共查询到20条相似文献,搜索用时 921 毫秒
1.
采用磷酸/多聚磷酸为溶剂溶解纤维素,制备了具有液晶性能的纺丝原液,相对于粘胶法大大缩短了纤维素溶解时间;并采用液晶纺丝工艺,制得了强度为2.04cN/dtex、模量为90.72cN/dtex的纤维素纤维。 相似文献
2.
3.
4.
5.
《塑料》2017,(4)
使用超声波、18%NaOH溶液及饱和CaCl_2水溶液对纤维素进行预处理,预处理前后纤维素的结构利用偏光显微镜、扫描电子显微镜、红外光谱及X-射线衍射进行表征。将不同条件预处理后的纤维素溶解在磷酸与磷酸脲的复合溶剂中,可以发现,超声波对加快纤维素溶解的效果最为明显。又分别将预处理后的纤维素溶于磷酸(H_3PO_4)-磷酸脲(H_3O_4P·CH_4N_2O)、磷酸-六偏磷酸钠(Na_6P_6O_(18))、磷酸-磷酸二氢钾(KH_2PO_4)、磷酸-磷酸氢二钾(K_2HPO_4)中,通过对比发现,纤维素在35℃下磷酸-磷酸脲中的溶解效果最好,并且聚合度降解最小。 相似文献
6.
7.
纤维素衍生物,如乙基纤维素,甲基纤维素,乙基氰乙基纤维素,乙基醋酸纤维素等与二氯乙酸所形成的溶液在浓度达到临界值以上后,出现胆甾型液晶相。在这类溶液中,液晶相的织态结构具有多重性,即胆甾型液晶相的织构随溶液浓度和温度而变化。在不同的浓度范围内,溶致性液晶可呈现出圆盘织构,条纹织构,假各向同性织构和具有鲜艳色彩的平面织构。这些织构均具有胆甾型液晶的特征。在液晶相刚形成,溶液处于 相似文献
8.
链长法是利用多聚磷酸在未水解时以氢氧化钠溶液为滴定溶液,用自动电位滴定仪滴定,并记录滴定曲线,根据曲线上的两个拐点处所消耗的氢氧化钠的体积,计算多聚磷酸中磷酸的含量。该法样品处理和分析过程简单、快速、准确、成本低,能满足多聚磷酸生产和产品检验的要求。 相似文献
9.
10.
微波条件下磷酸快速水解纤维素得到葡萄糖,而葡萄糖可替代甲醛制备新型环保PF(酚醛树脂)。以微波功率、反应时间和反应温度为试验因素,以葡萄糖产率为考核指标,采用正交试验法优选出磷酸水解纤维素的最佳工艺条件。结果表明:各因素对磷酸水解纤维素的影响依次为反应温度>反应时间>微波功率;当微波功率为240 W、反应温度为100℃和反应时间为40 s时,水解液中葡萄糖含量为80.7%,葡萄糖浓度为40.35 g/L;超声波能加快纤维素在磷酸中的溶解速率,常温时纤维素完全溶解在磷酸中需要72 h,而微波条件下纤维素完全溶解在磷酸中只需2 h。 相似文献
11.
A thin-film evaporation from a surface of a axisymmetrical body in a humid air stream was studied using a finite difference method associated with Thomas' algorithm. The surface of the body is supposed isothermal. The variability of physical properties is taken into account, and a steady-state and laminar regime is supposed. The influence of the main parameters of the system on the evaporation is determined, especially the wall profile. It is shown that, for certain conditions of calculation, it is possible to find a flat ellipsoid of revolution offering a uniformly accessible wall between the pole and the equator. 相似文献
12.
为了降低递推部分最小二乘(RPLS)建模方法的模型校正频率,开发了一种基于模型性能评估的RPLS(MPA-RPLS)模型.首先,根据过程的初始特性,自动生成模型的置信限,以均方根误差(RMSEP)为性能指标,评估模型性能;依据模型性能的评估结果,选择性地启动模型校正和置信限校正.然后,引入滑动平均滤波器消除过程变量中的噪声,探讨噪声对模型性能的影响程度.最后,将MPA-RPLS模型应用于一个化学反应过程--C8芳烃临氢异构化过程,基于大量工业数据,进行仿真验证.仿真结果表明:本文开发的模型仅以微小的精度损失换取了模型计算效率的大幅提高(即模型校正频率大幅下降);滑动平均滤波器可有效地处理变量的噪声,改善模型的预测精度. 相似文献
13.
Anthony D. Rosato Denis L. BlackmoreNinghua Zhang Yidan Lan 《Chemical engineering science》2002,57(2):265-275
Segregation of particulate mixtures is a problem of great consequence in industries involved with the handling and processing of granular materials in which homogeneity is generally required. While there are several factors that may be responsible for segregation in bulk solids, it is well accepted that nonuniformity in particle size is a fundamental contributor. When the granular material is exposed to vibrations, the question of whether or not convection is an essential ingredient for size segregation is addressed by distinguishing between the situation where vibrations are not sufficiently energetic to promote a mean flow of the bulk solid, and those cases where a convective flow does occur. Based on experimental and simulation results in the literature, as well as dynamical systems analysis of a recent model of a binary granular mixture, it is proposed that “void-filling” beneath large particles is a universal mechanism promoting segregation, while convection essentially provides a means of mixing enhancement. 相似文献
14.
