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101.
The melt rheological analysis of high‐density polyethylene reinforced with vapor‐grown carbon nanofibers (VGCNFs) was performed on an oscillatory rheometer. The influence of frequency, temperature, and nanofiber concentration (up to 30 wt %) on the rheological properties of composites was investigated. Specifically, the viscosity increase is accompanied by an increase in the elastic melt properties, represented by the storage modulus G′, which is much higher than the increase in the loss modulus G″. The composites and pure PE exhibit a typical shear thinning behavior as complex viscosity decreases rapidly with the increase of shearing frequency. The shear thinning behavior is much more pronounced for the composites with high fiber concentration. The rheological threshold value for this system was found to be around 10 wt % of VGCNF. The damping factor was reduced significantly by the inclusion of nanofibers into the matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 155–162, 2004 相似文献
102.
Because of their large specific surface area, aqueous‐based pseudolatex systems of ethylcellulose can absorb large amounts of drugs. In addition, the stability of polymeric particles in biological fluids delays the release of the drug as in controlled drug delivery systems. The aim of the present study was to characterize the rheological properties of latex particles as a measure of their colloidal stability. Here, we report the effect of three variables: pH, electrolyte concentration, and temperature. The rheograms clearly show that the polymer suspensions displayed Bingham plastic behavior. Internal structuring of the latex was greatest at acid and natural pH values, particularly at the highest ionic strength. In acid solutions, only temperature appeared to play a fundamental role; both the shear stress corresponding to the onset of nonlinear viscoelasticity and the elastic modulus at all frequencies were higher at 37°C than those at room temperature. This is assumed to be a consequence of deformation of the polymer particles upon heating. The effect of ionic strength was noticeable only at the natural pH (pH ? 6.5). At high concentrations of sodium chloride, the particles aggregated because of the decrease in double layer repulsion, and as a result, the latex became structured and its elastic modulus subsequently increased. Interestingly, when the temperature was increased further, this structure presumably broke, down, at least partially, and the storage modulus was reduced. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 847–851, 2006 相似文献
103.
Shear creep resistance of styrene–isoprene–styrene (SIS)‐based hot‐melt pressure‐sensitive adhesives
The effects of the properties of substrates and tackifier on the shear creep of SIS‐based HMPSAs were investigated. The holding power (tb) and shear adhesion failure temperature (SAFT) were measured. The relationship between the complex viscosity and the holding power was examined. The holding power and SAFT values of the triblock SIS blends were higher than those of the diblock‐containing SIS blends, perhaps because blends using triblock SIS have higher crossover temperature and complex viscosity than those using diblock‐containing SIS. Higher levels of aromatic resin‐modified aliphatic tackifier and rosin ester were found to decrease the holding power of the HMPSAs. This maybe due to the fact that rosin ester and aromatic‐modified aliphatic resin are compatible with both the ends and midblocks of SIS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 825–831, 2006 相似文献
104.
蔗渣浆低浓黑液多聚物粘度对温度依赖性的关联模型 总被引:3,自引:1,他引:3
利用聚合物自由体积理论模拟了蔗渣浆低浓黑液对粘度对温度的依赖性的数学模型,最终得出黑液多聚物粘度与温度的相关式:η=A1exp[B1/(T-T0)]。利用示差扫描量热分析技术(DSC)得出了蔗渣黑液多聚物中连续相与分散相的转变曲线,并获得了表观温度T0的平均值为255K;通过实验数据拟合可回归出蔗渣黑液多聚物在不同浓度时的系数A1和B1值。因此,使用该粘度的数学模型可估算蔗渣低浓(接近40%固含量)黑液多聚物在操作温度范围内(20-100℃)的粘度值。 相似文献
105.
界面剪切黏度对原油乳状液稳定性的影响 总被引:4,自引:2,他引:4
对孤东一号联合站及孤东四号联合站(简称孤东1#及孤东4#)两种原油及其分离组分(饱和分、芳香分、胶质、沥青质)配成模拟油,测定了模拟油与碱水〔w(Na2CO3)=1 2%〕体系的界面剪切黏度。原油浓度越大,界面剪切黏度越大;沥青质模拟油/碱水界面剪切黏度最大,在油/碱水间形成了一定强度的界面膜,膜的强度大于饱和分、芳香分、胶质的界面膜强度;孤东4#沥青质模拟油/碱水的界面剪切黏度大于孤东1#沥青质的界面剪切黏度。在剪切速率为0 3rad·s-1时,原油及胶质的油/碱水界面剪切黏度不随时间变化。 相似文献
106.
