour of cyclic and linear poly(dimethylsiloxanes) over the temperature range 103–298 K. Fractions of the polymers studied had number-average molar masses in the range 160 < M_n < 25 500 g mol^?1 and heterogeneity indices $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{M}{}_{\mathrm{<mtext>n</mtext>}}\text{< 1.1}$ in most cases. D.s.c. was applied to measure the glass transition temperatures T_g cold crystallization temperatures T_c and polymer crystalline melting temperatures T_m of the oligomer and polymer fractions. Cyclic siloxanes [(CH₃)₂SiO]_x with number-average numbers of skeletal bonds n_n in the range 24 ≦ n_n ≦ 79 and linear siloxanes (CH₃)SiO[(CH₃)₂SiO]_ySi(CH₃)₃ with n_n in the range 10 ≦ n_n ≦ 40 were found not to crystallize. The T_g values of the linear siloxanes were found to be in agreement with values in the literature and they increased with increasing M_n. By contrast, the T_g values of the cyclics were found to decrease with increasing M_n.     

Properties and crystallization kinetics of poly(ether ether ketone)‐co‐poly(ether ether ketone ketone) block copolymers

A series of block copolymers composed of poly(ether ether ketone) (PEEK) and poly(ether ether ketone ketone) (PEEKK) components were prepared from their corresponding oligomers via a nucleophlilic aromatic substitution reaction. Various properties of the copolymers were investigated with differential scanning calorimetry (DSC) and a tensile testing machine. The results show that the copolymers exhibited no phase separation and that the relationship between the glass‐transition temperature (T_g) and the compositions of the copolymers approximately followed the formula T_g = T_g1X₁ + T_g2X₂, where T_g1 and T_g2 are the glass‐transition‐temperature values of PEEK and PEEKK, respectively, and X₁ and X₂ are the corresponding molar fractions of the PEEK and PEEKK segments in the copolymers, respectively. These copolymers showed good tensile properties. The crystallization kinetics of the copolymers were studied. The Avrami equation was used to describe the isothermal crystallization process. The nonisothermal crystallization was described by modified Avrami analysis by Jeziorny and by a combination of the Avrami and Ozawa equations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1652–1658, 2005     

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     

Effect of 1,3,5‐trialkyl‐benzenetricarboxylamide on the crystallization of poly(lactic acid)

A series of 1,3,5‐trialkyl‐benzenetricarboxylamides (BTA‐Rs) with different side‐chain lengths of n‐alkyl are synthesized to use as nucleating agents of poly (lactic acid) (PLA). Crystallization rate of PLA is detailed discussed in nonisothermal melt‐crystallization with addition of the synthesized nucleating agents. Among these BTA‐Rs, BTA‐n‐butyl (BTA‐nBu) shows the most excellent nucleation ability for PLA. The influences of BTA‐nBu on the nonisothermal melt‐crystallization and cold‐crystallization from the glassy state, isothermal crystallization, crystalline structure, and spherulite morphology of PLA are investigated. It is found that 0.8 wt % is the optimal weight fraction of BTA‐nBu to improve the crystallization of PLA. In the case of isothermal melt‐crystallization from melt, the addition of BTA‐nBu shortens the crystallization half‐time and speeds up the crystallization rate of PLA with no discernible effect on the crystalline structure. Besides, BTA‐nBu nucleated PLA exhibits smaller spherulites size and larger nucleation density than that of pure PLA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1328‐1336, 2013     

Miscibility and transesterification in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

Miscibility and morphology of poly(ethylene 2,6‐naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) blends were studied by differential scanning calorimetry (DSC), optical microscopy (OM), proton nuclear magnetic resonance imaging (¹H‐NMR), and wide‐angle X‐ray diffraction (WAXD). OM and DSC results from ternary blends revealed the immiscibility of PEN/PPT/PEI blends, but ternary blends of all compositions were phase‐homogeneous following heat treatment at 300°C for over 60 min. Annealing samples at 300°C yielded an amorphous blend with a clear and single T_g at the final state. Experimental data from ¹H‐NMR revealed that PEN/PPT copolymers (ENPT) were formed by the so‐called transesterification. The effect of transesterification on glass transition and crystallization was discussed in detail. The sequence structures of the copolyester were identified by triad analysis, which showed that the mean sequence lengths became shorter and the randomness increased with heating time. The results reveal that a random copolymer improved the miscibility of the ternary blends, in which, the length of the homo segments in the polymer chain decreased and the crystal formation was disturbed because of the irregularity of the structure, as the exchange reaction proceeded. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3840–3849, 2006     

