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     

MC尼龙/Dy_2O_3纳米复合材料非等温结晶动力学

采用差示扫描量热法研究铸型(MC)尼龙/Dy_2O_3纳米复合材料的非等温结晶行为,并利用Caze法和Mo法对结晶动力学进行分析,运用Kissinger方法计算MC尼龙的结晶活化能.结果表明,纳米Dy_2O_3起到异相成核的作用,使MC尼龙的结晶峰温升高,结晶总速率增大;添加纳米Dy_2O_3使MC尼龙的结晶活化能增大.     

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     

Isothermal and nonisothermal crystallization kinetics of bio-sourced nylon 69☆

Bio-sourced nylon 69,one of promising engineering plastics,has a great potential in developing sustainable technology and various commercial applications.Isothermal and nonisothermal crystallization kinetics of nylon 69 is a base to optimize the process conditions and establish the structure–property correlations for nylon 69,and it is also highly bene ficial for successful applications of nylon products in industry.Isothermal and nonisothermal crystallization kinetics has been investigated by differential scanning calorimetry for nylon 69,bio-sourced even–odd nylon.The isothermal crystallization kinetics has been analyzed by the Avrami equation,the calculated Avrami exponent at various crystallization temperatures falls into the range of 2.28 and 2.86.In addition,the Avrami equation modi fied by Jeziorny and the equation suggested by Mo have been adopted to study the nonisothermal crystallization.The activation energies for isothermal and nonisothermal crystallization have also been determined.The study demonstrates that the crystallization model of nylon 69 might be a twodimensional(circular)growth at both isothermal and nonisothermal crystallization conditions.Furthermore,the value of the crystallization rate parameter(K)decreases signi ficantly but the crystallization half-time(t1/2)increases with the increase of the isothermal crystallization temperature.To nonisothermal crystallization,the crystallization rate increases as the cooling rate increases according to the analysis of Jeziorny's theory.The results of Mo's theory suggest that a faster cooling rate is required to reach a higher relative degree of crystallinity in a unit of time,and crystallization rate decreases when the relative degree of crystallinity increases at nonisothermal crystallization conditions.     

MC尼龙6/TiO2原位纳米复合材料等温结晶动力学的研究

采用差示扫描量热法(DSC)研究了阴离子原位聚合法制备的铸型尼龙6(MC尼龙6)/TiO2纳米复合材料的等温结晶行为,并应用Avrami方程分析了MC尼龙6的等温结晶动力学过程.结果表明纳米TiO2对MC尼龙6基体具有异相成核作用,使其原位纳米复合材料结晶速率常数变大,半结晶时间变小.Hoffman成核结晶理论计算结果表明,原位纳米复合材料的Kg(与结晶温度无关而与成核方式有关的参数)大于MC尼龙6且随着纳米含量的增加而增加,说明纳米TiO2阻碍了MC尼龙6分子链的运动,同时尼龙6由晶核生长占主导地位逐渐向成核机制占主导地位转变.     

Crystallization behavior of polyamide 11/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC) was used to investigate the isothermal and nonisothermal crystallization kinetics of polyamide11 (PA11)/multiwalled carbon nanotube (MWNTs) composites. The Avrami equation was used for describing the isothermal crystallization behavior of neat PA11 and its nanocomposites. For nonisothermal studies, the Avrami model, the Ozawa model, and the method combining the Avrami and Ozawa theories were employed. It was found that the Avrami exponent n decreased with the addition of MWNTs during the isothermal crystallization, indicating that the MWNTs accelerated the crystallization process as nucleating agent. The kinetic analysis of nonisothermal crystallization process showed that the presence of carbon nanotubes hindered the mobility of polymer chain segments and dominated the nonisothermal crystallization process. The MWNTs played two competing roles on the crystallization of PA11 nanocomposites: on the one hand, the MWNTs serve as heterogeneous nucleating agent promoting the crystallization process of PA11; on the other hand, the MWNTs hinder the mobility of the polymer chains thus retarding the crystal growth process of PA11. The activation energies of PA11/MWNTs composites for the isothermal and nonisothermal crystallization are lower than neat PA11. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

