苯乙烯-丙烯等规立构嵌段共聚物(iPS-b-iPP)的非等温结晶动力学的研究

用DSC法研究了苯乙烯-丙烯等规立构嵌段共聚物的非等温结晶动力学。结果表明:冷却速率在5～20℃/min范围内,共聚物的非等温结晶动力学参数能很好地符合Avrami动力学方程,非等温结晶速率常数与冷却速率有关,动力学结晶能力则同时受到冷却速率和共聚物组成比的影响。文中还讨论了在非等温结晶条件下共聚物的结晶成核和生长方式与共聚物组成和结构的关系。联合Avrami方程和Ozawa方程推导的非等温结晶动力学方程较好地描述了iPS-b-iPP嵌段共聚物的非等温结晶动力学过程。     

取向聚对苯二甲酸乙二酯纤维的非等温结晶动力学

取向聚对苯二甲酸乙二酯纤维的非等温结晶动力学张志英，赵家森（天津纺织工学院材料科学系天津３００１６０）关键词取向高聚物，聚对苯二甲酸乙二酯，非等温结晶，结晶动力学研究高聚物结晶动力学常用的等温方法有光透射法、密度法、显微镜法、Ｘ－射线衍射法、差示扫描...     

Effect of Electron Beam Irradiation on the Kinetics of Non-isothermal Crystallization of Nylon 66

The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66.     

Non-isothermal melt crystallization kinetics for ethylene-acrylic acid copolymers and ethylene-methyl acrylate-acrylic acid terpolymers

Non-isothermal melt crystallization kinetics and subsequent melting behavior for four different grades of ethylene-acrylic acid copolymer and three different grades of ethylene-methyl acrylate-acrylic acid terpolymer was investigated by differential scanning calorimetry technique. The non-isothermal melt crystallization data were analyzed based on the Ozawa and Ziabicki macrokinetic models. The effective energy barriers describing non-isothermal melt crystallization process for these resins were determined based on the differential iso-conversional method of Friedman. The amount of non-crystallizable, intra-molecular defects had substantial effects on the non-isothermal melt crystallization kinetics and subsequent melting behavior.     

Computer simulation of crystallization kinetics and morphology in fiber-reinforced thermoplastic composites. I. Two-dimensional case

A body of experimental evidence suggests that reinforcing fibers influence both the crystallization kinetics and morphology of those composite materials that are based on crystallizable thermoplastics. The absence of an analytical model to predict the effect of fibers on crystallization has hindered data analysis. A new approach, using computer simulation of polymer crystallization, makes it possible to study the influence that reinforcing fibers have on the crystallization kinetics and morphology of semicrystalline polymers. Fibers depress the crystallization rate relative to an unreinforced polymer since they constrain spherulitic growth by an impingement mechanism. On the other hand, reinforcing fibers can also enhance crystallization rate by providing added surface nucleation sites. This work describes a two-dimensional simplification of the crystallization process that occurs in bulk materials. It is demonstrated that the relative bulk and fiber nucleation densities, in addition to the fiber fraction, fiber diameter, and spherulitic growth rate control the crystallization kinetics and also the spherulitic and transcrystalline morphologies that develop in reinforced thermoplastic composites. © 1993 John Wiley & Sons, Inc.     

乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学

通过差示扫描量热仪(DSC)研究了乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学,用Jeziorny和Ozawa方程描述了结晶动力学过程.共混物的结晶温度和结晶焓强烈依赖于淀粉含量和冷却速率.结果表明,随着冷却速率的增加,每个试样的结晶放热曲线均变宽,并向低温区移动.当温度一定高时,所有试样均具有较快的结晶速率. Jeniorzy方程可以较好地描述POE/淀粉共混物的非等温结晶模式,而Ozawa方程对于POE/淀粉共混体系不太适合.     