Isothermal crystallization behavior of nano-alumina particles-filled poly(ether ether ketone) composites

The isothermal crystallization behavior of nano-alumina particle-filled poly(ether ether ketone) (PEEK) composites has been investigated using differential scanning calorimeter. The results show that all the neat PEEK and nano-alumina-filled PEEK composites exhibit the double-melting behavior under isothermal crystallization. The peak crystallization times (τ_p) for all the neat PEEK and PEEK/aluminum oxide (Al₂O₃) composites increase with increasing crystallization temperature. Moreover, the crystallinity of the PEEK/Al₂O₃ composite with 7.5 wt % nano-filler content reached the maximum value of 44.8% at 290°C, higher than that of the neat PEEK polymer. From the lower value in τ_p and higher value in X_c for the PEEK/Al₂O₃ composites, the inclusion of the nano-alumina into the PEEK matrix favored the occurrence of heterogeneous nucleation. The Avrami exponents n of all the neat PEEK and PEEK/Al₂O₃ composites ranged from 2 to 3, and the n values for PEEK/Al₂O₃ composites were slightly higher than that of the neat PEEK polymer, indicating that the inclusion of the nano-filler made the crystallization mechanism more complex. However, the growth rate of crystallization was lowered as the nano- filler was introduced, and the decrease in growth rate reduced the grain size of the PEEK spherulites because of the lowering of molecule mobility during isothermal crystallization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

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     

含锌聚醚酯酰胺的热性能研究

以氧化锌、脂肪族二羧酸、聚乙二醇为原料合成含锌聚醚酯(PEEM),再将PEEM与聚己内酰胺低聚合物反应,制备含锌聚醚酯酰胺(PEEAM),借助差示扫描量热法(DSC)、热重(TG)分析,研究了PEEAM的热性能。结果表明:PEEAM呈双熔融和双结晶峰,随PEEM含量增加,PEEAM中PEEM链段的熔融温度降低,熔融热焓增大,聚酰胺链段的熔融温度略有下降,结晶放热和结晶温度随PEEM含量变化有最小值;PEEAM中含脂肪族二羧酸种类不同,其相应的熔融温度、熔融热焓、结晶温度及结晶放热不同,没有明显规律可循。脂肪族二羧酸种类对PEEAM的初始降解温度和最大质量损失温度没有明显影响。PEEM含量增大,PEEAM的热失重速率增大。     

Melting and crystallization behavior of PA1010/TPU blends

PA1010/TPU blends were prepared by melt blending. The melting, crystallization behavior, and isothermal crystallization kinetics were investigated using differential scanning calorimetry (DSC). The results showed that the DSC thermograms of blend samples exhibit double melting peaks. With increasing the TPU content, the position of the double melting peaks shifted to a lower temperature, and the total heat of fusion decreased. With increasing the heating rates, the position of the lower melting peak shifted to a higher temperature, while the position of the higher melting peak shifted to a lower temperature; however, the total heat of fusion remained almost constant. With prolonging the annealing time and increasing the crystallization temperature, the position of the lower melting peak shifted to a higher temperature, while the position of the higher melting peak almost did not change; however, the total heat of fusion increased. The addition of TPU could promote the crystallization of PA1010 but not affect the crystallization mechanism. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 839–844, 2004     

Miscibility and crystallization behavior of poly(ether ether ketone ketone)/poly(ether imide) blends

The miscibility and crystallization behavior of poly(ether ether ketone ketone) (PEEKK)/poly(ether imide) (PEI) blends prepared by melt‐mixing were investigated by differential scanning calorimetry. The blends showed a single glass transition temperature, which increased with increasing PEI content, indicating that PEEKK and PEI are completely miscible in the amorphous phase over the studied composition range (weight ratio: 90/10–60/40). The cold crystallization of PEEKK blended with PEI was retarded by the presence of PEI, as is apparent from the increase of the cold crystallization temperature and decrease of the normalized crystallinity for the samples anealed at 300°C with increasing PEI content. Although the depression of the apparent melting temperature of PEEKK blended with PEI was observed, there was no evidence of depression in the equilibrium melting temperature. The analysis of the isothermal crystallization at 313–321°C from the melt of PEEKK/PEI (100/0, 90/10, and 80/20) blends suggested that the retardation of crystallization of PEEKK is caused by the increase of the crystal surface free energy in addition to the decrease of the mobility by blending PEI with a high glass transition temperature. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 769–775, 2001     

