聚乳酸/纳米SiO_2复合材料的熔融和冷结晶行为

采用熔融共混法制备了聚乳酸(PLLA)/纳米SiO2复合材料;利用透射电镜观察了复合材料的微观形貌;利用差示扫描量热仪测定了该复合材料的熔融行为和非等温冷结晶行为;利用Jeziorny法和Mo法研究了PLLA及其复合材料的非等温冷结晶动力学.结果表明,纳米SiO2在PLLA基体中具有良好的分散性和异相成核作用,使得PLLA基体的结晶峰向低温方向移动;复合体系的熔融温度和熔融焓的变化与SiO2的加入量密切相关.采用Jeziorny法和Mo法均可以很好地处理复合材料的非等温冷结晶过程.     

尼龙纳米复合材料研究进展

综述了尼龙纳米复合材料的制备方法、性能特点以及近几年来国内外对尼龙纳米复合材料产品开发进展情况。重点从纳米粒子对复合材料结晶行为的影响以及纳米粒子与尼龙界面相互作用两方面研究纳米粒子增强增韧尼龙的机理。并展望了尼龙纳米复合材料的应用前景。     

尼龙6/蒙脱土纳米复合材料的等温结晶动力学研究

用ＤＳＣ法研究了熔体插层制备的尼龙６／蒙脱土纳米复合材料的等温结晶行为．结果表明,加入少量的蒙脱土可明显提高尼龙６的结晶速率,降低球晶径向生长的单位面积表面自由能．从Ａｖｒａｍｉ方程和Ｈｏｆｍａｎ理论出发,得出蒙脱土纳米粒子的存在可明显改变尼龙６的结晶行为     

可分散性纳米SiO2/尼龙1010复合材料的结晶行为

采用熔融共混法制备了可分散性纳米SiO2/尼龙1010复合材料.通过X射线衍射和差示扫描量热法对尼龙1010及其复合材料的结晶行为进行了研究.结果表明,SiO2的加入作为结晶的异相成核点,使复合材料的结晶温度升高,熔融温度降低,使其结晶度稍有降低;SiO2的加入并没有改变尼龙1010的结晶形态,只是使尼龙1010的晶格尺寸发生了一定程度的改变.     

聚丙烯/层状双氢氧化物纳米复合材料研究进展

聚丙烯/层状双氢氧化物纳米复合材料是近年来开发的新型聚合物基复合材料,具有与纯聚合物基体不同的结晶行为,而且表现出优异的机械力学性能、耐热性能、阻燃性能和耐紫外线功能等,有着广泛的应用前景。本文首先对层状双氢氧化物的结构、组成与制备方法进行简要介绍,然后重点阐述了聚丙烯/层状双氢氧化物纳米复合材料的制备、分散结构表征、结晶行为以及力学和热学等性能方面的研究进展,最后对其应用前景进行展望。     

聚丙烯基纳米碳纤维复合材料结晶行为研究

采用示差扫描量热法(DSC)研究了纳米碳纤维对PP／CNF复合材料中PP结晶行为的影响。结果表明：纳米碳纤雏可提高PP的结晶温度，但略降低其结晶速率和结晶度。提高纳米碳纤雏含量或减小纳米碳纤雏直径，PP结晶行为的上述变化更为明显，但结晶速率随纳米碳纤维含量出现先减小后增大的趋势。     

聚萘并噁嗪/蒙脱土纳米复合材料的制备与表征

用原位插层反应法地制备了聚萘并嗪 蒙脱土纳米复合材料 .采用X ray衍射 (XRD)及透射电镜(TEM)研究复合材料中蒙脱土硅酸盐片层间距 ,发现硅酸盐片层间距由 1 2 6nm扩增至 5 88nm以上 .同时研究了该复合材料的耐热性 ,并探讨了复合材料的结晶行为     

聚乙烯醇/层状双氢氧化物纳米复合材料研究进展

聚乙烯醇/层状双氢氧化物纳米复合材料是近年来开发的新型聚合物基复合材料,表现出与纯聚乙烯醇基体明显不同的结晶行为,且具有良好的机械力学性能、耐热性能以及阻燃性能等,有着广泛的应用前景。本文首先对层状双氢氧化物的结构组成、制备方法和性质进行简要综述,然后着重介绍聚乙烯醇/层状双氢氧化物纳米复合材料的制备、结构表征、结晶行为、力学和热性能等方面的研究进展,最后对其应用前景进行展望。     

具有包藏结构的三元聚丙烯纳米复合材料结构与性能关系的研究

制备了一种新型聚丙烯 丁苯橡胶 纳米碳酸钙三元纳米复合材料 .研究结果显示 ,复合材料中的大多数纳米碳酸钙粒子被包藏在丁苯橡胶中 ,并与之共同形成分散于聚丙烯树脂中的分散相 ,这种聚丙烯纳米复合材料具有高刚性、高韧性、高耐热性和高的结晶速率 .系统研究了成核剂苯甲酸钠的加入和纳米碳酸钙的用量对该类纳米复合材料相态结构、结晶形态和结晶动力学的影响 ,以及具有包藏结构的分散相粒径和PP中β晶含量对材料性能的影响 .结果表明 ,苯甲酸钠的加入和纳米碳酸钙用量的提高均可使体系中分散相粒径减小 ,结晶速率加快 ,进而使材料的韧性、刚性和耐热性提高 .     