低密度聚乙烯/乙丙烯三元共聚(LDPE/EPO)共混体系的结晶动力学

用DSC方法研究了LDPE/EPO共混体系的等温及非等温结晶动力学,对LDPE/EPO共混体系的等温结晶动力学研究表明,共混物是三维生长的异相成核,共混物在各个结晶温度下的结晶过程都是以方式K_g(Ⅱ)进行的.采用联系Avrami方程和Ozawa方程导出的新非等温结晶动力学方程,处理了LDPE/EPO共混体系,得到了非等温结晶过程的一些基本参数,新方程很好地描述了此共混体系的非等温结晶动力学过程.     

Interpretation of the nonisothermal crystallization kinetics of polypropylene using a power law nucleation rate function

A nucleation rate function is proposed for use in analyzing the overall crystallization kinetics of polymers. This function allows for the possibility that the nucleation rate varies substantially during the crystallization. This feature is particularly useful in analyzing nonisothermal crystallization, but it can be used to analyze isothermal crystallization as well. The nucleation rate function was used in the derivation of a modified transformation kinetics equation of the Avrami type. The modified Avrami equation was found to be suitable for kinetics analysis for the data obtained from nonisothermal crystallization at rapid cooling rates. Kinetics parameters used to describe nonisothermal crystallization under rapid cooling rates are presented and discussed. These include crystallization induction time, plateau (crystallization) temperature, crystallization half-time, crystallization rate constant, Avrami index, and newly defined quantities called nucleation index, geometric index, and nucleation rate constant. The procedure used to obtain the nucleation rate constant and nucleation index for the nucleation rate function is described and illustrated by application to the analysis of the crystallization kinetics of polypropylene. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1077–1093, 1997     

Fundamental aspects of stress,deformation, and phase transitions in crystallizable polymers: Experiments with poly(ethylene terephthalate) in uniaxial stress fields

Interactions between rheology and fluid→solid transformations through crystallization are demonstrated through an experimental study of crystallization of polyethylene terephthalate in uniaxial stress fields. Effect of the strength of the stress field on the kinetics of crystallization is shown to diminish greatly beyond the initiation of crystallization. Consequences of crystallization in anisotropic stress fields in the generation of mechanical properties are also described. This experimental study points clearly to the deficiencies in current theoretical formulations of kinetics of crystallization.     

Isothermal and nonisothermal crystallization kinetics of novel biobased poly(ethylene succinate-<Emphasis Type="Italic">co</Emphasis>-ethylene sebacate) copolymers from the amorphous state

In this work, the isothermal and nonisothermal crystallization kinetics of three novel biobased poly(ethylene succinate-co-ethylene sebacate) (PESSe) copolymers was systematically investigated with differential scanning calorimetry under different crystallization conditions from the amorphous state. For the isothermal cold crystallization kinetics study, the Avrami equation could well describe the crystallization process of PESSe at various crystallization temperatures. All three PESSe copolymers crystallized through the same crystallization mechanism; moreover, the overall isothermal cold crystallization rate of PESSe decreased with increasing ethylene sebacate (ESe) comonomer content. The nonisothermal cold crystallization kinetics of PESSe was also studied at different heating rates. With increasing ESe content or heating rate, the nonisothermal cold crystallization exotherm of PESSe copolymers shifted to high temperature range. Both the crystallization rate parameter and crystallization rate coefficient of PESSe copolymers decreased with increasing ESe content, indicating that PESSe copolymer with higher ESe content crystallized more slowly than that with lower ESe content. The Ozawa equation was used to analyze the nonisothermal cold crystallization kinetics of PESSe copolymers, which was found to fit the crystallization process very well.     

半结晶聚合物注射成型中结晶动力学的数值模拟

对半结晶聚合物注射成型过程及其结晶过程进行偶合模拟,分析了二者的相互影响.具体是在注射成型数值模拟中考虑结晶动力学效应,分别在本构方程、能量方程及材料物性参数方程中引入反映结晶效应的参数;同时在结晶动力学计算中考虑流动诱导效应,从能量的角度提出并使用修正的动力学模型,用材料流动过程的耗散能表征流动对结晶的影响.通过对等规聚丙烯(iPP)和聚对苯二甲酸乙二醇酯(PET)两种半结晶聚合物注射过程模拟结果的分析比较,证实成型过程具有加速结晶的作用.同时,材料的结晶也对注射成型加工过程,尤其是保压与冷却过程的温度场分布有较大的影响.     

