MECHANISMS OF DRYING OF SKIN-FORMING MATERIALS.III. DROPLETS OF NATURAL PRODUCTS.

ABSTRACT

Drying studies were carried out on single droplets suspended from a rotating nozzle in a horizontal wind tunnel. Droplets were of solution of a third type of skin-forming material, namely the natural products skim milk or fructose. Droplet weight and temperature were measured during the drying process. Dried crusts were recovered and examined by Scanning Electron Microscopy.

With this type of material a skin first forms at any drying condition on the surface of the droplet at a cerlain stage of drying. A crust subsequently forms beneath the skin. The final dried panicle retains the structure and properties of the original powder, unless the material is dried at very high temperatures. e.g. >300 °C. which result in burning.

An increase in air temperature resulted in the formation of a smoother skin offering a higher resistance to vapour diffusion. At temperatures over 100 °C droplets exhibited puffing or ballooning phenomena; i.e. they inflated and deflated many times before forming the final dried particles.     

大豆油对丁腈橡胶增塑作用的研究

以环保大豆油用作丁腈橡胶(NBR)增塑剂,研究其用量对NBR胶料门尼粘度、流变性能和物理性能的影响,并与增塑剂261进行对比。结果表明:与增塑剂261增塑NBR胶料相比,大豆油增塑NBR胶料的门尼粘度和表观粘度较小,增塑效果和加工性能较好;当增塑剂用量为5份时,大豆油增塑NBR硫化胶的拉伸强度和拉断伸长率较大;但随着增塑剂用量的增大,大豆油增塑NBR硫化胶的物理性能变差。     

邻菲罗啉与溴离子对磷酸溶液中冷轧钢的缓蚀研究

研究了在2．0-9．0mol／L磷酸溶液体系中,邻菲罗啉单体及邻菲罗啉与溴离子复配对冷轧钢的缓蚀行为。结果表明邻菲罗啉单体对冷轧钢在磷酸溶液中缓蚀性能有限,但当与0．03mol／L溴离子复配时,表现出强烈的协同缓蚀效应,且该复配缓蚀剂尤其适用于高浓度磷酸体系,单体及复配缓蚀剂在冷轧钢表面的吸附均符合Langmuir吸附模型,吸附热、吸附熵、吉布斯自由能和吸附平衡常数等热力学参数以及表观活化能、指前因子等动力学参数也一并求得。     

复合铝锌铁有机改性混凝剂对模拟水的处理效果

采用混凝实验,对比研究了复合铝锌铁（PAZF）混凝剂及其有机改性剂[PPAZF-n,n为聚丙烯酰胺（PAM）加入量]对高浊度模拟水样的处理效果。实验结果表明,PPAZF-n的除浊效果优于PAZF,且PPAZF-5的除浊效率最高。当投药量为3mL时,PPAZF-2、PPAZF-5及PPAZF-10的余浊分别为1．93、1．16及1．99 NTU,而PAZF的余浊为2．41NTU。     

Thermogravimetric Analysis of a Cellulosic Fabric Incorporated by Synthetic Ammonium Magnesium Phosphate as a Flame-Retardant

We have investigated the effect of synthetic struvite (MgNH₄PO₄·6H₂o) on the flammability of a cellulosic fabric. It was synthesized by means of the multiple-bath method and deposited onto a cotton fabric. Its uniformity was ensured by means of squeeze rolls, obtaining the optimum effective add-on value of ammonium magnesium phosphate to impart flame retardancy to cotton fabric in the range of around 12 g anhydrous salt per 100 g fabric. A thermogravimetric analysis of pure cotton, treated cotton, and the salt was accomplished, and their thermograms were compared and commented upon. The results obtained fortified the chemical theory expressing the promotion of the formation of solid char rather than the formation of volatile pyrolysis products, during the fulfillment of thermal decomposition of the cellulosic substrate.     