聚丙烯/无机纳米粒子复合材料的发泡行为

利用型腔体积可控注塑发泡装备制备聚丙烯/无机纳米粒子微发泡复合材料,通过复合材料的流变行为和结晶行为,分析了无机纳米粒子对聚丙烯发泡行为的影响。结果表明:无机纳米粒子有促进气泡异相成核作用,同时无机纳米粒子引入可以提高聚丙烯黏弹响应和降温结晶起始温度,起到了抑制泡孔结构恶化的作用,显著改善了聚丙烯的泡孔结构;在聚丙烯材料中添加纳米CaCO3、纳米OMMT、纳米SiO2进行发泡,以PP/OMMT发泡材料的发泡质量最理想,其泡孔密度和尺寸分别为2×106个/cm3和24.2μm。     

Crystallisation of polypropylene matrix in composites filled with wooden parts of rapeseed straw

Nucleation ability of native and modified rapeseed straw during the polypropylene crystallization from the melt was investigated by the DSC method. Composites were made from isotactic polypropylene and lignocellulosic material using extrusion and injection moulding techniques. They were obtained using polypropylenes differing with respect to melt flow rates and different varieties of rapeseed straw. Chemical modification was carried out in two stages: through mercerisation and treatment with acetic acid anhydride. In the course of investigations, it was found that both native and modified rapeseed straw acted as an active nucleant of polypropylene crystallisation characterised by low values of MFR indices. It was found that for polypropylenes with high MFR values, the values of crystallization temperatures and crystallization half-time in composites were identical when compared with non-filled polymers. The investigations demonstrated that there were insignificant differences among composites containing straw from different varieties of rapeseed. The analysis of crystallization temperatures confirmed that rapeseed straw modification failed to change this parameter of the crystallization process. A similar tendency was observed in the case of changes of the half-time crystallization process. Moreover, the analysis of the crystallization temperature and crystallization half-time showed that the presence in composites of lignified rapeseed straw particles played an important role in the crystallization conditions.     

Effect of silver nanoparticles on the morphology,crystallization, and melting behavior of polypropylene: A study on non-isothermal crystallization kinetics

The nanocomposites were prepared using melt intercalation method and the effects of the processing conditions on silver nanoparticles dispersion were investigated by transmission electron microscopy. Non-isothermal crystallization kinetics of virgin polypropylene (PP) and its nanocomposites have been evaluated using differential scanning calorimetric technique. The non-isothermal crystallization melt data were analyzed using macro kinetics equation with the help of Avrami, Malkin, and Mo’s models. The crystallization rate increased with the increasing of cooling rates for virgin PP and nanocomposite, but the crystallization of nanocomposite was faster than that of PP at a given cooling rate. The activation energy for non-isothermal crystallization of virgin polymer and nanocomposites based on Kissinger method has been determined to be 186 and 211 kJ/mol, respectively. Transmission electron microscopy analysis reveals balanced dispersion and presence of some silver nanoparticles aggregates, which act as a heterogeneous nucleating agent during the crystallization of the nanocomposite.     

MCM-41介孔分子筛合成研究Ⅰ.水热合成法

以 十六 烷基 三甲 基溴 化铵 为附 加试 剂合 成了 Ｍ Ｃ Ｍ４１ 介 孔分 子筛, 并 用 Ｘ Ｒ Ｄ , Ｓ Ｅ Ｍ 和 Ｉ Ｒ 等 表征手段 考察了晶 化时间 、晶化温度 、物料 组 成和 附 加试 剂用 量 等对 其晶 化 过程 的影 响． 结果表明 , Ｍ Ｃ Ｍ４１ 介孔分 子筛的晶 化诱导 期较长,在 晶化后 期存在着 转晶现 象,而且有 一较适 宜的晶化温 度、物料 组成和附 加试剂 用量范围     

SYNTHESIS AND CRYSTALLIZATION BEHAVIOR OF POLY(ETHER ETHER KETONE ETHER KETONE)(PEEKEK)*

In this paper, the synthesis and crystallization behavior of poly(ether ether ketone ether ketone) (PEEKEK) arereported. PEEKEK was prepared from 4,4'-bis(p-fluorobenzoyl) diphenyl ether (4,4'-FBDE) and hydroquinone along thenucleophilic substitution route. The thermal properties were investigated by using DSC and TGA. The crystallizationbehavior of PEEKEK under several conditions, i.e., crystallization from the molten state (melt crystallization), crystallizationfrom a quenched sample (cold crystallization) and crystallization induced by exposing glassy sample to methylene chloride(solvent-induced crystallization) has also been investigated. The results show that crystallization of PEEKEK could beinduced by the above methods, and no polymorphism was found. The diflierences in the crystallization of PEEKEK inducedby the above methods are seen in their degree of crystallinity.     

