采用扫描电镜和图像分析表征帘式涂布涂层中的孔隙结构和粘土取向

造纸行业对高速帘式涂布非常感兴趣,因为帘式涂布可以不使用与网接触的机械计量设备而达到生产高涂布量的涂布纸和纸板的目的。该具有计量功能的涂布工艺避免了很多在计量过程中与高剪切相关的问题和由此带来的缺陷。而且,帘式涂布可以形成覆盖率良好且均匀的涂层。尽管越来越多工厂使用帘式涂布工艺,但对帘式涂布形成涂层的结构特征的研究却很少。在此次研究中,我们将会分析商业化生产的帘涂牛卡纸和纸板的涂层结构,并使用横截面图像分析技术来表征涂层结构。对帘式涂布纸的结构参数如孔隙尺寸分布、颗粒取向以及涂层厚度的均匀性进行了评价,并与传统的刮刀涂布和膜涂布纸进行了对比。结果表明,帘式涂布形成的涂层结构具有更松厚且更多孔等优点。粘土粒子在帘式涂层中分布更均匀,这也表明了帘式涂布具有良好的涂布覆盖率以及涂层厚度均匀性。     

Sensory Preference, Coating Evenness, Dustiness, and Transfer Efficiency of Electrostatically Coated Potato Chips

Barbeque, sour cream and onion, salt and vinegar, nacho cheese, and salsa seasonings were applied to potato chips at 0 and 25 kV. Sensory evaluation determined that electrostatically coated chips had better coating uniformity and were significantly preferred to nonelectrostatically coated samples. Electrostatic coating was also more even as measured by colorimetry. Particle size and evenness of coating did not significantly affect perceived flavor intensity. Electrostatic coating significantly increased transfer efficiency and decreased dust over nonelectrostatic coating. Particle size and flowability can be used to predict transfer efficiency and dustiness. Chargeability was also important for electrostatic transfer efficiency. Particle size was the most important factor overall.     

Food Powder Characteristics Important to Nonelectrostatic and Electrostatic Coating and Dustiness

ABSTRACT: Corn starch, maltodextrin, powdered sugar, cellulose, soy flour, corn flour, wheat flour, cocoa, nonfat dry milk, and salt were coated at 0, 19, and 25 kV using corona particle charging. Particle size, powder charge, density, and flow characteristics (flow index, cohesiveness, angle of repose, Hausner ratio) were correlated to coating efficiency and dustiness. Nonelectrostatic coating efficiency improved with large particle size, small powder charge, and low cohesiveness. Electrostatic coating at 25 kV improved with small particle size, low flow index, and high particle density. Dustiness decreased with large particle size-particle density interaction, high flow index, and low cohesiveness. Electrostatics improved coating efficiency 68% and decreased dustiness 65% (excluding largest salt).     

Modelling coating quality in fluidised bed coating: Spray sub-model

Fluidised beds are widely used in industrial applications for the coating of particles. Little research has been performed in developing a model that is able to predict the quality of the coating process in terms of the coating thickness and uniformity and the occurrence of unwanted side-effects, including agglomeration, attrition and spray loss. The quality of the coating process in a fluidised bed is largely determined by the spray characteristics and the particle motion. As a first step in the development of a new model for the coating process in a top-spray fluidised bed, an accurate spray sub-model that describes the movement and the heat and mass transfers of the droplets in the coating process was created and experimentally validated.     