In a rectangular fluidized bed combustor,the tracer gas is injected continuously into the bed from a point source at the center of the distributor plate.In this study,a general governing equation is formulated for tracer gas dispersion in the bed.An analytical solution is derived to estimate the dispersion coefficients,Dx and Dy,in a horizontal plane.The concentration profiles at different sampling heights with various gas velocities are plotted.Subsequently,to estimate the dispersion coefficients,surface fitting of the obtained analytical solution to the experimental data is performed.The dispersion coefficients obtained from this model are compared with those of a conventional model.Additionally,the effect of walls,bed height and gas injection rate on the dispersion coefficients in a horizontal plane is investigated,and the effect of distributor design on the dispersion coefficients in a horizontal plane is investigated with different tracer positions.It is found that Dx and Dy are nearly equivalent at a lower tracer gas ratio of the injected gas to the total gas flow rate.It is also demonstrated that the effect of bed height on Dx is minor.This model is also able to estimate the dispersion coefficients in the case of a multihorizontal nozzle distributor. 相似文献
15.
用高相对分子质量酚类主抗氧剂和具有碳自由基捕捉剂的辅助抗氧剂、表面活性剂、消泡剂、增稠剂与水通过研磨并加以复配的方法。研制出一种用于乳液聚合工艺生产ABS树脂的乳液型抗氧剂。由于该抗氧剂无需添加乳化剂即能均匀分散在丙烯腈/丁二烯/苯乙烯三元共聚物(ABS)胶乳中。在简化液体抗氧剂加入步骤的同时,改善了抗氧剂与胶乳的混合效果,使抗氧剂在ABS胶乳中的氧化诱导期延长约10%。乳液型ABS抗氧剂配方为:w(主抗氧剂A)22%;w(辅助抗氧剂B)11%;w(分散剂C)=3%:w(增稠剂D)1%;w(水)63%;w(消泡剂)为以上混合物料的0.05%。 相似文献
16.
The behavior of a floc in a flow field is analyzed theoretically; in particular, the force it experienced is estimated. Here, a floc is simulated by an entity having a two-layer type of structure, and its porous nature mimicked by varying the relative magnitudes of the permeability of its inner layer and that of its outer layer. The results of numerical simulation reveal that, for the same volume-averaged permeability, the drag coefficient of a floc with a heterogeneous structure is always much larger than that of a floc with a homogeneous structure. This is true regardless of the relative magnitudes of the permeability of the inner layer and that of the outer layer. The drag coefficient of a floc is mainly determined by the part having a less porous structure. We show that for the same volume-averaged permeability, the more heterogeneous the structure of a floc is, the easier for the relation between the drag coefficient and the Reynolds number to deviate from a Stokes’ law-like correlation. 相似文献
17.
Work exchange is a promising innovative technology in recovering residual pressure energy. However, at the systematic level, the comprehensive utilization of different energy resources in an energy system has become an issue of concern. In this work, a systematic approach is proposed, one that successively integrates heat, work and adjusts operation parameters. A detailed procedure for building a heat-work coupling transfer network is provided. The synthesis mainly consists of constructing a work exchange sub-network with pinch analysis based on positive displacement type work exchangers. Simultaneously, another kind of sub-network based on turbine-type work exchangers is built as a schematic comparison. The influence of applying a positive displacement work exchanger on the system is investigated. Finally, as a case study, a renovation design of a typical rectisol process in the coal-water slurry gasification section of an ammonia plant is presented. The results show that the added work exchanger has little impact on the existing heat exchange sub-network. Moreover, extra pressure energy is recovered by coupling the transfer network. It is concluded that the heat-work systematic design is a promising and powerful method to use energy more efficiently. 相似文献
18.
19.
George R. Romovacek 《Fuel》1982,61(5):430-432
A test, replacing the distillation test for pitches, has been developed. In this test, a sample is placed into an aluminium dish which is introduced into the cavity of a metal block preheated to a selected temperature. The surface of the sample is in a constant stream of nitrogen preheated to the temperature of the test. After an exposure of 30 min, the sample is taken out of the block and the weight loss, which is a measure of the volatility, is determined. 相似文献
20.
S. Ben Jabrallah A.S. Cherif B. Dhifaoui A. Belghith J.P. Corriou 《Desalination》2005,180(1-3):197-206
This article concerns the experimental study of heat and mass transfer in a distillation cell. This latter is a parallelepiped, of large form factor, whose active walls are vertical. The cell is fed with salt water, and pure water is evaporated from a thin film that falls along a heated wall while the opposite wall is maintained at a lower temperature and is used as a condensation surface. The experimental results show that the heat transfer in the distillation cell is dominated by the latent heat transfer associated with evaporation. A parametric study of the behavior of the distillation cell has been performed. A convenient choice of the operating parameters is suggested to optimize the distillation yield. 相似文献