Stop-and-return DSC method to study fat crystallization

Differential scanning calorimeters have frequently been used to study the isothermal crystallization kinetics of fats and oils. In some circumstances (e.g. start of crystallization during cooling to the crystallization temperature, crystallization in emulsion) this straightforward approach is not applicable. This paper describes an indirect DSC method for determination of the crystallization kinetics under these ‘difficult’ circumstances. The principle is to stop the crystallization at different moments during the isothermal crystallization and raise the sample temperature. The amount of heat released is then used as a measure for the amount of crystallization and plotted as function of time. Combination of the stop-and-return method with the direct method may sometimes be used to save on measurement time. Stop-and-return experiments can furthermore be used to gain more insight in the crystallization mechanism based on the fact that different polymorphic forms and fractions have different melting temperatures.     

Non-isothermal crystallization kinetics of UHMWPE composites filled by oligomer-modified CaCO3

The processability of ultrahigh molecular weight polyethylene (UHMWPE) improved by oligomer-modified calcium carbonate (CaCO₃) was observed in our previous work. In order to understand the effect of oligomer-modified CaCO₃ on the crystallization of UHMWPE, the non-isothermal crystallization behavior and crystallization kinetics of UHMWPE composites filled by oligomer-modified CaCO₃ was studied by differential scanning calorimetry in this work. Jeziorny and Mo methods were used to describe the non-isothermal crystallization kinetics of UHMWPE composites. The effect of modified filler content and cooling rate on the crystallization temperature and crystallization rate was discussed. The heterogeneous nucleation of modified CaCO₃ slightly increases the crystallization temperature of UHMWPE. The crystallization enthalpy of UHMWPE composites is significantly higher than that of UHMWPE. The crystallization rate of UHMWPE composites depends on the filler contents and cooling rate.

     

From surface self-assembly to crystallization: prediction of protein crystallization conditions

A new criterion based on surface and volume diffusion kinetics was established to predict protein crystallization. Similar to the layer-by-layer crystal growth process of protein, the kinetics of the two-dimensional self-assembly of protein at the aqueous solution surface provides a convenient and reliable way to estimate the surface integration and the volume transport during protein crystallization. Both the surface and diffusion kinetics were estimated based on the protein self-assembly at the air/solution interface, which can be obtained by measuring the surface tension. A crystallization coefficient is found to provide an effective and reliable criterion to predict protein crystallization conditions. This criterion has been applied to lysozyme, concanavalin A and BSA crystallization, and it turns out to be very successful and more reliable than the second virial coefficient criterion.     

The effect of the incident collision energy on the phase and crystallization kinetics of vapor deposited water films

Molecular beam techniques are used to grow water films on Pt(111) with incident collision energies from 5 to 205 kJ/mole. The effect of the incident collision energy on the phase of vapor deposited water films and their subsequent crystallization kinetics are studied using temperature programmed desorption and infrared spectroscopy. We find that for films deposited at substrate temperatures below 110 K, the incident kinetic energy (up to 205 kJ/mole) has no effect on the initial phase of the deposited film or its crystallization kinetics. Above 110 K, the substrate temperature does affect the phase and crystallization kinetics of the deposited films but this result is also independent of the incident collision energy. The presence of a crystalline ice template (underlayer) does affect the crystallization of amorphous solid water, but this effect is also independent of the incident beam energy. These results suggest that the crystallization of amorphous solid water requires cooperative motion of several water molecules.     