Corona Compared with Triboelectric Charging for Electrostatic Powder Coating

ABSTRACT:  The purpose of this research was to compare electrostatic and nonelectrostatic coating and determine the improvement between corona and triboelectric charging systems. Graham crackers were coated with food powder at 0, −50, or −95 kV or by tribocharging with teflon or nylon. Five sizes of sucrose from 13 to 138 μm were coated onto the crackers to determine the effect of particle size on coating efficiency. Three proteins, three carbohydrates, and one salt between 35 and 58 μm were analyzed to determine the effect of composition. Electrostatics improved transfer efficiency (TE) up to 27%, adhesion up to 40%, and reduced dust up to 99% over nonelectrostatic coating. Particle size and composition significantly affected the improvement produced by each charging method. As particle size increased, nonelectrostatic TE and adhesion increased, while dust decreased. Electrostatic TE increased and leveled off and adhesion and dust decreased with increasing particle size. Generally, corona TE, adhesion, and dust reduction was the highest, followed by teflon triboelectric, nylon triboelectric, and nonelectrostatic coating. For proteins, teflon produced higher charge to mass, TE, and adhesion than nylon. Although the corona system was most efficient, the teflon triboelectric system produced comparable results for some powders and may be necessary to produce a thick coating while minimizing back ionization and alleviating Faraday Cage effects.     

颜料的粒径对无光泽喷墨打印纸色彩再现性的影响

硅胶由于具有唯一的形态,能提供内部孔隙和填充孔隙,从而使液体油墨快速分散进入涂布层,常用作优质的无光泽喷墨打印涂布纸的涂布颜料。本课题主要研究不同粒径的胶体二氧化硅和传统颜料(研磨碳酸钙)对喷墨打印纸色彩再现性的影响。     

铜版纸水性上光工艺对上光质量的影响

为了研究铜版纸水性上光涂布工艺对印品质量的影响,得到最佳的涂布工艺参数,使用IGT印刷适性仪在一定印刷条件下对铜版纸实地打样,分别在不同的涂布速度与涂布厚度下,对各印刷样张进行水性光油上光涂布,通过测试各样张的光泽度和耐折度,比较不同工艺条件下上光前后印品光泽度和耐折度的变化,探讨涂布速度、涂布厚度对水性上光质量的影响。结果表明,涂布速度和涂布厚度与印品的光泽度和耐折度有关。上光印品的光泽度和耐折度会随着涂布速度和涂布厚度的增大而增大,其增量有最大值。合理匹配上光工艺的这两个条件,能够获得最佳上光工艺参数。     

Soot Aging from OH-Initiated Oxidation of Toluene

We have conducted laboratory experiments to investigate the impacts of secondary organic aerosol formation on soot properties from OH-initiated oxidation of toluene. Monodisperse soot particles are exposed to the oxidation products of the OH-toluene reaction in an environmental chamber, and variations in particle size, mass, organic mass faction, morphology, effective density, hygroscopicity, and optical properties are simultaneously determined by an integrated aerosol analytical system. The thickness of the organic coating, correlated to reaction time and initial reactant concentrations, is shown to largely govern the particle properties. With the development of organic coating, the soot core is changed from a highly fractal to compact form, evident from the measured effective density and dynamic shape factor. The organic coating increases the particle hygroscopicity, and further exposure of coated soot to elevated relative humidity results in a more spherical particle. The single scattering albedo and scattering and absorption cross sections are also enhanced with the organic coating. Our results suggest that the oxidation products of anthropogenic pollutants alter the composition and properties of soot particles and lead to increased particle density, hygroscopicity, and optical properties, considerably enhancing their impacts on air quality, climate forcing, and human health.     

颜料窄粒径分布对涂层性能影响的研究

研究了颜料的不同粒径分布,特别是窄粒径分布对涂布纸涂层性能的影响.结果表明窄粒径分布能增加涂层性能,颜料粒子的窄粒径堆砌结构形成的湿涂布层的微粒堆积密度较小,形成更开放式的滤饼层,导致快速脱水,具有较高的湿孔隙率,较低的不动点固含量,较高的光散射系数,粒子的均一性也赋予涂层具有较好的平滑度和光泽度.     

