多壁碳纳米管/聚丙烯复合材料的晶型及非等温结晶动力学

采用熔融共混法制备了多壁碳纳米管/聚丙烯(MWNT/PP)复合材料,利用X射线衍射法(XRD)、差示扫描量热法(DSC)分别研究了纯聚丙烯(PP)及MWNT/PP复合材料的晶型和非等温结晶动力学行为,并运用Mo法研究了纯PP及MWNT/PP复合材料的非等温结晶动力学行为。结果表明,多壁碳纳米管(MWNT)的加入使PP发生了由β晶型向α晶型的转变。MWNT在结晶过程中具有异相成核效应,提高了PP的结晶温度和结晶速率。MWNT/PP复合材料的结晶活化能均明显高于纯PP。MWNT的加入使PP在单位时间内达到一定结晶度所需的降温速率减小。     

高填充可降解淀粉基聚烯烃材料的制备及其堆肥降解

制备了高填充的聚乙烯（PE）-淀粉-碳酸钙（CaCO3）三元复合材料,根据ASTM D6400标准对该材料进行了堆肥降解。采用熔体流动速率（MFI）、差示扫描量热分析（DSC）、扫描电镜分析（SEM）等方法研究了该复合材料的堆肥降解行为。结果表明：堆肥降解过程中,熔体流动速率（MFI）在堆肥1个月左右出现极小值;降解过...     

磷酸对无机钛硅原料体系合成TS-1晶化速率的促进作用

考察了磷酸对无机钛硅原料体系合成TS-1晶化速率的影响．结果表明，磷酸的单独引入，可以将晶化时间由原来的120h左右缩短到90h左右．当晶种与磷酸共同作用时，晶化时间可以缩短到60h．同时磷酸的加入对TS-1的晶粒尺寸及晶型也有影响．在既不加入晶种也不加入无机酸时，TS-1晶体在9μm左右；加入晶种后约为6μm；加入无机酸后约18μm左右，且晶体两端呈尖形；当无机酸与晶种同时作用时约为13μm，晶型与单独加入磷酸的样品相同．另一方面，加入磷酸TS-1原粉的收率可以提高到85％左右．这表明磷酸的加入促进了TS-1晶体的生长，提高了晶化速率，缩短了晶化时间．     

Al-4.5Cu和Mullite增强Al-4.5Cu复合材料时效析出行为的DSC研究

用差示扫描量热法（DSC）对Al-4.5Cu合金和莫来石（Mullite)短纤维增强Al-4.5Cu复合材料的时效析出行为进行了研究；结果表明Al-4.5Cu合金和Mullite增强Al-4.5Cu复合材料固溶淬火试样的DSC扫描曲线存在较大不同，溶质原子富集区（GP）形成和溶解的信息在基体合金的DSC曲线上清晰可见，但在复合材料的DSC曲线上则很难确认，表明纤维推延或抑制了GP区的形成；中间沉淀析出相θ″和θ′的析出过程由于纤维的引入而得到明显加快，峰值温度降低，活化能减小，时效析出过程加快；但是，扫描参数选择不当时，容易对析出相的析出过程产生错误判断，应引起重视。     

钇对Nd-Fe-Al-Ni非晶合金热稳定性与晶化行为的影响

采用差示扫描量热法（DSC）、X射线衍射（XRD）和透射电镜（TEM）研究了Y对Nd-Fe-Al-Ni非晶合金热稳定性和晶化行为的影响。结果表明,淬火态的Nd60Fe20Al10Ni10-xYx（x=0,2）合金基本为非晶组织同时还含有少量的淬态相,Y的加入抑制了淬态相的析出。加入Y后,非晶合金的晶化开始温度和晶化峰值温度都向高温方向移动,证明其热稳定性提高。Y的加入改变了合金的晶化方式和最终晶化产物,使非晶基体中析出的晶化相更加弥散圆整细小。并且Y具有在化学上钝化氧杂质的作用,从而抑制了氧的有害作用。利用Kissinger方程获得了Nd60Fe20Al10Ni8Y2非晶合金的晶化开始和晶化峰值激活能分别为1.21和1.16 eV。     

