The Effect of Plasticizers on Mechanical Properties and Water Vapor Permeability of Gelatin-Based Edible Films Containing Clay Nanoparticles

The effects of glycerol and sorbitol as two plasticizers on mechanical properties, water vapor permeability, thermal properties, color and capability of heat sealing of gelatin films (of phytophagous fish, bovine gelatin with high gel-forming ability, and bovine gelatin with low gel-forming ability) containing clay nanoparticles were studied in this research. For this purpose, 6 × 2 × 3 factorial experiments using the completely randomized design and comparison of the means at 95% confidence level (α = 0.05) were performed. Higher concentrations of plasticizers increased percentage elongation to the breaking point. When glycerol concentration was raised to over 20%, flexibility of the layers improved but their water vapor permeability increased. The minimum passage of water vapor was that of fish-skin gelatin films containing clay nanoparticles and 30% sorbitol, and the maximum that of bovine gelatin films with high gel-forming ability which contained nanoparticles but no plasticizers (p 0.05). All samples had heat sealing capability, and fish-skin gelatin films containing clay nanoparticles had better heat sealing capability compared with the other samples so that fish-skin gelatin films containing clay nanoparticles with 25% glycerol and 5% sorbitol had the highest flexibility and tensile strength, and remained attached to where they were heat sealed. Electron microscope images showed that films without plasticizers had uniform surfaces, but that samples containing glycerol at concentrations of over 0.20 g/g gelatin exhibited cavities between gelatin chains and that water vapor permeability in gelatin films containing clay nanoparticles.

The PVT Properties Calculation of Water by BWR Equation

A series of thermodynamic functions are applied to generalize the Benedict-Webb-Rubin equation. The method has been successfully applied to this equation, which reduced the constants of BWR equation from eight to one. The calculation of PVT behavior of water over the entire thermodynamic surface is successful with satisfactory deviation.

Enhancing comprehension of water vapor on adsorption performance of VOC on porous carbon materials and its application challenge

Volatile organic compounds(VOC)have been proven to cause considerable harm to both the ecological environment and human health.Anthropogenic VOC emissions are primarily generated by the industrial sector.The utilization of porous carbon as an adsorbent has emerged as an effective method for the efficient removal of VOC from industrial sources.However,during the actual production processes,VOC exhaust gases are often mixed with water vapor,which poses challenges for adsorption purification.This review provides a comprehensive overview of the remarkable advancements in various carbon materials in terms of their ability to adsorb both VOC and water vapor.Additionally,it systematically summarizes the influence of surface groups on adsorbents and the molecular properties of VOC on their adsorption by carbon materials.Furthermore,this review introduces the mechanism underlying adsorption-adsorbent interactions and discusses the construction of models for adsorbing water vapor and VOC.The challenges associated with the application of carbon materials for VOC adsorption in humid environments are also addressed.This review aims to offer theoretical and technical guidance for the effective purification of moist VOC waste gases emitted from industrial sources,thereby achieving precise control of VOC emissions.

MCSPT-A MODIFIED HARD-SPHERE THREE-PARAMETER EQUATION OF STATE FOR THERMODYNAMIC PROPERTIES OF PURE COMPOUNDS

The hard - sphere three - parameter equation of state(CSPT) proposed in the previous paper(Li et al. 1991) was modified by a new temperature relation for the pseudo-critical compressibility ξc and the temperature correction factor α(Tr) of the attractive parameter. Vapor pressures and saturated liquid densities of 105 pure compounds were calculated by the modified version. Results show that correlations of saturated properties at low reduced temperatures and thermodynamic properties in the vicinity of critical region were significantly improved. Furthermore, characteristic parameters of this modified version were generalized by acentric factor ω and critical compressibility Zc to predict saturated liquid densities of 72 polar substances and the latent heat of vaporization for 151 substances including strongly polar compounds with satisfactory results.