Synergistic Effects of Nanoporous Nickel Phosphates VSB-1 on an Intumescent Flame-Retardant Low-Density Polyethylene (LDPE) System

Nanoporous nickel phosphates VSB-1 was synthesized by hydrothermal method, and its structure was characterized by X-ray diffraction (XRD), thermogravimetric analyses (TGA) and high resolution transmission electron microscopy (HRTEM). The flame retardancy and thermal behaviour of intumescent flame retardants (IFR) with and without VSB-1 for low-density polyethylene (LDPE) were evaluated by LOI, UL-94 burning test, TGA and cone calorimeter test. With the addition of 2 wt% VSB-1 to LDPE/IFR systems, the LOI value increases from 28.7 to 31, and UL-94 rating raises from V-1 rating to V-0 rating. The results of cone calorimeter show that heat release rate (HRR) peak decrease substantially from 511 KW/m² to 407 KW/m² with 2 wt% VSB-1 in LDPE/IFR systems. The scanning electron microscopy (SEM) indicates the quality of char forming of LDPE/IFR/ VSB-1 is superior to that of LDPE/IFR.     

The Identification of Cyclopenta-Fused and Ethynyl-Substituted Polycyclic Aromatic Hydrocarbons in Benzene Droplet Combustion Products

In order to investigate new aspects of polycyclic aromatic hydrocarbon (PAH) growth and soot formation, we have synthesized special reference standards of cyclopenta-fused PAH (CP-PAH) and ethynyl-substituted PAH. We have identified several of these CP-PAH and ethynyl-PAH in benzene droplet combustion products, using high pressure liquid chromatography (HPLC) and ultraviolet-visible (UV) absorption spectroscopy. Although one CP-PAH identified in these products - acenaphthylene - has previously been identified as a product of a variety of combustion systems, we have identified six additional CP-PAH and two ethynyl-PAH which have never before been unequivocally identified as the products of benzene pyrolysis or combustion: acephenanthrylene, aceanthrylene, cyclopent[hi]acephenanthrylene, cyclopenta[cd]fluoranthene, cyclopenta[cd] pyrene, dicyclopenta[cd, jk]pyrene, 2-ethynylnaphthalene, and 1-ethynylacenaphthylene. We present the corresponding UV absorption spectra obtained from the HPLC analysis of benzene droplet combustion products, and compare them to the UV absorption     

AM1 Treatment of Silacyclacenes

Semi-empirical molecular orbital treatment at the level of AM1 type has been performed on Hückel type silacyclacenes having arenoid rings (R) of 2-9. The first and second type cryptoannulenic effects are defined.     

SLIP EFFECT ON DIFFUSION OF CHEMICALLY REACTIVE SPECIES IN BOUNDARY LAYER FLOW OVER A VERTICAL STRETCHING SHEET WITH SUCTION OR BLOWING

In the present investigation, we study the effects of slip boundary condition on the diffusion of chemically reactive species in steady boundary layer flow of viscous incompressible fluid over a vertical stretching sheet with suction or blowing. The first-order chemical reaction is considered and wall concentration varies linearly along the sheet. The self-similar equations are obtained using similarity transformations and are solved numerically using shooting method. Our study reveals that due to the increase of diffusion parameter and blowing, the velocity increases, and it decreases with suction, Schmidt number, and reaction rate parameter. Importantly, for increase of slip parameter, the boundary layer thickness increases. In contrast, the concentration at a point increases only for increasing slip and blowing, while it decreases for increase of all other parameters.     

INFLUENCES OF INTERFACIAL CONVECTION AND PHYSICAL PROPERTIES OF DESICCANT SOLUTIONS ON THE MASS TRANSFER PERFORMANCE OF ABSORPTION SYSTEMS

In order to investigate the mass transfer phenomenon of the absorption of water vapor in desiccant solutions, a system of absorption cell was designed. The gradient in surface tension can result from the contact process between the desiccant solution and water vapor. This induced interfacial disturbance will affect the mass transfer performance. The experimental results demonstrate that the theoretical mass transfer coefficients predicted by boundary layer theory are less than those of the experimental values. In addition, the mass transfer performance of the absorption system can be enhanced by adding ethanol to the absorbent solutions. In order to describe the level of mass transfer performance affected by the interfacial convection resulting from the addition of ethanol, the enhancement factor was defined in this study. The enhancement factor is from 1.26 to 1.56 for adding ethanol to DEG (diethylene glycol) solution, and from 1.36 to 1.61 for adding ethanol to TEG (triethylene glycol) solution.