FROM CRYSTALLINE BLOCK SLIPS TO DOMINANCE OF NETWORK STRETCHING——MECHANISMS OF TENSILE DEFORMATION IN SEMI-CRYSTALLINE POLYMERS

The mechanism of tensile deformation in semi-crystalline polymers was studied based on true stress-strain curvesobtained with the aid of a video-controlled tensile set-up. The deformation is affected by both the crystalline and theamorphous phases. However, the relative weights of the two portions change with the deformation stage. At lowdeformations the coupling and coarse slips of the crystalline blocks dominate the mechanical properties, which allows thesystem to maintain a homogeneous strain distribution in the sample. As the stretching increases, at a critical strain the forcegenerated from entangled fluid portions reaches a critical value to destroy the crystallites. The dominant deformationmechanism then changes into a disaggregation - recrystallization process.

Dynamic Fracture of a Semi-Crystalline Bio-Based Polymer Pipe: Effect of Temperature

The influence of temperature on the resistance to rapid crack propagation of a semi-crystalline bio-based polymer was studied. The experimental results described in this study allow to initiate a first discussion on the role of viscosity and its link with the fracture behaviour and a heterogeneous microstructure such as the semi-crysalline polymer. Dynamic fracture tests on pipes were carried out. It would appear that a temperature decrease of approximately 40℃ relative to ambient has no significant influence on the average crack propagation velocity (≈0.6cR), fracture energy and surface roughness. On the contrary, crack propagation paths seem to vary with temperature. The difference in fracture behaviour between the amorphous and crystalline phase varies significantly as a function of temperature. The difference between the initiation resistance and the rapid propagation also varies. This difference seems to be significantly reduced by lowering the temperature. The mechanisms of cavitation damage and plastic flow are increasingly limited by the decrease in temperature (and therefore in macromolecular mobility). Crack propagation in the pipe is more extensive and therefore more critical. This is emphasised in particular by the probability of the material to be macro-branched as the temperature decreases.

Fundamental Mechanism of Slow Crack Growth in Semi-Crystalline Polymers under a Constant Load

The purpose is to quantitatively present in a single equation all the factors that affect the failure time by Slow Crack Growth (SCG) in a semi-crystalline polymer (SCP) under a constant load. The fundamental mechanism of fracture is displayed at the molecular level. The rate of fracturing is determined by the Eyring theory of thermal activation. The resulting equation includes the important molecular properties of therein, the length and density of the tie molecules. The underlying microfracture process is the unfolding of the chains in the crystal under the action of the tie molecules.

Fabrication and Characterization of Semi-Crystalline and Amorphous Dielectric Polymer Films for Energy Storage

Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric film capacitors. Two prominent examples of polymer dielectrics Polyetherimide (PEI) and Poly (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) have been discussed. Polyetherimide (PEI) is an amorphous polymer recognized for its high-temperature capability, low dielectric loss and high dielectric strength. THV is a semi-crystalline polymer with high dielectric constant, high-temperature capability and charge-discharge efficiency. The primary focus of this paper is to introduce the reader to the fabrication procedures and characterization techniques used in research labs for processing of dielectric polymers. The fabrication and characterization process of both polymers has been discussed in detail to shed the light on experimental process in this area of research.

Semi-LC/MS技术快速定量分析黄芪样品中黄芪甲苷含量

为了测定黄芪中的黄芪甲苷含量,应用半高效液相色谱-质谱串联技术(Semi-LC/MS),以薯蓣皂苷为内标化合物,仅用一段色谱保护柱分离掉大部分干扰性成分,同时使目标化合物富集,采用Waters公司的多反应监测(MRM)扫描模式检测。结果表明:黄芪甲苷在2.85～57.0mg/L的范围内线性关系良好,稳定性和重复性实验RSD<3%,样品回收率达98.9%。Semi-LC/MS方法可以对黄芪样品中黄芪甲苷进行快速定量分析,是一种黄芪甲苷的简单、高效、灵敏的定量检测方法。

Decomposition Theorems for Semi-order Fuzzy Supermartingales and Submartingales

Based on semi - order fuzzy supermaringales andsubmartingales, the semi- order fuzzy supermartingaleand submartingale theory is developed. The main resultis to generalize the Doob decomposition and the Riesz de-composition theorems of standard martingale theory tosemi - order fuzzy supermaringales and submartingales.The structure of semi - order fuzzy supermaringales andsubmartingales and the conditions of that they has Doobdecomposition (resp. Riesz decomposition) are discussedin detail.

小分子药物在半结晶乙烯-醋酸乙烯酯共聚物(EVA)中的扩散机理:自由体积理论

Free volume theory was applied to the diffusion mechanism of drug through semi crystalline ethylene vinyl acetate (EVA) copolymer. According to free volume theory, drug diffused through semi crystalline EVA via vinyl acetate segments of the copolymer, and the dependence of D (D: diffusion coefficient of drug through EVA) on a (a :vinyl acetate content of copolymer; a <0.5) could be described as ln (D)=A1-A2/a(A1, A 2:constant). This was demonstrated by experimental data from several references.

