二(2,3—二溴丙基)烯丙基异三聚氰酸酯对丙烯酸系树脂的阻燃研究

用氧指数(LOI)、热失重(TGA)、微分热失重(DTG)等方法研究了二(2,3—二溴丙基)烯丙基异三聚氰酸酯对丙烯酸系树脂阻燃性的影响。结果表明二(2,3—二溴丙基)烯丙基异三聚氰酸酯对丙烯酸系树脂有一定的阻燃作用,与三氧化二锑配用时具有阻燃协同效应,阻燃效果较好,与磷酸三甲苯酯配用时没有协同效果。     

案例教学法在《计算机基础》教学中的应用研究

随着时代的发展,科技信息的进步对人才的所具备的信息处理的能力提出了很高的要求,计算机基础课程在各类院校都是一门非常重要的公共基础课程,为了更好的让学生掌握好这门课程,计算机教学方法是非常有必要创新的,本文主要介绍案例教学法在计算机基础教学中的优势及其存在的问题等进行研究.     

裂解汽油加氢装置二段反应器缺陷分析

对中国石油吉林石化公司300 kt/a乙烯装置汽油加氢二段反应器接管与筒体焊接接头的缺陷进行详细分析。阐明了缺陷的产生是由于在焊接过程中焊缝熔合区内形成马氏体、增碳层并伴有δ-铁素体的分解而使熔合区内及焊缝处的材质脆化。由于选用焊接材料的错误,产生较高的焊接残余应力致使焊缝开裂。分析了焊缝马氏体、增碳层及δ-铁素体分解的原因。     

纳米SiOx改性不饱和聚酯树脂

用纳米SiOx粒子对298#不饱和聚脂(UPR)进行增强、增韧改性，发现随粒子用量增加，树脂凝胶时间、粘度增大；粒子用量为0．5％时树脂有脆韧转变现象；用量为3％时，拉伸强度和断裂延伸率分别提高约33％和60％。用KH-570偶联剂进行表面处理有助于提高纳米SiOx粒子在UPR中的均匀分散。     

Surface and interfacial FTIR spectroscopic studies of latexes. IX. The effect of homopolymer and copolymer structures on surfactant mobility in Sty/BA latices

The effects of homopolymer and copolymer compositions and structures in styrene/n-butyl acrylate (Sty/BA) latices on sodium dioctyl sulfosuccinate (SDOSS) surfactant mobility and its preferential concentration at the film–air (F–A) and film–substrate (F–S) interfaces were examined using attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy. It appears that the SDOSS concentration at the F–S interface is highest when the Sty/BA feed ratio is 50/50, and the excess of Sty results in migration of SDOSS surfactant to the F–A interface. This behavior is attributed to the increased glass transition temperature and diminished compatibility between surfactant molecules and copolymer latex. This study also shows that the primary factors that influence exudation to either F–A or F–S interfaces are surface tension of the substrate, glass transition temperature, water flux during coalescence, and compatibility between latex components. © 1995 John Wiley & Sons, Inc.     

Formation of novel polymeric nanoparticles

We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.     

Acceleration or retardation to crystallization if liquid-liquid phase separation occurs: Studies on a polyolefin blend by SAXS/WAXD, DSC and TEM

Blends of statistical copolymers containing ethylene/hexene (PEH) and ethylene/butene (PEB) exhibited the behavior of upper critical solution temperature (UCST). The interplay between the early and intermediate stage liquid-liquid phase separation (LLPS) and crystallization of the PEH/PEB 50/50 blend was studied by time-resolved simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. Samples were treated by two different quench procedures: in single quench, the sample was directly quenched from 160 °C to isothermal crystallization temperature of 114 °C; while in double quench, the sample was firstly quenched to 130 °C for 20 min annealing, where LLPS occurred, and then to 114 °C. It was found that in the early stage of crystallization, the integrated values of Iq² and crystallinity, X_c, in the double quench procedure were consistently higher than those in the single quench procedure, which could be attributed to accelerated nucleation induced by enhanced concentration fluctuations and interfacial tension. In the late stage of crystallization, some morphological parameters were found to crossover and then reverse, which could be explained by retardation of lamellar growth due to phase separation formed during the double quench procedure. This phenomenon was also confirmed by DSC measurements in blends of different compositions at varying isothermal crystallization temperatures. The crystal lamellar thickness determined by SAXS showed a good agreement with TEM observation. Results indicated that the early stage LLPS in the PEH/PEB blend prior to crystallization indeed dictated the resulting lamellar structures, including the average size of lamellar stack and the stack distribution. There seemed to be little variation of lamellar thickness and long period between the two quenching procedures (i.e., single quench versus double quench).     

Synthesis and characterization of soluble aromatic azopolyamides containing sulfone and ether units

A series of new polyamides 3a–d containing aryl-azo, ether and sulfone groups in the main chain were synthesized from bis[4-(4-aminophenoxy)phenyl sulfone] 1 and several azo aromatic diacyl chlorides 2a–d by the low temperature solution polycondensation technique. FTIR spectroscopy, nuclear magnetic resonance (NMR) and elemental analyses confirmed the structure of these polymers. Owing to the aryl and amide groups in the main chain, these polymers exhibit photochromic properties as well as excellent thermal stabilities. The transition temperatures (T _g) are between 242 and 265 °C, and the char yields at 800 °C in nitrogen atmosphere were above 39%. Based on incorporation of flexible ether linkages and polar sulfone groups, the polyamides show desirable solubility in organic solvents such as DMAc, N,N-dimethylformamide (DMF), N-methyl-2-pyrroidinone (NMP) and dimethylsulfoxide (DMSO). And it is exemplified that polyamide containing 2 and 2′ substitutes performed better solubility. Funded by the National Natural Science Foundation of China (No. 50572081)     

高职创业教育的多元困境与发展策略

创业教育是一项系统工程。它的教育过程是通过各种可利用的教育方式来培养创业者的创业意识、创业思维、创业技能等各种创业综合素质,并最终使被教育者具有一定的创业能力。这既是大学生就业的需要,更是高职院校主动适应社会经济发展服从于创新型国家战略发展的根本要求,同时也有助于使高职教育由片面的强调功利化的职业培训,转向关注学生的现实而具体的生存,让学生通过高职创业教育,提升和转化为真正完满而自由的职业人。