纳米二氧化硅／MC尼龙6原位复合材料非等温结晶动力学

通过阴离子开环聚合法制各纳米二氧化硅／MC尼龙6原位复合材料,采用差示扫描量热法研究MC尼龙6及其原位纳米复合材料非等温结品行为,并利用修正Avrami方程的Jeziomy和Liu的方法进一步处理原位纳米复合材料的非等温结晶动力学,结果表明在纳米二氧化硅／MC尼龙6原位复合材料中,纳米二氧化硅对基体MC尼龙6的结晶有一定的成核作用,并提高了其结品速率。     

Nonisothermal crystallization kinetics of polyamide 6 and ethylene‐co‐butyl acrylate blends

The nonisothermal melt‐crystallization behavior of PA6 and EBA blends at varying EBA content was investigated using differential scanning calorimetry at different scanning rates. Several macrokinetic models such as Avrami, Jeziorny, Ozawa, Liu, Ziabicki, and Tobin were applied to analyze the crystallization behavior thoroughly under nonisothermal conditions. The Avrami and Tobin model predicted that, for pure PA6 and PA6/EBA blends, simultaneous growth of all forms of crystal structures such as fibrillar, disc‐like, and spherulitic proceeds at an increasing nucleation rate. However, when applied to blends for isothermal crystallization, the Avrami model predicted that the crystallization process is diffusion‐controlled for pure PA6 and PA6/EBA blend containing higher content of EBA (50 phr), where the nylon‐6 chains were able to diffuse freely to crystallize under isothermal conditions. Liu model predicted that, at unit crystallization time, a higher cooling rate should be used to obtain a higher degree of crystallinity for both PA6 and PA6/EBA blends. The kinetic crystallizability of PA6 in the blends calculated using Ziabicki's approach varies depending upon the nucleation density and PA6‐rich regions present in the blend compositions. Nucleation activity of the blends estimated by Dobreva and Gutzowa method reveals that the EBA particles are inert at lower concentrations of EBA and do not act as nucleating agent for PA6 molecules in the blends. The activation energy of nonisothermal crystallization, calculated using Augis–Bennett, Kissinger, and Takhor methods indicated that the activation energy is slightly lower for the blends when compared to the neat PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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 crystallization kinetics of nylon 10 12

This article studied the crystallization behaviors of a newly industrialized polyamide, Nylon 10 12, under isothermal and nonisothermal conditions from the melt. A differential scanning calorimeter (DSC) was used to monitor the energetics of the crystallization process. During isothermal crystallization, relative crystallinity develops in accordance with the time dependence described by the Avrami equation with the exponent n=2.0. For nonisothermal studies, several different analysis methods were used to describe the crystallization process. The experimental results show that the Ozawa approach cannot adequately describe the nonisothermal crystallization kinetics. However, Avrami treatment for nonisothermal crystallization is able to describe the system very well. The calculated activation energy is 264.4 KJ/mol for isothermal crystallization by Arrhenius form and 235.5 KJ/mol for nonisothermal crystallization by Kissinger method.     

Isothermal crystallization kinetics and melting behavior of nylon/saponite and nylon/montmorillonite nanocomposites

DSC thermal analysis and X‐ray diffraction have been used to investigate the isothermal crystallization behavior and crystalline structure of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliating the layered silicates by subsequent polymerization. The DSC isothermal results reveal that introducing saponite into the nylon structure causes strongly heterogeneous nucleation induced change of the crystal growth process from a two‐dimensional crystal growth to a three dimensional spherulitic growth. But the crystal growth mechanism of nylon/montmorillonite nanocomposites is a mixed two‐dimensional and three‐dimensional spherulitic growth. The activation energy drastically decreases with the presence of 2.5 wt % clay in nylon/clay nanocomposites and then slightly increases with increasing clay content. The result indicates that the addition of clay into nylon 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). The correlation among crystallization kinetics, melting behavior, and crystalline structure of nylon/clay nanocomposites is also discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2196–2204, 2004     

纳米SiO_2/MC尼龙6原位复合材料等温结晶行为的研究

将纳米SiO2均匀分散在己内酰胺单体熔体中,采用阴离子开环聚合法制备了纳米SiO2/单体浇铸(MC)尼龙6原位复合材料。通过差示扫描量热仪(DSC)、Avrami方程、Lauritizen-Hoffmann方程对复合材料的等温结晶行为进行了研究。结果表明:纳米SiO2的引入改变了基体MC尼龙6的成核机理和生长方式;低含量的纳米SiO2阻碍了MC尼龙6的结晶行为,高含量的纳米SiO2降低了MC尼龙6的结晶活化能,提高了其球晶生长速率,并促进了其结晶行为。     