氮化硼、贝壳粉对聚乳酸材料结晶性能与导热性能的影响

以聚乳酸(PLA)为原料,选用氮化硼(boron nitride,BN)与贝壳粉作为提高PLA导热性能的功能粉体,采用熔融共混的方法制备具有高导热性能的BN/PLA和贝壳粉/PLA复合材料,研究功能粉体质量分数为0.5%、1.0%、1.5%时复合材料的结晶性能与导热性能的变化。利用差示扫描量热仪(DSC)分析了复合材料的结晶度和在不同结晶条件下的半结晶时间(t_(1/2));通过万能拉伸机测试复合材料的力学性能;通过扫描电子显微镜观察拉伸断面的形貌特征;使用导热系数测试仪测试添加不同质量分数无机粉体的复合材料的导热系数。结果表明:在加入BN与贝壳粉后,试样的结晶度分别提高至18.8%和15.3%;在温度为105℃的条件下,添加质量分数为1.5%的BN与贝壳粉分别能使BN/PLA和贝壳粉/PLA的t_(1/2)降低到0.33和0.39 min;随着功能粉体质量分数的增加,复合材料的导热系数逐渐上升,并且相对于单一功能粉体,BN与贝壳粉的复配粉体对PLA导热性能的提高效果更加显著,由0.177 W/(m·K)最高升至0.319 W/(m·K)。研究结果为后续制备凉感纤维提供参考。

用于芯片工厂的模块化高频UPS的配电拓扑分析

本文论述了用于极高可靠性供电要求的场合如芯片工厂的配电架构改良,单独内燃机驱动的柴油发电机组(下文简称柴发)作为后备电源进行供电保障优化为结合储能以及不间断电源(Uninterrupted Power Supply,下文简称UPS)相组合的供电保障,UPS的接线拓扑分析以及采用预充磁装置对优化的拓扑进行进一步改良。

Self-recoverable semi-crystalline hydrogels with thermomechanics and shape memory performance

Stimuli-responsive hydrogels have become one of the most popular artificial soft materials due to their excellent adaption to complex environments. Thermoresponsive hydrogels triggered by temperature change can be efficiently utilized in many applications. However, these thermoresponsive hydrogels mostly cannot recover their mechanical states under large strain during the process. Herein, we utilize the heterogeneous comb-type polymer network with semicrystalline hydrophobic side chains to design self-recovery semi-crystalline hydrogels. Based on hydrophilic/hydrophobic cooperative complementary interaction and heterogeneous polymer network, hydrogels can be endowed with excellent thermosensitive properties and mechanical performance. The hydrogels exhibit high compressive strength(7.57 MPa) and compressive modulus(1.76 MPa) due to the semi-crystalline domains formed by association of the hydrophobic poly(ε-caprolactone) PCL. The melting-crystalline transition of PCL and elastic polymer network provide the hydrogels excellent thermomechanical performance and self-recovery property. Furthermore, the hydrogels exhibit shape memory behavior, which can be realized by simple process and smart surface patterning. With these excellent properties, our hydrogels can be applied in sensors, flexible devices and scaffolds for tissue engineering.

聚吡咯-聚酯透明导电复合膜的研究(Ⅱ)电导率及其与温度的关系

作者在以前工作的基础上,对聚吡咯-聚酯透明导电复合膜的电导率及其与温度的关系进行了实验研究,应用渗流理论解释了复合膜的导电特性。实验结果表明,复合膜与非晶态半导体具有相同的电导率-温度变化规律。

STUDIES ON THE REGULAR COPOLYMERS OF POLY (1, 4-PHENYLENETEREPHTHALAMIDE)

Two types of the regular copolymer of poly (1, 4-phenyleneterephthalamide) were synthesized by the low temperature solution polycondensation in NMP-CaCl_2 solvent system, using the piperazine or 2,5-dimethylpiperazine as the third components introduced in the main chain of poly (1, 4-phenyleneterephthalamide). The properties of copolymers were characterized by IR, SEM, X-RAY diffraction, polarizing microscopy, TGA and solubilities.Experimental results showed that the copolymers had good solubility and thermal stability, the concentrated sulfuric acid (～98% ) solution of regular PPTA copolymers had liquid crystalline proper-

First-principles study of the co-effect of carbon doping and oxygen vacancies in ZnO photocatalyst

Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application,C-doping or oxygen vacancy(Vo)as a single defect in ZnO still has limitations for photocatalytic activity.Meanwhile,the influence of co-existence of various defects in ZnO still lacks sufficient studies.Therefore,we investigate the photocatalytic properties of ZnOx C0.0625(x=0.9375,0.875,0.8125),confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO.To clarify the underlying mechanism of co-existence of various defects in ZnO,we perform systematically the electronic properties calculations using density functional theory.It is found that the coeffect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO.Moreover,the impact of the effective masses of ZnO_(x)C_(0.0625)(x=0.9375,0.875,0.8125)is also taken into account.In comparison with heavy Vo concentrations,the light Vo concentration(x=0.875)as the optimal component together with C-doping in ZnO,can significantly improve the visible-light absorption and benefit photocatalytic activity.