乙基纤维素微胶囊化膨化小麦胚芽粉品质研究

本试验采用膨化胚芽粉为芯材,0.00%、2.00%、2.75%、3.50%、4.25%和5.00%浓度的乙基纤维素－乙醇溶液为壁材溶液,使用空气悬浮法（流化床包衣法）,包衣方式为底喷的方式制得微胶囊样品。通过对不同浓度乙基纤维素－乙醇溶液微胶囊化样品各项指标的研究,即水分含量、溶解度、容积密度、流动性、包含率、粒径分布、感官评价、表面形态结构和加速储藏条件下的脂肪酸值的变化,综合评价样品品质,得出浓度4.25%为乙基纤维素－乙醇溶液微胶囊化膨化胚芽粉的最佳浓度。4.25%浓度乙基纤维素－乙醇溶液微胶囊化样品水分含量为5.59%,溶解度为30.87%,容积密度为51.61 g/100 mL,休止角为29.71°,包含率为98.14%,粒径分布均匀,结构完整,表面无裂纹或破损现象,无不良气味。此外,在加速储藏条件下,30 d内脂肪酸值增加量较小。     

Transport behavior of selected nanoparticles with different surface coatings in granular porous media coated with Pseudomonas aeruginosa biofilm

Well-controlled laboratory column experiments were conducted to understand the influence of Pseudomonas aeruginosa (P. aeruginosa) biofilms on the transport of selected engineered nanoparticles (ENPs) in granular porous media representative of groundwater aquifers or riverbank filtration settings. To understand the importance of particle size on retention in the biofilm-coated granular (quartz sand) matrix, column experiments were carried out using nanosized (20 nm) and micrometer-sized (1 μm) sulfate-functionalized polystyrene latex particles (designated as 20 nSL and 1 mSL, respectively). Additional experiments conducted with nanosized (20 nm) carboxyl-modified latex particles (20nCL) and carboxyl-modified CdSe/ZnS quantum dots (QDs) provide information on the influence of particle surface chemistry on retention. Biofilm grown on the surface of the sand was characterized by total biomass quantification, confocal laser scanning microscopy (CLSM), and electrokinetic analysis. All four particles exhibit increased retention in the biofilm-coated packed bed: e.g., the attachment efficiency (α) of the 1 mSL particle increases from 0.40 to 1.7, whereas α for the 20 nSL particle increases from 0.04 to 0.10 in the biofilm-coated system. Particle surface chemistry can also influence the affinity of the ENPs for the biofilm coating as revealed by the greater attachment of the 20 nSL particle onto the biofilm-coated sand (α = 0.10) than its carboxylated counterpart (α = 0.04). Column experiments conducted using sand coated with growth medium (LB) or extracellular polymeric substances (EPS) extracted from P. aeruginosa biofilms further reveal that particle surface chemistry influences the interaction between the different ENPs and these coated sand surfaces. Namely, coating of sand surfaces with LB medium or bacterial EPS does not affect the transport of the sulfonated nanoparticle, but the LB coating leads to decreased retention of the carboxylated latex nanoparticle. Furthermore, our results show that EPS coatings are not necessarily good surrogates for biofilm-coated sand. Electrokinetic characterization of the clean and coated sand surfaces also reveals that the extent of particle retention is not controlled by electrical double layer interactions. Future studies should thus be aimed at improving our understanding of the fundamental mechanisms (both colloidal and noncolloidal) governing nanoparticle transport and fate in biofilm-laden granular aquatic environments.     

EFFECT OF BREADING PARTICLE SIZE ON COATING ADHESION IN BREADED, FRIED CHICKEN BREASTS

The effect of particle size on coating adhesion was measured for battered chicken breasts. Bread crumbs were separated into small (≤ 250 μm), medium (250 μm-850 μm), and large (> 850 μm) particles. Chicken breasts were battered, breaded, and deep-fat fried for 240 s at 160C. Fried products were analyzed for coating adhesion, moisture content, and yield parameters. Coating adhesion was highest in coatings formed from small particle size breading, and lowest in those made from large particle size breading. Chicken breasts coated using small particle size breading had higher moisture in the surface region of the meat as well as in the coating. SEM of the coatings showed greater merging between the breading and the batter with decreasing breading particle size. No significant differences were observed in coating pickup, cooking loss, or yield between samples coated with different particle size breading.     