Nonisothermal crystallization kinetics of nucleated poly(ethylene terephthalate)

Studies of the nonisothermal crystallization kinetics of poly(ethylene terephthalate) nucleated with anhydrous sodium acetate were carried out. The chemical nucleating effect was investigated and confirmed with Fourier transform infrared and intrinsic viscosity measurements. The Avrami, Ozawa, and Liu models were used to describe the crystallization process. The rates of crystallization, which initially increased, decreased at higher loadings of the additive. The activation energy, calculated with Kissinger's method, was lower for nucleated samples. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Melting behaviour of poly(butylene succinate) in miscible blends with poly(ethylene oxide)

The melting behavior of poly(butylene succinate) (PBSU) in miscible blends with poly(ethylene oxide) (PEO), which is a newly found polymer blends of two crystalline polymers by our group, has been investigated by conventional differential scanning calorimetry (DSC). It was found that PBSU showed double melting behavior after isothermal crystallization from the melt under certain crystallization conditions, which was explained by the model of melting, recrystallization and remelting. The influence of the blend composition, crystallization temperature and scanning rate on the melting behavior of PBSU has been studied extensively. With increasing any of the PEO composition, crystallization temperature and scanning rate, the recrystallization of PBSU was inhibited. Furthermore, temperature modulated differential scanning calorimetry (TMDSC) was also employed in this work to investigate the melting behavior of PBSU in PBSU/PEO blends due to its advantage in the separation of exotherms (including crystallization and recrystallization) from reversible meltings (including the melting of the crystals originally existed prior to the DSC scan and the melting of the crystals formed through the recrystallization during the DSC scan). The TMDSC experiments gave a direct evidence of this melting, recrystallization and remelting model to explain the multiple melting behavior of PBSU in PBSU/PEO blends.     

Crystallization and melt behaviour of isotactic poly(2-vinylpyridine)

The crystallization and melting behaviour of highly isotactic poly(2-vinylpyridine) (it-P2VP) with $\text{M}\text{?}{}_{\mathrm{<mtext>v</mtext>}}\text{= 4 × 10}{}^5$ has been studied by microscopy and d.s.c.. The maximum spherulitic growth rate was found to be 250 × 10^?3μm/min at a crystallization temperature T_c of 165°C. Experimental data could be described by the growth rate theory for small supercooling, by taking the appropriate value of 75 for the constant c₂ of the WLF equation. The chain-folded surface free energy σ_e, was estimated at 39.5 × 10^?3 J m^?2. The melting curves showed 1,2 or 3 melting endotherms. At large supercooling, crystallization from the melt produced a small melting endotherm just above T_c. This peak may originate from secondary crystallization of melt trapped within the spherulites. The next melting endotherm is related to the normal primary crystallization process. Its peak temperature increased linearly with T_c, yielding an extrapolated value for the equilibrium melting temperature T°_m of 212.5°C. At the normal values of T_c and heating rate a third endotherm appeared with a peak temperature that was independent of T_c, but rose with decreasing heating rate. From the effects of heating rate and partial scanning on the ratio of peak areas, it is concluded that this peak arises from secondary crystallization by continuous melting and recrystallization during the scan. This crystallization and melting behaviour of it-P2VP is very similar to that of isotactic polystyrene.     

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

Nonisothermal melt crystallization kinetics of PEDEKmK linked by meta-phenyl and biphenyl was investigated by differential scanning calorimetry (DSC). A convenient and reasonable kinetic approach was used to describe the nonisothermal melt crystallization behavior, and its applicability was verified when the modified Avrami analysis by the Jeziorny and Ozawa equation were applied to the crystallization process. The crystallization activation energy was estimated to be −219 kJ/mol by Kissinger method while crystallizing from the PEDEKmK melt nonisothermally. These observed crystallization characteristics were compared to those of the other members of poly(aryl ether ketone) family. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 815–821, 1998     

Isothermal crystallization and melting behaviors of bionanocomposites from poly(lactic acid) and TiO2 nanowires