STRUCTURE EVOLUTION OF POLYMER CHAINS FOR NECKING FORMATION IN HIGH-SPEED FIBER SPINNING PROCESS

Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions, The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process.

退火处理对柔性压电材料聚偏氟乙烯基电介质的压电性能影响研究

本文从聚偏氟乙烯基聚合物压电效应的晶体结构基础出发,研究不同退火温度(60~160℃)对薄膜样品表面结晶形貌、结晶尺寸、结晶度,以及关键介电参数包括极化响应曲线和压电系数的影响规律。结果表明:在60~140℃范围内,随着退火温度升高,样品结晶尺寸增大、结晶度提高,从而在极化曲线中表现出更高的剩余极化强度和滞回度,同时压电系数随退火温度升高从11 pC/N增大至27 pC/N。而当退火温度达到160℃时,样品表面出现裂痕缺陷,极化过程较容易发生击穿,且压电系数分散性较大。

氨基酸/脲醛缓释肥的制备及性能研究

【目的】开发一种具有多种养分、氮缓释性能优异、工艺简单、半互穿网络结构的缓释肥。【方法】利用溶液聚合配合原位挤出技术,将聚合过程和加工过程合二为一。以氨基酸原粉(AARP)和硫酸亚铁(FeSO4)为原料,将AARP和AARPFe与脲醛(UF)大分子链进行复合,形成具有半互穿网络结构的缓释肥(AARP-UF和AARPFe-UF)。通过红外光谱、X射线衍射和热重对缓释肥结构进行表征分析,扫描电镜(SEM)观察其表面形貌,测定其压缩强度及在静水及土壤中的氮养分释放率,研究添加AARP和AARPFe对其缓释性能的影响,并分析性能提高原因。【结果】UF、AARP-UF和AARPFe-UF 3种缓释肥的结晶度分别为67.9%、59.2%和57.4%,压缩强度分别为1.64、3.01、4.06MPa,在静水中的初期氮释放率分别为24.8%、18.6%和15.1%,处理90 d后土壤中氮累计释放率分别为55.9%、51.4%和46.3%。AARP和AARPFe的加入破坏了UF分子链晶体结构,形成氢键相互作用,使缓释肥结晶度降低,压缩强度提高,氮缓释性能得到明显改善。综合各项结果可知,缓释肥AARPFe-UF效果更佳。【结论】制备的新型缓释肥解决了UF初期氮释放率高的问题,避免了资源浪费,原料绿色、环保,综合性能优异,有利于工业化生产。AARP中含有天然营养物质,具有生态效应,可促进可持续农业体系发展。

An Ultrastable π-π Stacked Porous Organic Molecular Framework as a Crystalline Sponge for Rapid Molecular Structure Determination

The crystalline sponge method is a pragmatic and promising strategy for molecular structure determination.However,the dominant metal-organic framework crystal sponge platforms always face poor chemical stability,especially solvent instability,hampering their application in a vaster domain.Herein,we report an ultrastable π-π stacked porous organic molecular framework which exhibits permanent porosity,high thermal stability,and good chemical resistance.It can efficiently implement an approach to molecular structure determination via a single-crystal-to-single-crystal transformation.This is the first example utilizing π-π stacked porous organic molecular framework as“crystalline sponge”to determine a wide variety of guests,ranging from hydrophilic to hydrophobic,and from aliphatic to aromatic,which complements the crystalline sponges based on the famous metal-organic frameworks.More importantly,it can achieve rapid structure determination of small molecules within 3 h.

不同品种马铃薯淀粉的结构

为研究不同品种马铃薯淀粉的结构特征,采用小角X射线散射仪、偏光显微镜、X射线衍射仪及凝胶渗透色谱-多角度激光光散射联用技术系统分析了10种马铃薯淀粉的半结晶层结构、结晶形态、直链淀粉含量、相对分子质量和分子构象.结果表明:10种马铃薯淀粉颗粒的半结晶层结构存在差异,陇3的半结晶层厚度最小,其双螺旋结构排列最为有序,青2和青6的半结晶层厚度最大;10种马铃薯淀粉颗粒均为多晶体系,其结晶形态均为B型结构,但结晶度不同;10种马铃薯淀粉的直链淀粉含量不同,费乌瑞它、青5、青8的重均分子质量相对较大,除青5在二甲基亚砜中的构象为无规则卷曲外,其余均为球型.上述不同层次结构的差异为加工专用马铃薯淀粉的开发提供了基础数据.

新型UV固化粉末涂料的研制

合成了无定型、半晶型两种不同结构的不饱和聚酯树脂,由此配制成可紫外光固化的双组分粉末涂料。研究了聚酯树脂结构及树脂配比对涂料固化速度及涂膜附着力、抗冲击、硬度和光泽等性能的影响。结果表明,涂料配方中加入半晶型不饱和聚酯树脂,涂膜的抗冲性能和附着力明显提高,固化后的涂膜综合性能良好。

半芳香共聚尼龙6T／6的合成与结晶性能研究

通过溶液共聚的方法制备了半芳香共聚尼龙6T/6,并系统研究了共聚单体配比、共聚反应温度、时间等工艺因素对共聚物熔点、特性黏数和结晶性能的影响规律。