FLUIDIZED-BED SYSTEM FOR WHEY PROTEIN FILM COATING OF PEANUTS

Complete peanut‐surface coverage and strong adhesion are necessary for whey protein‐based oxygen barrier coatings to be totally effective in reducing the oxidative rancidity of peanuts. Peanuts coated with a fluidized‐bed coating system attained practically complete coverage, and coating efficiency results were consistent and reproducible. Addition of surfactant to the coating solution improved whey protein coating efficiency on blanched/roasted peanuts coated with a bench‐scale fluidized‐bed coating system. A lower level of surfactant addition to the coating solution was required to attain complete coverage, compared with previous studies on dip coating and pan coating of peanuts. Addition of surfactant to the coating solution and peanut preroughening both imparted good coating adhesion for fluidized‐bed‐coated peanuts. Compared with pan coating, fluidized‐bed coating required application of a greater amount of coating solution because of the loss of coating solution to the fluidized‐bed column wall during spraying. Overall, fluidized‐bed coating required a shorter processing time and provided the peanuts with better coating efficiency and adhesion. These results suggest that a fluidized‐bed coating system is a viable alternative coating process for whey protein coating of peanuts.     

小麦粉粒度研究综述

小麦粉粒度是小麦粉的一个重要物理参数,它对小麦粉以及面制食品的品质产生很大的影响。小麦粉粒度的分布与小麦的品质和研磨方法有关。当小麦粉粒度变化时,小麦粉的组成成分以及物理特性也会发生变化,从而对面制品的品质产生影响。阐述了小麦粉粒度、小麦粉粒度分布以及当小麦粉粒度变化时,小麦粉的组成成分的变化等几个方面内容,同时介绍了小麦粉粒度的测定方法、小麦粉粒度在小麦硬度研究方面的应用和小麦粉粒度对面制品品质的影响。     

Particle size distribution and chemical composition of total mixed rations for dairy cattle: Water addition and feed sampling effects

Four dairy farms were used to determine the effects of water addition to diets and sample collection location on the particle size distribution and chemical composition of total mixed rations (TMR). Samples were collected weekly from the mixing wagon and from 3 locations in the feed bunk (top, middle, and bottom) for 5 mo (April, May, July, August, and October). Samples were partially dried to determine the effect of moisture on particle size distribution. Particle size distribution was measured using the Penn State Particle Size Separator. Crude protein, neutral detergent fiber, and acid detergent fiber contents were also analyzed. Particle fractions 19 to 8, 8 to 1.18, and <1.18 mm were judged adequate in all TMR for rumen function and milk yield; however, the percentage of material >19 mm was greater than recommended for TMR, according to the guidelines of Cooperative Extension of Pennsylvania State University. The particle size distribution in April differed from that in October, but intermediate months (May, July, and August) had similar particle size distributions. Samples from the bottom of the feed bunk had the highest percentage of particles retained on the 19-mm sieve. Samples from the top and middle of the feed bunk were similar to that from the mixing wagon. Higher percentages of particles were retained on >19, 19 to 8, and 8 to 1.18 mm sieves for wet than dried samples. The reverse was found for particles passing the 1.18-mm sieve. Mean particle size was higher for wet than dried samples. The crude protein, neutral detergent fiber, and acid detergent fiber contents of TMR varied with month of sampling (18-21, 40-57, and 21-34%, respectively) but were within recommended ranges for high-yielding dairy cows. Analyses of TMR particle size distributions are useful for proper feed bunk management and formulation of diets that maintain rumen function and maximize milk production and quality. Water addition may help reduce dust associated with feeding TMR.     