多元Gd（n）-Ni-Al合金系中非晶形成能力的成分依赖性研究

采用水冷铜模吸铸法制备了Gd（Tb）-Ni-Al合金系样品。利用x射线衍射仪（XRD）,示差扫描量热仪（DSC）和差热分析仪（DTA）分别检测了合金的结构,玻璃转变,晶化和合金的熔化行为。用γ参数来表征Gd基大块金属玻璃的非晶形成能力。结果表明,多元Gd基合金的非晶形成能力对Tb有较大的依赖性,15％Tb替换Gd57Ni20Al23合金中的Gd元素提高了Gd系合金的非晶形成能力,并应用等效电负性差（△x）和等效原子半径差（δ）讨论了该系列合金的本征非晶形成能力。     

纳米Ag/CNTs复合材料的制备、表征及对环三亚甲基三硝胺热分解的影响

采用银镜法和水热法制备了两种纳米Ag/CNTs(碳纳米管)复合材料, 利用傅里叶变换红外(FTIR)光谱、粉末X射线衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜及能量散射光谱仪(SEM-EDS)对复合物的物相、组成、形貌和结构进行分析表征, 并运用差示扫描量热法(DSC)研究了纳米Ag/CNTs 复合材料对环三亚甲基三硝胺(RDX)热分解特性的影响. 结果表明: 纳米Ag 以10-80 nm的不规则球形“粘附”于纳米CNTs 表面,分散较均匀, 水热法制得的复合物表面纳米Ag较大、且负载的Ag粒子较多; 纳米Ag/CNTs 复合材料的加入改变了RDX的热分解过程, 使原有占主导的液相分解变为二次的气相反应加剧, RDX主分解峰形发生了明显的改变; 纳米Ag/CNTs 复合材料对RDX热分解的催化主要表现为分解温度的降低.     

四乙基溴化铵-氟化物复合模板剂合成β沸石 Ⅲ.结晶动力学及其影响因素

 考察了用四乙基溴化铵－氟化钠复合模板剂合成β沸石的结晶动\r\n力学．结果表明：其晶化曲线为典型的S形曲线；成核活化能En＝65．\r\n79kJ／mol，生长活化能Ec＝91．49kJ／mol；与单纯的四乙基溴化铵模\r\n板剂体系相比，本体系成核诱导期较短，生长速率较快；n（NaF）／n\r\n（SiO2）值增大时，晶化诱导期缩短，成核速率加快，但氟化钠量过高\r\n时，成核速率反而降低，n（NaF）／n（SiO2）最佳值为0．10～0．17\r\n；较高的OH－／SiO2比有利于缩短晶化诱导期．     

聚碳酸酯/短切碳纤维/二苯砜磺酸钾复合材料的阻燃性能

采用熔融共混方法制备了聚碳酸酯/短切碳纤维/二苯砜磺酸钾（PC/sCF/KSS）复合材料,通过垂直燃烧（UL-94）、极限氧指数（LOI）和锥型量热测试研究了同时加入sCF和KSS对PC阻燃性能的影响。结果表明,当加入质量分数2%的sCF和质量分数0.1%的KSS时,PC/2sCF/0.1KSS复合材料的LOI较纯PC(27.2%)大幅提高,达到36.2%,UL-94等级达到V-0级。sCF和KSS在降低PC热释放和烟释放方面表现出协同效应。与纯PC相比,PC/2sCF/0.1KSS复合材料的峰值热释放速率（pHRR）降低59%,峰值烟释放速率（pSPR）降低57%,峰值CO释放速率（pCOP）降低63%,均优于单独加入sCF或KSS的样品。在燃烧过程中,sCF和KSS的同时加入在PC复合材料中发挥了优异的凝聚相阻燃作用。此外,PC/2sCF/0.1KSS复合材料的冲击强度、拉伸强度、断裂伸长率与纯PC相比变化不大,力学性能得到保持。     

