聚氨酯改性E-51/MeTHPA的工艺与性能

本体法制备了聚氨酯接枝及互穿网络改性环氧树脂,研究了酸酐为固化剂的条件下,制备工艺及聚合物结构对聚氨酯(PU)改性E-51环氧树脂(EP)性能的影响。实验确定了异氰酸酯的官能度、聚丙二醇(PPG)的分子量及聚氨酯预聚体含量等对改性产物冲击强度、微观形貌及热性能的影响。结果表明,改性材料冲击强度随PPG分子量的增高而增大;互穿网络(IPN)结构改性E-51的抗冲击性能优于接枝改性,冲击断裂面上阻碍裂纹发展的点明显多于后者;支化PU改性E-51热稳定性高于线形PU改性,280℃热失重接近未改性环氧树脂。     

聚氨酯与环氧树脂乳液互穿网络聚合物的制备

聚氨酯是一种无溶剂型的环保材料，传统聚氨酯以聚酯类与聚醚类多元醇为主[1]，而这两种软段合成的聚氨酯的耐水性能与力学性能等有待提高[2][3]。聚碳酸亚丙酯二醇拥有较好的力学性能与耐水解能力。本研究采用聚碳酸亚丙酯二醇(PCD-2000)为软段[4]合成聚氨酯(WPU)。在此基础上，使用互穿网络技术，制备聚氨酯与聚丙烯酸酯的乳液互穿网络聚合物[5](PU/EP LIPN)。本实验主要探究了聚氨酯与环氧树脂的乳液能否形成互穿网络聚合物；不同环氧树脂固化剂添加方式对PU/EP LIPN的影响；不同量的后扩链[6]和固化剂加入量对PU/EP LIPN的涂膜性能的影响。实验结果表明，聚氨酯中的环氧树脂已经固化，成功建立了互穿网络结构；使用环氧树脂聚合物对聚氨酯进行改性之后，断裂伸长率明显下降，耐水性提高；在0.5后扩链系数时，乳液胶膜拥有较好的成膜性能，力学强度；耐水性随后扩链系数的变大先增强后减弱。     

聚醚型聚氨酯/环氧树脂互穿网络聚合物的结构与性能研究

以4,4’-二苯基甲烷二异氰酸酯和聚醚及双酚A型环氧树脂为原料经共聚合成了聚氨酯(PU)/环氧树脂(EP)互穿聚合物网络(IPNs).通过改变聚氨酯结构及环氧树脂含量制备系列PU/EP的IPNs,并对其性能进行了研究.研究表明随着聚氨酯中两官能度聚醚用量增加,IPNs体系的亲水性增强、表面自由能增大;此外随着环氧树脂含量增多,整个IPNs体系的疏水性增强;力学性能测试表明,聚氨酯结构以及环氧树脂含量对PU/EP的IPNs材料力学性能影响较大.     

玻璃纤维/云母改性环氧树脂/聚氨酯互穿网络聚合物的制备与性能

以端-NCO的聚氨酯(PU)预聚体与环氧树脂(EP)WSR-618为原料,制备了聚氨酯含量20%(质量分数,下同)的PU/EP互穿聚合物网络(IPN),并用不同含量的玻璃纤维,玻璃纤维/云母混合填料对其进行改性。考察了复合材料的拉伸、冲击、动态力学性能以及热分解性能,发现玻璃纤维增强复合材料的拉伸强度最大可提高4%,填料的加入使得复合材料的储能模量增大15%以上,热分解温度最大可提高15℃。并且,复合材料的性能变化与填料的种类、含量密切相关。     

聚氨酯/环氧树脂接枝共混物的制备及性能

聚氨酯/环氧树脂亲水性能低,不适合制作涂料。以2,4-甲苯二异氰酸酯、聚乙二醇单甲醚和环氧树脂为原料,通过2步聚合法合成了亲水性能较好的聚氨酯/环氧树脂(PU/EP)接枝共混物。利用Spectrum BXⅡ红外光谱、JGW-360型接触角测定仪、TH-5000N型电子万能试验机、METTLER-TOLEOO型动态力学分析仪研究了PU/EP接枝共混物的价键结构,PU与EP的配比对其亲水性、吸水率、力学强度和损耗因子等性能的影响。结果表明:2步聚合法成功地制备了PU/EP接枝共混物;随着PU含量的提高,PU/EP接枝共混物的亲水性、吸水率和拉伸强度都有所提升,剪切强度有一定程度的下降,玻璃化转变温度逐渐降低,内耗峰呈现先变窄后变宽的趋势;PU和EP含量分别是60%和40%时为最佳配比。     

