加成型硅橡胶灌封料流变性能的研究

研究了加成型硅橡胶灌胶封料的注性能。测定了硅橡胶灌封料的粘度，讨论了配制工艺条件及组份对硅橡胶灌封料流变性能的影响，分析了白炭黑在硅橡胶灌封料中的分散状态，实验结果表明，通过改进配制工艺条件，优化组分，可以制备出满足特定需要并具有高流动性的硅橡胶灌封料。     

热处理对照相明胶溶液粘度和分子量分布的影响

本文以四种照相明胶为研究对象，探讨热处理对照相胶胶溶液粘度和分子量分布的影响，实验结果表明，随着加热温度上升，照相明胶溶液粘度下降，数均分子量下降，照相明胶溶液粘度和数均分子量密切相关，照相明胶溶液粘度下降发生的内在原因是数均分子量下降，在本实验条件下，惰胶、活性胶的加热温度不超过７５℃，ＰＡ胶的加热温度不超过６０℃。     

Viscosity aging of poly(vinyl chloride) plastisol: The effect of the resin type and plasticizer type

The viscosity of freshly prepared poly(vinyl chloride) (PVC) plastisol increases with time, and this phenomenon is called viscosity aging. The increase is rapid in the beginning and slows down to a quasistable value, but a very slow increase continues. The phenomenon may be a result of either the deagglomeration of agglomerated particles or the dissolution of low‐molecular‐weight PVC into the plasticizer. In this work, two typical commercial resins were used, one containing friable agglomerates and the other containing nonfriable agglomerates. With the friable‐agglomerate resin, about 40% of the initially present agglomerates deagglomerated, whereas the viscosity increased in a week to twice the initial value. With the nonfriable‐agglomerate resin, very fine and very low molecular weight particles, about 3% of all the particles, dissolved into the plasticizer in 2 days. The effect of the plasticizer type on the viscosity aging through deagglomeration was investigated with four plasticizers and three plasticizer blends. The emulsifiers used for polymerization, and retained through drying, affected the aging in the beginning. On the other hand, the viscosity after 1 week was free from the effect of the emulsifier and was affected only by the plasticizer type. With the exception of two blends, the 1‐week viscosity was quantitatively related to the dielectric constant divided by the molecular weight of the plasticizer. For the plasticizer blends, one of the plasticizers could have a dominant effect on the promotion of deagglomeration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 448–464, 2005     

Effect of time/temperature treatment parameters on depolymerization of chitosan

Depolymerization of the biopolymer chitosan by an autoclaving process at 121°C and 15 psi was investigated using various treatments. Acetic acid was found to be the most effective solvent in decreasing chitosan viscosity among the six organic acids tested. The rate of viscosity decrease increased with increasing chitosan concentration. The viscosity of 1% chitosan in 1% acetic acid decreased rapidly to 91% of the initial viscosity following the initial 15 min of autoclaving. This decreased gradually to 93% and 94% in 30 and 60 min, respectively, without being adversely affected by the chitosan solution volume. The degree of deacetylation was comparable before and after autoclaving for 60 min. Chitosan at three molecular weights (M_r = 1597, 1110, and 789 kDa) decreased in molecular weight by 46%–51% in the 15‐min treatment, 55%–60% in the 30‐min treatment, and 60%–62% in the 60‐min treatment. The addition of 0.1%–1.0% (v/v) concentrations of hydrogen peroxide to the chitosan solution autoclaved for 15 min decreased viscosity by 94%–98% and molecular weight by 69%–83%. This process is a simple, timesaving, homogeneous depolymerization procedure, and it is possible to prepare partially hydrolyzed chitosan with specified molecular weights by regulating the time of treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1890–1894, 2003     

球形磷酸铁锂材料的制备及其18650电池的测试

采用高能球磨和喷雾干燥法制备了球形磷酸铁锂材料LFP-1,并制作18650实装电池,测试电极片的压实密度,同时选择一种商业化磷酸铁锂材料LFP-2作为对比。测试结果显示,2种LFP材料均由平均粒径为300~500 nm的一次颗粒组成,比表面积为13~15 m²/g,碳质量分数为1.5%左右。通过CR2032纽扣型电池充放电测试表明,在0.2C时,LFP-1的比放电容量约为165 mA·h/g,与商业化磷酸铁锂材料LFP-2相近。制备18650电池的结果表明,商业化磷酸铁锂LFP-2材料制备的电极片的最高压实密度可以达到2.52 g/cm³,显著高于实验室制得的磷酸铁锂材料LFP-1的最高压实密度2.25 g/cm³,这可能与材料的颗粒粒度分布不同有关。     