Cold crystallization and postmelting crystallization of PLA plasticized by compressed carbon dioxide

The cold crystallization at temperature T_cc (melting > T_cc > glass transition) and the postmelting crystallization of polylactic acid plasticized by compressed carbon dioxide (CO₂) were studied using a high-pressure differential scanning calorimeter. The kinetics of the two kinds of crystallization were evaluated by the Avrami equation as a function of pressure at certain temperatures. The effects of using talc as a nucleation agent on the two types of crystallization under pressure were also investigated. The results show that compressed CO₂ increased the mobility of the polymer chains in solid state, resulting in an increased rate of cold crystallization. The decreased rate of postmelting crystallization was mainly in the nucleation-controlled region, which indicates that the number of nuclei was decreased by the compressed CO₂. The growth rate of the two crystallization types followed the Avrami equation, but the kinetics of each depended upon temperature and pressure. The inclusion of talc accelerated postmelting crystallization but had little effect on cold crystallization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2630–2636, 2008     

Nonisothermal crystallization and melting behavior of the copolymer derived from p-dioxanone and poly(ethylene glycol)

Nonisothermal crystallization and melting behaviors of poly(p-dioxanone)(PPDO)-b-poly(ethylene glycol)(PEG) with mole ratios of 80:20 and 30:70, has been studied by differential scanning calorimeter using various cooling rates. Crystallization behavior of each crystallizable segments of the copolymer was compared with the corresponding segment of homopolymer. For a given composition, the crystallization process began at higher temperature when the slower scanning rates were used. The kinetics of the PPDO segments and the PEG segments in the copolymers under nonisothermal crystallization conditions were analyzed by Ozawa equation and also the crystallization results of the copolymer segments were compared with the corresponding homopolymers. The results showed that the Ozawa equation fails to describe the whole crystallization process of the copolymer segments along with PPDO homopolymer, but describes the crystallization behavior of the PEG homopolymer. Crystallization activation energy and absolute crystallinity values were estimated from the cooling scans (using Kissinger’s method) and fusion endotherms of the subsequent heating scans, respectively.     

An efficient organic additive to control the crystallization rate of aliphatic polyketone: A non-isothermal crystallization kinetics study

Three types of organic compounds—two carboxylic acids and an anhydride, were used as additives for polyketone(PK). The effect of the additive structure and their feed ratios on the melting temperature, crystallization temperature, and crystallization rate of PK were studied. We found that the crystallization temperature could be reduced significantly by introducing a small quantity of organic additive, in particular, an anhydride. On addition of 1 phr of anhydride, the crystallization temperature was reduced by 10.7 ℃. Therefore, the non-isothermal crystallization kinetics of aliphatic PK/anhydride blends with various feed ratios was investigated using DSC. The results were analyzed by various theoretical models, such as Avrami, Ozawa and combined Avrami-Ozawa models.     

Isothermal and nonisothermal crystallization kinetics of novel odd-odd polyamide 9 11

A study on isothermal and nonisothermal crystallization kinetics of odd-odd polyamide 9 11 was carried out by differential scanning calorimetry (DSC). The equilibrium melting temperature of polyamide 9 11 was determined to be 199.1 °C. The Avrami equation was adopted to describe isothermal crystallization of polyamide 9 11. Nonisothermal crystallization was analyzed using both the Avrami relation modified by Jeziorny and the equation suggested by Mo. The isothermal and nonisothermal crystallization activation energies of polyamide 9 11 were determined to be −310.9 and −269.0 kJ/mol using the Arrhenius equation and the Kissinger method, respectively.     

Nonisothermal crystallization and melting behavior of poly(3-hydroxybutyrate) and maleated poly(3-hydroxybutyrate)

Nonisothermal crystallization and melting behavior of poly(3-hydroxybutyrate) (PHB) and maleated PHB were investigated by differential scanning calorimetry using various cooling rates. The results show that the crystallization behavior of maleated PHB from the melt greatly depends on cooling rates and its degree of grafting. With the increase in cooling rate, the crystallization process for PHB and maleated PHB begins at lower temperature. For maleated PHB, the introduction of maleic anhydride group hinders its crystallization, causing crystallization and nucleation rates to decrease, and crystallite size distribution becomes wider. The Avrami analysis, modified by Jeziorny, was used to describe the nonisothermal crystallization of PHB and maleated PHB. Double melting peaks for maleated PHB were observed, which was caused by recrystallization during the heating process.     

Simulations of polymer crystallization under high pressure

High pressure crystallization of polypropylene was studied by means of PVT measurements and computer simulations. The isothermal crystallization behaviour were described by using a model which takes into account the effect of pressure on the temperature dependence of nucleation rate and linear growth rate. The agreement between the simulation and the experiments was seen in the tendency that the crystallization was accelerated by the high pressure. The non-isothermal crystallization behavior was also simulated by applying a generalized Avrami equation. The simulation curves well reproduced the experimental values below relative crystallinity 0.5 and below 100 MPa.