Isothermal and nonisothermal crystallization kinetics of partially melting nylon 10 12

Nylon 10 12, a newly industrialized engineering plastic, shows a double‐melting phenomenon during melting. Partial melts were obtained when the sample was heated to the temperature between the two melting peaks. A differential scanning calorimeter was used to monitor the energies of the isothermal and nonisothermal crystallization from the partially melted samples. During isothermal crystallization, relative crystallinity develops with a time dependence described by the Avrami equation, with the exponent n = 1.0. For nonisothermal studies, kinetics treatments based on the Avrami and Ozawa equations are presented to describe the crystallization process. It was found that the two treatments can describe the nonisothermal crystallization from the partially melted samples. The derived Avrami and Ozawa exponents are all about 1.0, which means that the partially melted samples crystallize by one‐dimensional growth, which may cause thickening of the lamellae. We calculated the crystallization activation energies for isothermal and nonisothermal crystallization from the partially melted samples. It was found that the activation energy determined by the Kissinger method was not rational, which may be attributed to the free‐nucleation process for nonisothermal crystallization from partially melted samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1311–1319, 2003     

Calorimetric and rheokinetic analyses merged to capture crystallization kinetics in polyamide/clay nanocomposites: Revisiting predictability of models

Crystallization kinetics of polymer/clay systems was the subject of numerous investigations, but still there are some ambiguities in understanding thermal behavior of such systems under isothermal and nonisothermal circumstances. In this work, isothermal rheokinetic and nonisothermal calorimetric analyses are combined to demonstrate crystallization kinetics of polyamide6/nanoclay (PA6/NC) nanocomposites. As the main outcome of this work, we detected different regimes of crystallization and compared them by both isothermal dynamic rheometry and nonisothermal differential scanning calorimetry (DSC), which has not been simultaneously addressed yet. A novel analysis, somehow different from the common ones, is used to convert the storage modulus data to crystallinity values leading to more reasonable Avrami parameters in isothermal crystallization. It was found based on isothermal rheokinetic studies that increase of NC content and shear rate are responsible for erratic behavior of Avrami exponent and crystallization rates. Optimistically, however, isothermal crystallization by rheometer was confirmed by DSC. Nonisothermal calorimetric evaluations suggested an accelerated crystallization of PA6 upon increasing NC content and cooling rate. The crystallization behavior was quantified applying Ozawa (r² between 0.070 and 0.975), and combinatorial Avrami–Ozawa (r² between 0.984 and 0.998) models, where the latter appeared more appropriate for demonstration of nonisothermal crystallization of PA6/NC nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46364.     

PPES/MC尼龙6中相互作用对MC尼龙6的结晶及熔融行为影响

采用原位共混与溶液共沉淀两种不同的方法制得了PPES/MC尼龙6共混物。通过对共混物的DSC非等温结晶与熔融行为表征,推出共混物之间的相互作用。结果表明两种共混物中PPES对MC尼龙6的结晶都起阻碍作用,溶液共混物中熔融峰温(Tm)相对于MC尼龙6变化不大,而其在原位共混物中的影响很大,使得MC尼龙6的熔融峰温(Tm)向高温移动。更值得注意的是,原位共混物中MC尼龙6的结晶与熔融峰温相对于溶液共沉淀样品中偏移纯MC尼龙6的峰温更明显,说明原位共混物中PPES与MC尼龙6之间的相互作用大于溶液共沉淀共混物中的PPES与MC尼龙6的相互作用。在溶液共沉淀中MC尼龙6的结晶和熔融峰温均比在原位共混物中的高。     

Studies on crystallization kinetics of nylon 6-polyoxypropylene-nylon 6 copolymers

The crystllization kinetics of anionic-prepared nylon6-poly(oxypropylene) 1000-nylon 6 (NPN) block copolymers containing 1.20 to 8.76 wt% poly(oxypropylene)(POP) were studied. The thermograms of isothermal and nonisothermal differential scanning calorimetry of NPN block copolymers obtained were used for the study. The Avrami equation was used to analyze the isothermal crystallization of NPN nylon block copolymers. The Avrami exponent n obtained in the temperature range of 180 to 200 °C was 2.0 to 2.5. It was not similar to that for nylon 6 reported in literature. The activation energies of crystallization for the nylon block copolymers were smaller than that of nylon 6, and showed a minimum with POP content. The equilibrium melting point increased as the POP content decreased. For the nylon block copolymers with lower POP content, the slopes of T_c vs. T_m plots were higher than the values reported elsewhere. The Ozawa plot was used to analyze the data of nonisothermal crystallization. The obvious curvature in the plot indicated that the Ozawa model could not fit our system well, and there was an abrupt change of the slope in the Ozawa plot at a critical cooling rate.     