一缩二乙二醇二缩水甘油醚的合成

以一缩二乙二醇和环氧氯丙烷为原料、三氟化硼乙醚络合物为催化剂合成一缩二乙二醇二缩水甘油醚(DGEG)。讨论了催化剂用量、原料配比、碱金属氢氧化物以及成环反应温度对产物收率的影响。同时 ,用傅立叶红外光谱对其进行了分析与表征。当三氟化硼乙醚络合物用量为 3份、环氧氯丙烷与一缩二乙二醇的物质的量比为 8∶1、用氢氧化钾在 30℃左右进行成环反应时 ,可以得到低粘度、高收率的产物。     

Effects of the o‐aromatic ring in the molecular chain on the properties of polyester polyols

A series of liquid polyester polyols from adipic acid (AA), phthalic anhydride (PA), ethylene glycol, propanediol‐1,2, and trihydroxymethylpropane, varying in the molar ratio of PA to AA, were prepared. The effects of the o‐aromatic ring in the molecular chain, which came from PA, on the viscosity, glass‐transition temperature, and thermal degradation temperature of the polyester polyols were studied with viscometry, differential scanning calorimetry, and thermogravimetry. The intrinsic viscosity and glass‐transition temperature increased with the concentration of the o‐aromatic ring increasing. The temperature of the maximum thermal degradation rate for aliphatic polyester polyols was 434.20°C. Two steps of thermal degradation were found when there were o‐aromatic rings in the molecular chain. One thermal degradation temperature was 358.36–360.48°C, and the other was 412.85–427.18°C. Polyester polyols with o‐aromatic rings had higher stability at lower temperatures (<240.00°C). However, aliphatic polyester polyols had higher stability at higher temperatures (300.00–480.00°C). The activation energy and order of degradation were calculated from thermogravimetric curves. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1617–1624, 2002     

A numerical study of particle wall-deposition in a turbulent square duct flow

The deposition of dense solid particles in a downward, fully developed turbulent square duct flow at Re_τ = 360, based on the mean friction velocity and the duct width, is studied using large eddy simulations of the fluid flow. The fluid and the particulate phases are treated using Eulerian and Lagrangian approaches, respectively. A finite-volume based, second-order accurate fractional step scheme is used to integrate the incompressible form of the unsteady, three-dimensional, filtered Navier-Stokes equations on an 80 × 80 × 128 grid. A dynamic subgrid kinetic energy model is used to account for the unresolved scales. The Lagrangian particle equation of motion includes the drag, lift, and gravity forces and is integrated using the fourth-order accurate Runge-Kutta scheme. Two values of particle to fluid density ratio (ρ_p/ρ_f = 1000 and 8900) and five values of dimensionless particle diameter (d_p/δ × 10⁶ = 100, 250, 500, 1000 and 2000, δ is the duct width) are studied. Two particle number densities, consisting of 10⁵ and 1.5 × 10⁶ particles initially in the domain, are examined.Variations in the probability distribution function (PDF) of the particle deposition location with dimensionless particle response time, i.e. Stokes number, are presented. The deposition is seen to occur with greater probability near the center of the duct walls, than at the corners. The average streamwise and wall-normal deposition velocities of the particles increase with Stokes number, with their maxima occurring near the center of the duct wall. The computed deposition rates are compared to previously reported results for a circular pipe flow. It is observed that the deposition rates in a square duct are greater than those in a pipe flow, especially for the low Stokes number particles. Also, wall-deposition of the low Stokes number particles increases significantly by including the subgrid velocity fluctuations in computing the fluid forces on the particles. Two-way coupling and, to a greater extent, four-way coupling are seen to increase the deposition rates.     

粘度调节剂对制备环氧树脂微球的影响

研究粘度调节剂对环氧树脂/二氨基二苯基砜/聚醚酰亚胺(EP/DDS/PEI)共混物相结构及制备EP微球的影响。结果表明,共混物中加入粘度调节剂后,固化过程中共混体系的粘度明显降低,随着粘度调节剂用量的增加,EP分散相尺寸逐渐增大,制得的EP微球粒径及粒径分布指数逐渐增大。EP微球的红外光谱显示粘度调节剂对EP微球的成分和相结构没有明显影响。     

试验温度和停放时间对胶料加工性能的影响

研究试验温度和停放时间对胶料加工性能的影响。结果表明，试验温度对胶料的门尼粘度、门尼焦烧时间和硫化特性均有一定影响。门尼粘度测定的试验温度选择100℃；门尼焦烧时间测定的试验温度一般选120℃，SBR胶料可提高至130℃左右，以缩短试验时间；硫化特性测定的试验温度一般选185℃。试验前模腔达到规定温度后再保持15min，以使转子与模腔温度一致。胶料停放时间应控制在2h左右。