A new, simple and reliable empirical correlation for predicting the viscosities of heavy petroleum fractions is proposed, applicable to fractions with mid-boiling points from 80 to 550°C over a wide range of viscosities (0.4 to 260 mm2 s−1) and measurement temperatures (40 to 200°C). This correlation showed better accuracy in the prediction of heavy petroleum fraction viscosities than that of the most accurate and much more complicated predictive methods in the literature, since it gave an overall average absolute deviation of 6.5% when tested on 296 data for medium and heavy petroleum fractions. 相似文献
107.
Viscosity measurements under Newtonian flow conditions had been performed on cetyltrimethylammonium bromide (CTAB) aqueous
solutions in the combined presence of sodium salts of aromatic acids (sodium salicylate, NaSal; sodium benzoate, NaBen; sodium
anthranilate, NaAn) and organic additives (1-hexanol, C6OH; n-hexylamine, C6NH2) at 30°C. On addition of C6OH or C6NH2, the viscosity of 25 mM CTAB solution remained nearly constant without salt as well as with a lower salt concentration. This
is due to low CTAB concentration which is not sufficient to produce structural changes in this concentration range of salts.
However, as the salt concentration was increased further, the effect of C6OH/C6NH2 addition was different with different salts: The viscosity first increased; then a decrease was observed with the former
while with C6NH2 a decrease followed by constancy appeared in plots of relative viscosities (η
r
) vs. organic additive concentrations. At further higher salt concentration, the magnitude of η
r
was much higher. The viscosity increase is explained in terms of micellar growth and the decrease in terms of swollen micelle
formation (due to interior solubilization of organic additive) or micellar disintegration (due to formation of water + additive
pseudophase). 相似文献
108.
用粘度法和核孔膜过滤法研究了实验室自制相对分子质量约1000万的疏水缔合聚丙烯酰胺(HAP)溶液的缔合效应,用粘度计考察了电解质浓度、温度和剪切速率对HAP溶液表观粘度的影响,并与相同测试条件下相对分子质量为1770万的部分水解聚丙烯酰胺3530进行对比。结果表明:HAP溶液在70℃的高温和矿化度为5727的高盐条件下,在1000mg/kg附近存在一临界缔合浓度,在临界缔合浓度以上,HAP溶液粘度迅速增加;而3530不存在临界缔合浓度,粘度增加缓慢。浓度为1250mg/kg的HAP溶液通过核孔膜20mL的过滤时间是347.3min,而相同浓度下3530的过滤时间仅为2.1min。浓度为1000mg/kg的HAP溶液即使在矿化度为30000、70℃的高温、30r/min转速的条件下,粘度仍达到32.8mPa·s,而聚合物3530的粘度仅有4.11mPa·s;当剪切速率增加到140r/min、温度为70℃,用矿化度为5727的模拟采出水配制的HAP溶液的粘度为9.21mPa·s,而3530溶液的粘度仅5.18mPa·s。HAP具有良好的耐温抗盐抗剪切能力。 相似文献
109.
以玉米黄粉酶解液为氮源应用于黄原胶发酵培养基,探讨了蛋白酶种类、玉米黄粉酶解液添加量和酶添加量等因素对其发酵黄原胶粘度和产胶率的影响,并优化了复配氮源的种类及其复配比例。结果表明,碱性蛋白酶水解液作为氮源发酵黄原胶的粘度和产胶率优于其它蛋白酶解液;当酶解液添加量为6%、碱性蛋白酶添加量为8kU时,发酵黄原胶的粘度和产胶率可以达到4235cp和24.4g/L。大豆蛋白与玉米黄粉酶解液复配效果优于与棉籽粉、豆粕粉、花生粉的复配;玉米黄粉酶解液与大豆蛋白复配比为3:7时,发酵黄原胶的粘度和产胶率可以达到5833cp和32.4g/L,与单独以大豆蛋白为氮源无明显差异。本研究为提高玉米黄粉资源利用率、降低黄原胶的发酵生产成本提供了新思路。 相似文献
110.