聚丙烯/凹凸棒土纳米复合材料结晶形态和形貌研究

采用熔融共混的方法 ,制备聚丙烯 凹凸棒土纳米复合材料 .通过X射线衍射 (XRD)分析凹凸棒土在聚丙烯复合材料中晶面间距的变化以及对聚丙烯晶型的影响 ,结果表明凹凸棒土在复合材料中晶面间距没有变化 ;聚丙烯晶型没有发生变化但晶粒尺寸增加了 .用示差扫描量热法 (DSC)分析聚丙烯复合材料的结晶度的变化 ,发现凹凸棒土的加入使复合材料的结晶温度提高 ,结晶速率增大 ,结晶度增加 .用偏光显微镜(POM)观察凹凸棒土对聚丙烯球晶的影响 ,结果表明凹凸棒土的加入起到了成核剂的作用 ,使得聚丙烯球晶尺寸减小 ,当凹凸棒土的加入量到 10 %左右时 ,观察不到完整的球晶 .利用扫描电子显微镜 (SEM)和原子力显微镜 (AFM)观察凹凸棒土在聚丙烯中的分散 ,发现凹凸棒土在聚丙烯基体中分散比较均匀 ,但呈无序分布 .     

Enhanced Nucleation and Crystallization in PLA/CNT Composites via Disperse Orange 3 with Corresponding Improvement in Nanomechanical Properties

The potential for the material property improvement through the addition of carbon nanotubes (CNTs) in composite materials is often limited due to CNT agglomeration. In this work, Disperse Orange 3 (DO3) was investigated to determine its effectiveness in dispersing CNTs in a poly (lactic acid) (PLA) matrix. First, adsorption studies of DO3 onto CNTs were performed to determine the appropriate amount of DO3 to add so that the CNT surface will be nearly saturated with DO3 while limiting the excess DO3 dissolved in the polymer. The resultant improvements in the mechanical properties were determined via nanoindentation. Highly stable dispersion of CNTs in tetrahydrofuran with DO3 was observed 72 hours after sonication. Scanning electron microscopy confirmed that DO3‐functionalized CNTs were able to separate and disperse well inside of the PLA matrix. Addition of DO3 to the nanocomposite resulted in an increase in the glass transition temperature and crystallinity of the composite due to the more effective dispersion of the nanofiller which serves as a nucleation agent. The CNTs treated with DO3 also increased the elastic modulus and hardness of the composite compared to neat PLA and untreated PLA‐CNT composites. From this study, DO3 was demonstrated to be an effective dispersing agent in the solvent and the PLA matrix which allowed for enhanced crystallization and improved nanomechanical properties in the resultant composite.     

Polymorphism and transcrystallization of syndiotactic polystyrene composites filled with carbon nanotubes

Syndiotactic polystyrene (sPS) composites filled with well-dispersed multi-walled carbon nanotubes (CNTs) were readily prepared through a coagulation method. Fourier-transform infrared spectroscopy and wide-angle X-ray diffraction revealed the effect of CNTs on the polymorphism of sPS. When crystallized from the melted state, the formation of the β-form was always favored after CNT addition regardless of crystallization conditions (isothermal or non-isothermal). In the case where liquid nitrogen was used to quench the melt, the uncrystallized material that was not able to crystallize in the extremely short crystallization time crystallized in the α form upon subsequent cold crystallization. Regardless of the CNT content, the glass transition and equilibrium melting temperature of the sPS matrix were unchanged at ∼96 and 290 °C, respectively. With a gradual increase in CNT loading, the sPS crystallization rate initially increased but then reached a plateau value at high CNT concentrations because of the reduction in chain mobility. Moreover, the Avrami exponent was changed from 2.8 for samples at low CNT contents to 2.0 for samples with a CNT concentration above 0.1 wt.%, at which the rheological threshold was approached and a polymer-CNT hybrid network was formed. The enhanced crystallization kinetics was attributed to the high nucleating ability of CNTs to induce a transcrystalline layer (TCL) at its surface, as revealed by transmission electron microscopy. For composites with low levels of CNT, the growth of sPS spherulites in the bulk between CNTs prevailed. Provided that the CNT-related networks were developed, the two-dimensional growth of cylindrical TCL at the CNT surface became dominant and led to the expected Avrami exponent.     