Electrostatic powder coating of foods – State of the art and opportunities

Edible coatings and incorporation of active ingredients can improve food quality (appearance, taste, flavours, and increased shelf life). In this paper, specific emphasis is given to electrostatic application of powder coatings that is known for high transfer efficiency and even coating. This application technique has the potential to reduce excessive use of coating material (up to 68%) and minimise dust release (up to 84%) to the environment. Different parameters (e.g. powder particle size) are discussed that influence powder coating quality and efficiency for both non-electrostatic and electrostatic powder application. Typical food processing systems are reviewed that can be combined with electrostatic powder coating. Finally, an overview of electrostatically coated food products and a short outlook of electrostatic powder coating of foods are given.     

Confectionery coating with an electrohydrodynamic (EHD) system

In the confectionery coating industry, hard butters are frequently used as cocoa butter replacers. An electrohydrodynamic (EHD) system, which forms fine droplets with a relatively narrow size distribution, may be beneficial in confectionery coating to produce more even coverage. The objective of this study was to determine the effect of lecithin content and fat type on electrical resistivity and apparent viscosity, and the effect of these variables under EHD (25kV) and non-EHD coating on droplet size, width of coating area, thickness, and minimum flow rate to produce complete coverage. Total of 3 different types of fat were used: cocoa butter, cocoa butter equivalent, and lauric butter. As lecithin content increased, resistivity and apparent viscosity decreased, except all samples showed a local apparent viscosity minimum at 0.5% lecithin. EHD coating was more efficient than non-EHD as a smaller droplet size and thinner coating was formed. Due to repulsive forces between the like-charges on the droplets during EHD, it spread over wider areas which lead to a higher minimum flow rate to get complete coverage. Under EHD, increasing resistivity significantly increased the droplet size, but only at the highest resistivities. There was no correlation between resistivity and droplet size or width of coating under non-EHD. The width of coating under EHD decreased significantly as resistivity increased. Thickness and minimum flow rate to produce complete coverage, significantly correlated to resistivity, for EHD coating, and to apparent viscosity, for 2 of the 3 fat types during both EHD and non-EHD. PRACTICAL APPLICATION: Electrohydrodynamic (EHD) spraying offers great potential improvement to the food industry especially in the confectionery area. From the quality point of view, EHD offers greater and more complete coverage than non-EHD coating. From the economic point of view, lower cost can be achieved for coated food because during EHD, smaller droplet size and thinner coating is produced.     

片状碳酸钙的制备及其在造纸涂布中的应用

以氧化钙、二氧化碳为主要原料制备出具有晶形好、粒径分布范围小,平均粒径小等特点的片状碳酸钙,工艺条件为w(Cao):w(H2O)=1:5,V(CO2):V(空气)=1:2.采用5种不同比例的配方将此片状碳酸钙应用于涂布实验,主要考察了片状碳酸钙用量对纸张主要物理性能的影响.涂布实验表明:纸的平滑度、透气度,油墨吸收性及拉毛强度等物理性能均得到显著提高.     

Physical Properties Important to Electrostatic and Non electrostatic Powder Transfer Efficiency in a Tumble Drum

ABSTRACT: Popcorn was oiled and coated in a tumble drum nonelectrostatically and electrostatically with sugar, cornstarch, salt, cellulose, maltodextrin, all-purpose flour, whole-wheat flour, or soy flour. Particle size, density, flowability, and chargeability were correlated to transfer efficiency using regression analysis. Of the various methods to measure chargeability, charge-to-mass and adhesion improvement were the most significant. For nonelectrostatic coating, small, dense, free-flowing powders were most efficient. Small, free-flowing highly charging powders were most efficient for electrostatic coating. Percent improvement was the highest for the least efficient powders. The greatest benefit with electrostatic coating was for low density, highly charging powders with no effect of size.     

汽车座椅用调温纺织品的开发

调温纺织品是将相变材料与纤维和纺织品制造技术相结合开发出的一种新型功能性产品。以液体石蜡作为芯材料,合成了直径大约3.0μm的聚脲型相变微胶囊,并用涂层方法制备了汽车座椅用相变调温纺织品。测试了微胶囊的形貌、粒径及粒径分布,探讨了涂层工艺的各影响因素,分析了调温纺织品的物理性能和热性能。