Crystallization behavior of biodegradable poly(ethylene adipate) modulated by a benign nucleating agent: Zinc phenylphosphonate

Zinc phenylphosphonate (PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate) (PEA) to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA. Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly. Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn. In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly. It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA. The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.     

一种研究聚合物非等温结晶动力学的方法

作者基于多年对聚合物结晶动力学方面研究的工作积累,联合Avrami方程和Ozawa方程,提出了一种研究聚合物非等温结晶动力学的新方法.该方法既克服了使用Ozawa方程所获得的数据点过少,常常出现非线性,不能获得可靠的动力学参数的缺点,又克服了使用经Jeziorny修正的Avrami方程所获得的表观Avrami指数无法准确预测非等温过程成核生长机理的缺点.该方法已成功用于多种聚合物体系,被国内外学者引用数百次,已成为研究聚合物非等温结晶动力学一种有效方法.     

Computer simulation of crystallization kinetics and morphology in fiber-reinforced thermoplastic composites. II. Three-dimensional case

A three-dimensional computer simulation has been used to predict crystallization kinetics and crystalline morphology in composite materials that are based on crystallizable thermoplastics. Reinforcing fibers in three-dimensional simulations show similar behavior to those in two-dimensional simulations; fibers suppress crystallization relative to an unreinforced polymer since they constrain spherulitic growth by an impingement mechanism, and also enhance crystallization by providing added surface nucleation sites. The effects of varying controlling parameters on crystallization kinetics and morphology are qualitatively the same as those observed in the two-dimensional case. The relative bulk and fiber nucleation denisities, in addition to the fiber volume fraction, fiber diameter, and spherulitic growth rate control the crystallization kinetics and crystalline morphology that develop in reinforced thermoplastic composites. It is more difficult to achieve the transcrystalline morphology in slices of three-dimensional composites than it is in two-dimensional composites because nuclei in 3-D systems are not constrained to positions in or near a 2-D plane. © 1993 John Wiley & Sons, Inc.     

Reflection–absorption infrared spectroscopy investigation of the crystallization kinetics of poly(ethylene terephthalate) ultrathin films

Reflection–absorption infrared spectroscopy was used to study the crystallization behavior of poly(ethylene terephthalate) (PET) ultrathin films. The crystallinity of ultrathin films was estimated by the fraction of trans conformers of PET. The isothermal and nonisothermal crystallization kinetics of ultrathin films with different thicknesses were investigated. The thinner PET film showed slower kinetics during isothermal crystallization than the thicker film. Moreover, the final crystallinity of films with various thicknesses were reduced with decreasing thickness. An Avrami equation was used to fit the acquired results. The Avrami exponents decreased with the film thickness. As for the nonisothermal crystallization, the cold‐crystallization starting temperature shifted to a lower temperature as the film thickness increased. The influence of the substrate on the crystallization kinetics of the films was also studied. The half‐crystallization times and final crystallinities of ultrathin films adsorbed onto a self‐assembled‐monolayer‐treated surface and an untreated substrate were clearly different, although their thickness dependence was similar. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4440–4447, 2004     

Crystallization Kinetics of Polypropylene and Poly (butyl methacrylate-co-hydroxyethyl methacrylate) Blend

The crystallization kinetics of polypropylene and poly (butyl methacrylate-co-hydroxyethyl methacrylate) blend was investigated with differential scanning calorimetry. The isothermal crystallization analysis based on the Avrami theory indicated a heterogeneous nucleating effect from the copolymer. A systematic study of the nonisothermal crystallization kinetics was undertaken using the Avrami equation and its later modifications by Ozawa, Mo, and Zhang. The results demonstrated that the linear relationship failed in the different cooling rates because the Avrami method did not take into account that the crystallization temperature was lowered continuously. The Ozawa and Mo methods could be successful in describing the overall nonisothermal process of polypropylene and the blend. In addition, the nonisothermal crystallization energy values were estimated by the Kissinger and Freidman models. There are two mutually opposite effects on the crystallization behavior of the blend: nucleation ability and growth retardation.