The effect of heat treatment on water sorption in polylactide and polylactide composites via changes in glass‐transition temperature and crystallization kinetics

Water sorption into polylactide (PLA) and polylactide‐montmorillonite (PLLA‐MONT) composites containing 5 wt % of montmorillonite (MONT) under different heat treatment conditions was studied using the quartz crystal microbalance/heat conduction calorimetry (QCM/HCC) technique. Results showed that water sorption in neat polymer films and composite films increased with heat treatment temperature up to 120 °C. Differential scanning calorimetry was used to measure the glass‐transition temperature and isothermal crystallization kinetics of all samples. The mobility of the amorphous domain in all samples increased with heat treatment temperature, indicated by the decrease in glass‐transition temperature. PLA composites crystallized at a much faster rate than neat PLA did because MONT acted as a nucleating agent. Under the same heat treatment condition, water sorption in PLLA‐MONT composites was always higher than that in neat PLA due to the presence of the hydrophilic hydroxyl groups on the surface of MONT particles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Thermal analysis of mechanochemically activated glass

Thermal analysis (TG, DTG, DTA, DSC) has been used to study the influence of mechanochemical activation of glass making batch on its melting and obtained glass crystallization. It revealed, that long time (12 h) mechanical treatment accelerates the glass batch melting and also improving network homogeneity influence the internal structure of the obtained glass. Refinement of the glass, at the beginning reduces temperature and increases degree of crystallization as a result of nucleating action of the increasing surface area of grains. However long time activation lowers the crystallization ability of glass and increases crystallization temperature. This is attributed to the deformation of the structure surface layer and surface energy increase, hampering the crystals nuclei formation.     

Glass transition and enthalpy relaxation of ethylene glycol and its aqueous solution

Differential scanning calorimetry (DSC) and cryomicroscopy were employed to investigate the glass transition and enthalpy relaxation behaviors of ethylene glycol (EG) and its aqueous solution (50% EG) with different crystallization percent. Isothermal crystallization method was used in devitrification region to get different crystallinity after samples quenched below glass transition temperature. The DSC thermograms upon warming showed that the pure EG has a single glass transition, while the 50% EG solution has two if the solution crystallized partially. It is believed that the lower temperature transition represents the glass transition of bulk amorphous phase of EG aqueous solution glass state, while the higher one is related to ice inclusions, whose mobility is restricted by ice crystal. Cryomicroscopic observation indicated that the EG crystal has regular shape while the ice crystal in 50% EG aqueous solution glass matrix has no regular surface. Isothermal annealing experiments at temperatures lower than T_g were also conducted on these amorphous samples in DSC, and the results showed that both the two amorphous phases presented in 50% EG experience enthalpy relaxation. The relaxation process of restricted amorphous phase is more sensitive to annealing temperature.     

Influence of Moisture on the Glass Transition of A Spray-Dried Compound Using the Isosteptm Method

The interaction among moisture content, solvent loss and glass transition temperature is relevant for processing of spray-dried pharmaceuticals, since the glass transition temperature determines the application range of a compound. Conventional Differential Scanning Calorimetry (DSC) does usually not allow to separate glass transitions from common kinetic effects like evaporation or crystallization. Based on classical DSC methods, the IsoStep^TM method allows the independent determination of heat capacities and kinetic effects, and thus, the separation of kinetic effects from effects arising from heat capacity changes. This technique is used to separate glass transition and evaporation processes, and to find the relation between moisture content and glass transition temperature for a pharmaceutical sample based on a modified Gordon–Taylor equation. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Single Glass Fiber with Ultrathin Layer of Carbon Nanotube Networks Beneficial to In-Situ Monitoring of Polymer Properties in Composite Interphases