蒙脱土改性PU/EP IPN的研究

本文通过端异氰酸酯基聚氨酯预聚体与环氧树脂E-51形成了互穿网络,并通过热重分析仪(TGA)研究了完全固化后的互穿网络的热分解行为;透射电镜研究了IPN的相分离行为及用拉伸强度,断裂伸长率对其进行了力学性能的表征.结果表明,经过环氧树脂改性的聚氨酯的耐热性能比纯聚氨酯得到了提高,且力学性能也有所改善.并选取性能较好的PU/EP IPN,用纳米级有机蒙脱土对其进行了改性.研究发现,经有机纳米蒙脱土改性的PU/EP IPN的力学性能及耐热性有了进一步的提高.     

室温固化环氧树脂结构胶粘剂的研究

制备了室温快速固化综合性能较好的聚氨酯改性环氧树脂结构胶粘剂,探讨了增韧剂,固化剂等因素对胶 粘剂力学性能的影响,通过扫描电镜分析了胶粘剂断裂面的形貌特征,研究了胶粘剂形貌特征与力学性能的关系.研究结果表明:聚氨酯增韧环氧树脂既有物理交联产生"强迫互溶"和"协同效应",又与环氧树脂发生了化学反应,产生的化学键进一步加强了聚合物交联密度和聚合物的强度,当PU预聚体含量为环氧树脂40%时,聚氨酯与环氧树脂形成的互穿网络聚合物互穿程度最大,制备的胶粘剂力学性能最优,室温剪切强度达到20.16MPa.     

SiC粒子改性聚氨酯/环氧树脂复合材料性能研究

利用聚氨酯预聚体对环氧树脂(EP)进行改性制备聚氨酯/环氧树脂复合材料,再加入碳化硅(SiC)粒子作为无机填料对复合材料改性。结果表明:改性后的复合材料力学、耐磨、防腐等性能均得到了提高,当SiC粒子的加入量为复合材料的6%时,复合材料的冲击强度为24.28kJ/m2,拉伸强度为66.19MPa,均达到最大值,磨损量为0.083g,提高了耐磨性能,耐酸碱腐蚀性能达到最佳。     

负热膨胀ZrW_2O_8改性环氧树脂性能研究

采用硅烷偶联剂处理的负热膨胀材料ZrW2O8超细粉体与环氧树脂(EP)共混制备ZrW2O8/EP复合材料.检测了不同ZrW2O8含量下复合材料的冲击强度、拉伸强度、拉伸断口形貌、洛氏硬度、线膨胀系数和玻璃化温度.结果表明ZrW2O8粉体对EP有较好的改性作用:当ω(ZrW2O8)∶ω(EP)＝16∶100时复合材料的冲击韧性和拉伸强度达最大,分别为16.13kJ/m2和55.86MPa;ZrW2O8对复合材料洛氏硬度影响不大,但降低了线膨胀系数,ω(ZrW2O8)∶ω(EP)＝20∶100时线膨胀系数降至3.7322×10-5/K;复合材料的玻璃化温度在124～129℃之间.     

马来酸酐接枝乙烯辛烯共聚物和6K碳纤维混合填充对聚酰胺66性能的影响研究

以6K碳纤维作为主要增强材料,加入相容剂马来酸酐接枝乙烯辛烯共聚物(POE-g-MAH)制备聚酰胺66增强增韧复合材料,对复合材料的摩擦学性能和力学性能进行了表征。通过对比相容剂加入前后材料的摩擦系数、磨损体积以及摩擦界面温度来研究POE-g-MAH的加入对复合材料摩擦学性能的影响;另一方面,POE-g-MAH的加入改善了复合材料的力学性能(对比15%碳纤维情况下):未添加时材料的拉伸强度为47.88MPa,缺口冲击强度为7.47kJ/m2。添加后材料拉伸强度为94.80MPa,其缺口冲击强度可达到9.56kJ/m2。其拉伸强度提高了98%,缺口冲击强度提高了28%。     

凝固科学技术与材料

从凝固科学与实践发展的角度介绍了当前凝固材料体系的基本框架和凝固科学主要发展阶段的基本理论。作为材料科学与工程的基本组成，凝固科学技术正在现代科学理论的基础上针对传统材料的改性提高和新材料的发展需求，以控形、控构、控性为目标开展优质铸件的定向、晶体生长、快凝、深过冷及各种新型和超常领域凝固过程的研究，并介绍了其中某些方面和展望了可能的发展趋势。     