Two representative poly(lactic acid) (PLA) nanocomposites with 1% TiO₂ nanowires were prepared through in situ melt polycondensation and easy solution‐mixing approaches, respectively. The former was denoted as ISPLANC, and the latter as SMPLANC. The isothermal crystallization kinetics and melting behaviors of pure PLA, ISPLANC, and SMPLANC were comparatively investigated by differential scanning calorimetry in the temperature range of 80–115°C. Maximum crystallization growth rate (G_exp) was observed at 100°C for all three samples. The well dispersed TiO₂ nanowires acted as effective nucleation agents in ISPLANC, which exhibited much higher G_exp in compared to pure PLA and SMPLANC below 110°C. However, much smaller crystallization enthalpy of ISPLANC was obtained because of its restricted chain mobility in forming crystalline lamellar. The crystallization behavior of all three samples fit the Avrami equation quite well, with most of the R² values larger than 0.9990. Double‐melting behaviors were observed after heating the samples after isothermal crystallization at various temperatures, which was explained by the melt recrystallization of the smaller and imperfect crystals formed at lower isothermal crystallization temperatures. We also obtained the equilibrium melting temperatures of the three samples by carrying out Hoffman–Weeks plots. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

不同温度熔融条件下聚对苯二甲酸乙二醇酯的结晶与熔融行为

分别采用低黏度和高黏度的聚对苯二甲酸乙二醇酯(PET)树脂切片,利用差示扫描量热分析(DSC)的方法研究不同的熔融温度条件对PET结晶行为和熔融行为的影响。结果表明:和高黏度PET相比,低黏度PET的结晶过程对熔融温度的变化极其敏感,不同熔融温度将对它的结晶行为与熔融行为产生显著的影响;在同等条件下,低黏度PET结晶速率快且易生成稳定的结晶结构,其稳定结晶的熔融温度要比高黏度PET高数度;总体上,采用较低的熔融温度有利于提高PET结晶温度和结晶速率,而采用较高的熔融温度有利于提高PET结晶的稳定性。     

Polymorphic crystallization of poly(butylene adipate) and its copolymer: Effect of poly(vinyl alcohol)

The crystallization kinetics and crystalline structure of the biodegradable polymorphic polymers, poly(butylene adipate) (PBA) and poly(butylene adipate‐co‐hexamethylene adipate), in the microparticles and nanoparticles covered by poly(vinyl alcohol) (PVA), and those on the PVA substrate were investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, and Fourier transform infrared spectroscopy. Both the polymers crystallized in the particle state and on the PVA substrate showed higher crystallization temperatures in the nonisothermal melt crystallization and shorter crystallization times in the isothermal crystallization; this indicated a faster crystallization of the polymer in the particle state and on the PVA substrate than that of the bulk sample. Furthermore, the polymers in the particle state and on the PVA substrate showed the preferential formation of the β‐type crystalline form of PBA compared to the bulk one. The mechanism for the effects of the PVA layer or substrate on the crystallization kinetics and crystalline structure of PBA and its copolyesters are discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39600.     

Influence of composition and molecular mass on the morphology,crystallization and melting behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends

Results are reported on the influence of composition and molecular mass of components on the isothermal growth rate of spherulites, on the overall kinetic rate constant, on the primary nucleation and on the thermal behaviour of poly(ethylene oxide)/poly(methyl methacrylate) blends. The growth rate of PEO spherulites as well as the observed equilibrium melting temperatures decrease, for a given T_c or ΔT, with the increase of PMMA content.Such observations are interpreted by assuming that the polymers are compatible in the undercooled melt, at least in the range of crystallization temperatures investigated. Thermodynamic quantities such as the surface free energy of folding σ_e and the Flory-Huggins parameter χ₁₂ have been obtained by studying the dependence of the radial growth rate G and of the overall kinetic rate constant K from temperature and composition and the dependence of the equilibrium melting temperature depression ΔT_m upon composition, respectively.     

Morphology and nonisothermal crystallization of a polyacetal/poly(ε‐caprolactone) reactive blend prepared via a chain‐transfer reaction

A polyacetal (POM)/poly(ε‐caprolactone) (PCL) reactive blend prepared via a chain‐transfer reaction was investigated with respect to its morphology and nonisothermal crystallization, and the results were compared with those of a simple POM/PCL blend. The reactive blend had a microscopically phase‐separated morphology in which the diameter of the PCL microphase was below 100 nm, and it clearly yielded ring‐banded spherulites, whereas between the two blends, there were no significant differences in the diameters and polygonal edges of the spherulites and in the long period of the POM phases. The PCL part of the reactive blend crystallized within the confined microspace with about 10% lower crystallinity than that of the corresponding simple blend. A lower Avrami exponent and crystallization rate parameter of the PCL part were observed in the primary crystallization process of the reactive blend. In contrast, the crystallinity of the POM component and the nonisothermal crystallization kinetic parameters of the POM part showed no noticeable differences between the two blends at any given cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008