Electrophoretic deposition (EPD) is used to deposit multiwalled carbon nanotube networks (CNTs) onto electrically insulating glass fiber surfaces. We found that the thin networks on a single glass fiber surface exhibit semiconducting properties. This enables us to realize a single CNT-glass fiber as a probe with novel multifunctional capabilities for in-situ monitoring of various chemical/physical transitions, particularly in the interphase region between polymer and glass fiber. Because of the intimate interaction between CNTs and polymers in the vicinity of a glass fiber, our CNT probe can rapidly sense the local changes of fundamental polymer properties, such as glass transition, reaction activation energy, cross-linking reaction, and crystallization.     

Nanoparticle Dispersion and Glass Transition Behavior of Polyimide-grafted Silica Nanocomposites

How to control the spatial distribution of nanoparticles to meet different performance requirements is a constant challenge in the field of polymer nanocomposites.Current studies have been focused on the flexible polymer chain systems.In this study,the rigid polyimide(PI) chain grafted silica particles with different grafting chain lengths and grafting densities were prepared by "grafting to" method,and the influence of polymerization degree of grafted chains(N),matrix chains(P),and grafting density(a) on the spatial distribution of nanoparticles in the PI matrix was explored.The glass transition temperature(Tg) of PI composites was systematically investigated as well.The results show that silica particles are well dispersed in polyamic acid composite systems,while aggregation and small clusters appear in PI nanocomposites after thermal imidization.Besides,the particle size has no impact on the spatial distribution of nanoparticles.When σ·N0.5<<(N/P)2,the grafted and matrix chains interpenetrate,and the frictional resistance of the segment increases,resulting in restricted relaxation kinetics and Tg increase of the PI composite system.In addition,smaller particle size and longer grafted chains are beneficial to improving Tg of composites These results are all propitious to complete the microstructure control theory of nanocomposites and make a theoretical foundation for the high performance and multi-function of PI nanocomposites.     

Glass transition kinetics of some Se-Te-Ag chalcogenide glasses

Summary The present paper reports the Differential Scanning Calorimetric (DSC) study of some Ag doped Se-Te chalcogenide glasses. DSC runs were taken at different heating rates. Well-defined endothermic and exothermic peaks were obtained at glass transition and crystallization temperatures. The variation of glass transition temperature T_gwith Ag concentration has been studied. It has been found that T_gdecreases with increase in Ag concentration. The heating rate dependence of T_gis used to evaluate the activation energy of glass transition (DE_t). The value of<span style='font-size:10.0pt; font-family:"SymbolProp BT";mso-bidi-font-family:"SymbolProp BT"'>DE_thas been found to increase with increase in Ag concentration followed by nearly constant value at higher concentrations of Ag.     

Aging and cold crystallization of melt‐extruded poly(trimethylene terephthalate) films

We analyzed the thermal crystallization, glass‐transition behavior, and mechanical properties of melt‐extruded poly(trimethylene terephthalate) (PTT) films to investigate their physical aging and annealing effects. The physical aging and annealing of PTT films had an influence on the glass‐transition temperature, recrystallization behavior, and mechanical properties. When samples were aged at an ambient temperature, the crystallization temperature decreased largely within 5 h, the heat of crystallization increased, and the breaking stress and breaking elongation increased. The glass‐transition temperature of annealed samples, which was obtained from differential scanning calorimetry and dynamic mechanical measurements, increased with increasing annealing temperature below 80 °C but decreased above that temperature. In addition, the glass‐transition temperature and modulus of annealed samples were largely affected by the annealing time; in particular, they increased sharply within 1 h on annealing at 50 °C. Consequently, the change in the glass‐transition temperature on annealing was ascribed to the fact that the molecular constraint due to recrystallization and the mobility of rigid amorphous PTT chains competed with each other, being dependent on the annealing temperature. The mechanical properties of aged samples were closely related to their cold‐crystallization behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1920–1927, 2001