热塑性聚合物复合材料蠕变性能的综述（英文）

热塑性聚合物复合材料(TPCs)由于其力学性能优异、产量巨大,并具有价格优势,已被作为重要的结构材料得到了广泛的应用。然而,由于聚合物的粘弹本性,其不可避免地会在外力的作用下产生随着时间延长而增加的形变,即蠕变。这种作用将对材料造成永久形变以及不可恢复的破坏,从而限制材料的应用。本文通过对TPCs蠕变的研究综述,详细探讨了TPCs蠕变的机理特征,分析了各类因素(诸如分子结构、填料、应力、温度等)对TPCs蠕变作用的影响规律。在此基础上,简明扼要的分析并提出了有助于获得抗蠕变性能优异的TPCs的方法。     

ATRP法合成含氟丙烯酸酯类聚合物的研究进展

含氟丙烯酸酯聚合物由于氟原子的改性作用而具有优异的表面特性,不仅稳定,具有很好的耐氧化和耐腐蚀性,而且具有较好的耐水、耐油及耐污性,可望在新材料的开发、理论研究和实际应用等方面获得广泛的应用.而原子转移自由基聚合(ATRP)又可为分子设计和合成提供很有效的途径,利用这种聚合可以获得预期结构和性能的含氟嵌段聚合物材料,充分发挥含氟元素的改性作用.本文综述了ATRP在丙烯酸氟烷基酯聚合物合成方面的应用,并介绍了国内外在此领域的研究状况.     

可交联含氟聚醚醚酮的合成

聚醚醚酮 (PEEK)是一种耐热等级高、耐化学药品、耐辐射并有优异的电性能及机械性能的特种工程塑料 .由于其综合性能优异 ,PEEK在航空航天、通信、电子和机械化工等领域获得成功应用 [1] .含氟芳香聚合物以其独特的性能而成为低介电常数微电子和低损耗光波导器件极具潜力的材料 [2 ] .聚合物良好的溶解性虽对光电集成电路的加工十分重要 ,但也要满足多层化操作过程 ,还要考虑器件成型后的抗化学药品性 .因而 ,在聚合物中引入可交联组分是必要和可行的方法 .另外 ,交联后的聚合物将有更高的玻璃化转变温度 (Tg)、更好的尺寸稳定性和防开…     

共轭聚合物在生物传感与生物医药领域的研究进展

共扼聚合物(CPs)是一类具有离域π-π共轭骨架的高分子材料,在生物医药领域显示了广阔的应用前景.相比于传统的荧光小分子材料,共轭聚合物由于具有优异的光捕获能力、高的单线态氧产率及良好的生物相容性等优势受到了广泛关注.本文从共轭聚合物的结构设计和性能调控的角度出发,重点总结了本课题组近十年来在共轭聚合物的设计合成及其在...     

间歇加力聚合物温度形变曲线测定仪的研制

介绍了一种完全由计算机进行参数设定和数据采集的聚合物温度形变曲线测定仪，可以适用于教学或科研中聚甲基丙烯酸甲酯等聚合物材料线性及非线性膨胀行为的分析，玻璃化转变温度、粘流温度等特征温度的测定，以及玻璃化转变等过程中分子运动行为分析及相关参数测定。所研制仪器以间歇加力的方式，测定加力周期内聚合物材料形变随加力过程的变化，检测到加力与不加力状态下材料形变情况，借以消除常规持续加力方式测定时所带来的仪器热变形、材料蠕变等误差，达到对相关性能更准确测定和分析的目的。该仪器可以通过调整升温速率、间歇加力周期参数、间歇加力大小等参数设置，获得对各种聚合物材料的相对普适性。     

聚合物磷光材料的研究进展北大核心CSCD

金属配合物磷光材料因为其能同时利用单线态激子和三线态激子,引起了人们广泛关注。聚合物磷光材料(polymer phosphorescent materials,PPMs)同时具备小分子金属配合物的良好发光特性和高分子的优异物理性能,如容易挠曲、可溶液加工和良好的成膜性。本文综述了近年来聚合物磷光材料的研究进展,总结了聚合物磷光材料的合成方法及其在有机电致发光器件(OLED)方面的应用。最后从电磷光发光聚合物的分子结构设计出发,在电磷光发光聚合物领域业已取得进展的基础上,分析了电磷光发光聚合物在电致发光领域应用中存在的一些问题,并展望了电磷光聚合物今后的发展方向。     