半芳香族聚酰胺6T/6I/6的合成及其非等温结晶动力学研究

采用成盐、高温溶液缩聚两步法成功制备了半芳香族聚酰胺（PA）6T/6I/6。通过傅里叶变换红外光谱（FTIR）、氢核磁共振（¹H⁃NMR）分析了其分子链结构,并对其力学性能进行了测试表征,利用差示扫描量热法（DSC）对PA6T/6I/6的非等温结晶动力学进行了研究,使用Jeziorny法、Oazawa法和莫志深法修正的Avrami方程分别分析了PA6T/6I/6的非等温结晶行为。结果表明,通过Jeziorny法处理发现结晶过程分为主期结晶和次期结晶2个阶段,主期结晶阶段Avrami指数在1.08~1.09之间,晶体为异相成核,呈一维针状生长,次期结晶阶段Avrami指数在2.13~2.21之间,晶体为二维片状生长方式;Ozawa法处理曲线相关性低,表明不适用于描述PA6T/6I/6的非等温结晶过程;莫志深法修正的Avrami方程能较好地描述结晶过程,a值在0.89~0.90之间,F（T）值在7.24~15.85之间;采用Kissinger方程计算求得PA6T/6I/6的非等温结晶活化能为-294.17 kJ/mol。     

Effect of ultrafine,fully vulcanized acrylate powdered rubber on the mechanical properties and crystallization behavior of nylon 6

Nylon 6 (PA6) is a widely used engineering plastic. However, its poor toughness limits its applications. Therefore, toughening PA6 has been a point of interest in the field of PA6 modification. Generally, toughening a plastic with an elastomer reduces the stiffness and heat distortion temperature of the matrix. It has been an important goal of polymer researchers to find a way of toughening PA6 without reductions in its stiffness and heat distortion temperature. In this study, a new kind of material—an ultrafine, fully vulcanized acrylate powdered rubber (UFAPR)—was used to toughen PA6 through melt blending. The influence of UFAPR on the isothermal crystallization kinetics and nonisothermal crystallization behavior of PA was studied with differential scanning calorimetry. The results showed that, with the addition of a little UFAPR, the crystallization rate of PA could be increased, the crystallization temperature could be augmented, and the crystal size distribution of the crystal grain could be narrowed. The changes in the free energy perpendicular to the crystal nucleus were consistent with the results of an Avrami equation according to the theory of Hoffman. The unit surface free energy of the radially developing crystal spherulites decreased with an increasing amount of UFAPR. The results for the mechanical properties, crystalline structure, and crystallization kinetics of PA6/UFAPR composites showed that UFAPR was not only a good toughening agent for PA6 but also an excellent nucleation agent for PA6. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3503–3511, 2003     

Nonisothermal crystallization kinetics of flame‐sprayed polyamide 1010/nano‐ZrO2 composite coatings

Polyamide1010 (PA1010) and its composite with nanometer‐sized zirconia (PA1010/nano‐ZrO₂) coatings were deposited using a flame spray process. The kinetics of nonisothermal crystallization of PA1010/nano‐ZrO₂ composite coatings was investigated by differential scanning calorimetry (DSC) at various cooling rates. Several different analysis methods were used to describe the process of nonisothermal crystallization. The results showed that the modified Avrami equation and Mo's treatment could describe the nonisothermal crystallization of the composite coatings very well. The nano‐ZrO₂ particles have a remarkable heterogeneous nucleation effect in the PA1010 matrix. The values of halftime and Z_c showed that the crystallization rate increased with increasing cooling rates for both PA1010 and PA1010/nano‐ZrO₂ composite coating, but the crystallization rate of PA1010/nano‐ZrO₂ composite coating was faster than that of PA1010 at given cooling rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007