The Candela and Photometric and Radiometric Measurements

The national measurement system for photometric and radiometric quantities is presently based upon techniques that make these quantities traceable to a high-accuracy cryogenic radiometer. The redefinition of the candela in 1979 provided the opportunity for national measurement laboratories to base their photometric measurements on optical detector technology rather than on the emission from high-temperature blackbody optical sources. The ensuing technical developments of the past 20 years, including the significant improvements in cryogenic radiometer performance, have provided the opportunity to place the fundamental maintenance of photometric quantities upon absolute detector based technology as was allowed by the 1979 redefinition. Additionally, the development of improved photodetectors has had a significant impact on the methodology in most of the radiometric measurement areas. This paper will review the status of the NIST implementation of the technical changes mandated by the 1979 redefinition of the candela and its effect upon the maintenance and dissemination of optical radiation measurements.     

PSD和PWELCH函数的分析改进及应用

针对MATLAB中两个内建功率谱密度计算函数psd()和pwelch()计算结果迥异的现象,在功率谱密度估计理论的基础上,根据经典的周期图理论和Welch平均周期图方法,通过详细分析源程序,解析计算方法,发现psd()计算的并不是工程单边功率谱密度,而是采样信号双边谱,故与pwelch()结果迥异,另外pwelch()不能对分段信号数据进行预处理。就上述不足提出了相应的改进措施,比较验证表明改进措施行之有效。     

江澳两地高校文创设计的协同研究与商业实践

目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。     

Creation and motion of dislocations and fracture in metal and silicon crystals

By making a step on one surface ( ) of a rectangular small paralellepiped copper crystal, dislocations could be created by the molecular dynamic method. The dislocation created was not a complete edge dislocation but a pair of Heidenreich-Shockley partial dislocations. Each time a dislocation was created, the stress on the surface was released. Small copper crystals having a notch were pulled (until fracture), compressed and buckled by use of the molecular dynamic method. An embedded atom potential was used to represent the interaction between atoms. Dislocations were created near the tip of the notch. A very sharp yield stress was observed. The results of high speed deformations of pure silicon small crystals using the molecular dynamics are presented. The results suggest that plastic deformation may be possible for the silicon with a high speed deformation even at room temperature. Another small size single crystal, the same size and the same surfaces, was compressed using molecular dynamic method. The surfaces are {110}, {112} and {111}. The compressed direction was [111]. It was found that silicon crystals are possible to be compressed with a high speed deformation. This may suggest that silicon may be plastically deformed with high speed deformation.     

Error and uncertainty in modeling and simulation

This article develops a general framework for identifying error and uncertainty in computational simulations that deal with the numerical solution of a set of partial differential equations (PDEs). A comprehensive, new view of the general phases of modeling and simulation is proposed, consisting of the following phases: conceptual modeling of the physical system, mathematical modeling of the conceptual model, discretization and algorithm selection for the mathematical model, computer programming of the discrete model, numerical solution of the computer program model, and representation of the numerical solution. Our view incorporates the modeling and simulation phases that are recognized in the systems engineering and operations research communities, but it adds phases that are specific to the numerical solution of PDEs. In each of these phases, general sources of uncertainty, both aleatory and epistemic, and error are identified. Our general framework is applicable to any numerical discretization procedure for solving ODEs or PDEs. To demonstrate this framework, we describe a system-level example: the flight of an unguided, rocket-boosted, aircraft-launched missile. This example is discussed in detail at each of the six phases of modeling and simulation. Two alternative models of the flight dynamics are considered, along with aleatory uncertainty of the initial mass of the missile and epistemic uncertainty in the thrust of the rocket motor. We also investigate the interaction of modeling uncertainties and numerical integration error in the solution of the ordinary differential equations for the flight dynamics.     

Miniature and MEMS-type vacuum sensors and pumps

In the paper, the observable trends of the actual research and development of selected types of miniature and MEMS-type vacuum sensors are presented. Some information about the new types of active vacuum gauges, which are offered by the leading manufacturers of the vacuum measurement instruments, is given. Next, the list of MEMS devices that need vacuum for proper operation is presented. Some aspects of vacuum-encapsulation of MEMS devices, on wafer level and package level are shown. The new conceptions of obtaining and maintenance of high and ultra-high vacuum in MEMS devices are described. They concern the conception of integration of a miniature orbitron pump on-chip with MEMS-type device or with vacuum part of the portable advanced instruments such as electron microscope, ion mass spectrometer, and free electron laser.