聚合物磷光材料的研究进展

金属配合物磷光材料因为其能同时利用单线态激子和三线态激子,引起了人们广泛关注。聚合物磷光材料(polymer phosphorescent materials,PPMs)同时具备小分子金属配合物的良好发光特性和高分子的优异物理性能,如容易挠曲、可溶液加工和良好的成膜性。本文综述了近年来聚合物磷光材料的研究进展,总结了聚合物磷光材料的合成方法及其在有机电致发光器件(OLED)方面的应用。最后从电磷光发光聚合物的分子结构设计出发,在电磷光发光聚合物领域业已取得进展的基础上,分析了电磷光发光聚合物在电致发光领域应用中存在的一些问题,并展望了电磷光聚合物今后的发展方向。     

共轭聚合物生物电子体系研究进展

共轭聚合物类的有机共轭分子由于其特殊的电子离域效应,具有优异的光电性能.另外该类材料骨架结构丰富、能带可调、易于修饰与制备,使得这类材料除了在发光二极管、场效应晶体管和光伏电池等方面有广泛的研究和应用之外,在生物成像、生物传感、疾病诊断和治疗中也发挥了重要作用.本文综述了近年来基于水溶性共轭聚合物的生物电子体系构建和应...     

基于异靛青的聚合物场效应晶体管材料研究进展

20世纪80年代以来,有机电子学领域的研究取得了很大进展.有机半导体材料凭借其成本低、质量轻、柔性好、易修饰、可大面积溶液加工等特点吸引了学术界以及工业界的极大关注.其中,第三代有机共轭聚合物,给-受体(Donor-Acceptor,简称D-A)共轭聚合物材料的发展尤为迅速.最近,以异靛青(Isoindigo,IID)类结构作为受体片段的D-A共轭聚合物被发现具有优异的性能,特别是在聚合物场效应晶体管器件中获得了最高3.62 cm~2·V~(-1)·s~(-1)的空穴迁移率,其衍生物获得14.4 cm~2·V~(-1)·s~(-1)的空穴迁移率,具有良好的应用前景.综述了近年来国内外关于异靛青结构在聚合物场效应晶体管材料中的应用,对其分子结构设计、器件制备以及构效关系做了详细介绍,希望为今后异靛青类化合物的应用拓展提供指导思路.     

碳量子点上转换材料的制备及其应用研究进展

碳量子点(CQD)具有化学惰性,生物相容性和低毒性等优势,可能在能源、生物医药等领域得到广泛的应用. CQD可通过表面被聚合物(例如PEG)钝化而表现出很强的光致发光特性.在生物成像,疾病检测和药物输送中使用表面钝化后的功能化生物分子更为有效.并且碳材料由于其优异的电化学性能还展现出在催化、电子器件等许多领域广泛的应用前景.我们将对近年来碳量子点发光材料的研究进行总结,并讨论碳量子点在能源、环境和其他一些领域的应用.     

Polymer crystallinity and its effect on the non-linear bending creep rate for a polyphenylene sulphide thermoplastic composite

Recent developments have led to the introduction of advanced thermoplastic composites such as Polyphenylene Sulphide (PPS), which can be used structurally at higher temperatures. Because of its thermoplastic nature, it can also be hot worked by bringing the working temperature considerably above the glass transition temperature. However, such annealing processes also affect its degree of crystallinity, which in turn affect the properties of the material. This paper reports on the effect of matrix crystallinity on the rate of creep deformation in three point bending of some reinforced PPS composites. This work was based on a non-linear approach based on a Power law creep model creep deformation analysis. The effect of annealing on the non-linear creep deformation of the PPS composite specimens has been analysed using a Power Law creep model. Results indicate that the creep deformation for both 20 and 40% reinforced samples were relatively similar despite the difference in the amount of fibre reinforcement. In contrast, the value of the creep component decreased exponentially with the % crystallinity. for both 20 and 40%, reinforced samples.     

Interaction between creep,oxidation and microporosity in reaction-bonded silicon nitride

Kinetic studies have been performed on primary and secondary (minimal) creep of reaction-bonded silicon nitride in 4-pt-bending tests up to 1500°C. The creep deformation depends strongly on the extent of internal oxidation. In spite of the very marked dependence of the creep rate on material and pretreatment parameters, the stress exponents (n = 1.7–1.8) and activation energies (360–390 kJ/mole) are hardly influenced, suggesting similar creep mechanism. Creep deformation is provided by relative motion and separation of grain boundaries. Oxidation and deformation lead to remarkable changes of the pore size distribution; the creep processes are accompanied by deformation of the pores. The creep rupture strain is very limited in highly creep resistant materials and vice versa. Methods for the determination of oxidation products and oxide profiles along sample cross section have been developed and the chemical changes which the material can undergo during creep are outlined.     

Organic soft crystals exhibiting spontaneously reversible mechano-responsive luminescence

Mechano-responsive luminescence, or mechanochromic luminescence (MCL), is a type of luminescence that can be reversibly controlled by the addition of mechanical stimuli. Organic materials exhibiting MCL have been an ongoing area of development since the early 2000s, and the number of reports into such materials has been steadily increasing. While the majority of MCL systems rely on the brittle nature of organic crystalline solids, there is a growing interest in "flexible" organic crystals that exhibit mechanical bending or shape deformation owing to their elasticity/plasticity. Such non-destructive deformed crystals may exhibit a new type of MCL that can be controlled by the magnitude of the force stress. In this review, we describe MCL systems capable of the spontaneous recovery of changes in their luminescent properties in response to the loading/unloading of mechanical stress. We particularly focus on the MCL of flexible crystals based on the density gradient of molecular packing (i.e., elastic and plastic crystals) and an emerging system known as "superelastochromism,” which is based on spontaneously reversible crystal polymorphism. This emerging research area has the potential to play an important role in the promotion of next-generation soft crystals.     

Molecular Dynamics Simulation of High-Temperature Creep Behavior of Nickel Polycrystalline Nanopillars

As Nickel (Ni) is the base of important Ni-based superalloys for high-temperature applications, it is important to determine the creep behavior of its nano-polycrystals. The nano-tensile properties and creep behavior of nickel polycrystalline nanopillars are investigated employing molecular dynamics simulations under different temperatures, stresses, and grain sizes. The mechanisms behind the creep behavior are analyzed in detail by calculating the stress exponents, grain boundary exponents, and activation energies. The novel results in this work are summarized in a deformation mechanism map and are in good agreement with Ashby’s experimental results for pure Ni. Through the deformation diagram, dislocation creep dominates the creep process when applying a high stress, while grain boundary sliding prevails at lower stress levels. These two mechanisms could also be coupled together for a low-stress but a high-temperature creep simulation. In this work, the dislocation creep is clearly observed and discussed in detail. Through analyzing the activation energies, vacancy diffusion begins to play an important role in enhancing the grain boundary creep in the creep process when the temperature is above 1000 K.     

A test procedure for separating viscous recovery and accumulated unrecoverable deformation of polymer under cyclic loading

After uniaxial tension and creep tests, asymmetric stress cycle tests have been performed on two polycarbonate (PC) materials with different molecular weights at room temperature. The effects of stress level (mean stress and stress amplitude) and time-dependent factors (stress rate and peak hold time) on ratcheting were studied. To separate the contributions of viscous recovery and accumulated unrecoverable deformation, a new test procedure has been proposed and performed on polycarbonate. The results demonstrate that the proposed test procedure is suitable for separating the viscous recovery and accumulated unrecoverable deformation. The study clearly shows that, for PC, both the viscous recovery and the accumulated unrecoverable deformation cannot be neglected for cyclic loading; previous viscous deformation has significant influence on the following cyclic accumulated deformation.     

金属硫化物在可充电电池中的研究进展

低成本、长寿命、高安全性、高性能且易于大规模生产的锂/钠离子电池已被证实为重要的二次储能设备。 电极材料对锂/钠电池性能与循环寿命影响极大,金属硫化物由于具有高比容量和低电势而极具潜力成为锂/钠离子电池负极材料。 在电化学循环过程中,由于金属硫化物容易产生穿梭效应和体积变化,从而电极材料结构被破坏,进一步导致电池容量衰退、稳定性降低。 本文总结了多种金属硫化物的微观结构调控策略,从三维空间构建到与其它材料的复合,增强了电极的导电性和减缓体积变化带来的负面影响,进而获得性能优异的金属硫化物负极材料。 通过对金属硫化物的结构与性能的讨论,对其研究前景进行了积极的展望。     

Viscoelastic characterization of polymers using instrumented indentation. I. Quasi‐static testing*

The use of instrumented indentation to characterize the mechanical response of polymeric materials was studied. A model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for the creep compliance and stress relaxation modulus for two glassy polymeric materials, epoxy and poly(methyl methacrylate), and two poly(dimethyl siloxane) (PDMS) elastomers. Results from bulk rheometry studies were used for comparison with the indentation stress relaxation results. For the two glassy polymers, the use of sharp pyramidal tips produced responses that were considerably more compliant (less stiff) than the rheometry values. Additional study of the deformation remaining in epoxy after indentation creep testing as a function of the creep hold time revealed that a large portion of the creep displacement measured was due to postyield flow. Indentation creep measurements of the epoxy with a rounded conical tip also produced nonlinear responses, but the creep compliance values appeared to approach linear viscoelastic values with decreasing creep force. Responses measured for the unfilled PDMS were mainly linear elastic, with the filled PDMS exhibiting some time‐dependent and slight nonlinear responses in both rheometry and indentation measurements. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1794–1811, 2005     

Tensile creep of thermoplastics: Time‐strain superposition of non‐iso free‐volume data

The dimensional stability of thermoplastics is characterized by their tensile compliance D(t,σ,T) as a function of time t, stress σ, and temperature T. Creep retardation times are controlled by the free volume available for underlying molecular (segmental) motions. Tensile deformation of polymeric materials, whose Poisson ratio is smaller than 0.5, is accompanied by volume dilatation that can be identified with an increase in available free volume. Consequently, a steady increase in strain with time during tensile creep experiments accounts for shortening of the retardation times. The superposition of as‐received tensile compliance curves is difficult because any point of a curve requires a shift factor along the time axis that differs from those of other points. In this article, tensile creep at a constant stress and temperature is viewed as a non‐iso free‐volume process. A procedure is proposed to transform as‐received data to a pseudo‐iso free‐volume state that eliminates this deficiency and permits construction of a generalized compliance curve for the pseudo‐iso free‐volume state. This curve can be used for calculation of real‐time‐dependent compliance for any selected stress in the range of reversible deformations. As the superposed curve can be generated with several short‐term creep tests (e.g., 100 min) for a series of stresses, the proposed procedure saves experimental time. The effects of physical aging on tensile compliance (observed previously by other researchers) are interpreted in terms of the proposed approach in appendix A . © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 736–748, 2003     

Reversible plasticity shape memory polymers: Key factors and applications

Reversible plasticity shape memory (RPSM) polymers have been emerging as new smart materials with distinctions compared with conventional SMPs, such as easier shaping programming, stronger recovery stress, and higher recovery strain. For purposeful control of the structure, and therefore the physical and mechanical properties, a full understanding of the deformation habits of such materials under different conditions is essential. This perspective provides the context as to how the deformation temperature and fixing conditions influence the fixity and recovery behavior of RPSM polymers and what are the optimized conditions for RPSM. We hope that this will afford useful information for fabricating RPSM polymers with better memory properties and promote the technical development of new design methods of such materials for advanced applications © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1295–1299     

Creep relaxation and stress relaxation of PS-HI/SEBS blends

For the selection of the polymer materials and polymer blends for various fields of applications the stability of material under constant deformation and constant load are very important. In this paper, the copolymers high-impact polystyrene, PS-HI, styrene-ethylene/buthylene-styrene block copolymer, SEBS, and their blends PS-HI/SEBS were investigated. The investigations were done by DMA analysis. The secondary viscoelastic functions, creep, creep modulus, stress and flexural relaxation modulus were investigated in creep and stress relaxation experiment at temperatures 25, 35, 45, 55 and 65°C during 1 h. The master curves were created by time-temperature correspondence principle, TTC. The correlation of the secondary viscoelastic functions with time, temperature and content of the hard, PS, phase was discussed.