Thermodynamic Fit Functions of the Two-Phase Fluid and Critical Exponents

Two-phase fluid properties such as entropy, internal energy, and heat capacity are given by thermodynamically defined fit functions. Each fit function is expressed as a temperature function in terms of a power series expansion about the critical point. The leading term with the critical exponent dominates the temperature variation between the critical and triple points. With β being introduced as the critical exponent for the difference between liquid and vapor densities, it is shown that the critical exponent of each fit function depends (if at all) on β. In particular, the critical exponent of the reciprocal heat capacity c﹣1 is α=1-2β and those of the entropy s and internal energy u are?2β, while that of the reciprocal isothermal compressibility?κ﹣1T is γ=1. It is thus found that in the case of the two-phase fluid the Rushbrooke equation conjectured α +?2β + γ=2 combines the scaling laws resulting from the two relations c=du/dT and?κT=dlnρ/dp. In the context with c, the second temperature derivatives of the chemical potential μ and vapor pressure p are investigated. As the critical point is approached, ﹣d2μ/dT2 diverges as c, while?d2p/dT2 converges to a finite limit. This is explicitly pointed out for the two-phase fluid, water (with β=0.3155). The positive and almost vanishing internal energy of the one-phase fluid at temperatures above and close to the critical point causes conditions for large long-wavelength density fluctuations, which are observed as critical opalescence. For negative values of the internal energy, i.e. the two-phase fluid below the critical point, there are only microscopic density fluctuations. Similar critical phenomena occur when cooling a dilute gas to its Bose-Einstein condensate.

The effect of humidity on the CO_2/N_2 separation performance of copolymers based on hard polyimide segments and soft polyether chains:Experimental and modeling

In this work, we studied two copolymers formed by segments of a rubbery polyether（PPO or PEO） and of a glassy polyimide（BPDA-ODA or BKDA-ODA） suitable for gas separation and CO2 capture. Firstly, we assessed the absorption of water vapor in the materials, as a function of relative humidity（R.H.）, finding that the humidity uptake of the copolymers lies between that of the corresponding pure homopolymers values.Furthermore, we studied the effect of humidity on CO2 and N2 permeability, as well as on CO2/N2 selectivity, up to R.H. of 75%. The permeability decreases with increasing humidity, while the ideal selectivity remains approximately constant in the entire range of water activity investigated. The humidity-induced decrease of permeability in the copolymers is much smaller than the one observed in polyimides such as Matrimid? confirming the positive effect of the polyether phase on the membrane performance.Finally, we modeled the humidity-induced decrease of gas solubility, diffusivity and, consequently, permeability, using a suitable approach that considers the free volume theory for diffusion and LF model for solubility. Such model allows estimating the extent of competition that the gases undergo with water during sorption in the membranes, as a function of the relative humidity, as well as the expected reduction of free volume by means of water molecules occupation and consequent reduction of diffusivity.

Effects of Calcium Ions on Thermodynamic Properties of Mixed Bilirubin/Cholesterol Monolayers

The mixed monolayer behavior of bilirubin/cholesterol was studied through surface pressure-area （π-A） isotherms on aqueous solutions containing various concentrations of calcium ions. Based on the data of π-A isotherms, the mean area per molecule, collapse pressure, surface compressibility modulus, excess molecular areas, free energy of mixing, and excess free energy of mixing of the monolayers on different subphases were calculated. The results show an expansion in the structure of the mixed monolayer with Ca^2＋ in subphase, and non-ideal mixing of the components at the air/water interface is observed with positive deviation from the additivity rule in the excess molecular areas. The miscibility between the components is weakened with the increase of concentration of Ca^2＋ in subphase. The facts indicate the presence of coordination between Ca^2＋ and the two components. The mixed monolayer, in which the molar ratio of bilirubin to cholesterol is 3：2, is more stable from a thermodynamic point of view on pure water. But the stable 3：2 stoichiometry complex is destroyed with the increase of the concentration of Ca^2＋ in subphase. Otherwise, the mixed monolayers have more thermodynamic stability at lower surface pressure on Ca^2＋ subphase.

The Influence of Two Natural Reinforcement Fibers on the Hygrothermal Properties of Earthen Plasters in Mogao Grottoes of China

Murals in Mogao Grottoes consist of three parts:support layer,earthen plasters and paint layer.The earthen plasters play a key role in the preservation of murals.It is a mixture of Dengban soil,sand,and plant fiber.Two different natural fibers,hemp fiber and cotton fiber,were reinforced to earthen plasters in the same percentage to evaluate the influence on hygrothermal performance.The two types of earthen plasters were studied:one containing hemp fiber in the fine plaster(HFP)and the other containing cotton fiber in the fine plaster(CFP).Specific heat capacity,dry thermal conductivity,water vapor permeability,and sorption isotherms were investigated.The results showed that the difference between two natural fibers has much more impact on the hygric properties(water vapor permeability and sorption isotherms)of earthen plasters than on their thermal performance(specific heat capacity and dry thermal conductivity).The CFP with higher density has higher thermal conductivity than the HFP with lower density.But no significant differences of specific heat capacity were observed.Compared with HFP,CFP used in murals can reduce the rate of water transfer and prevent salt from transferring water to the mural surface.The overall findings highlight that all these features of CFP are beneficial to the long-term preservation of murals.The study of the earthen plasters in Mogao Grottoes is of general significance,and the measured properties can be used to obtain coupled heat and moisture analysis of the earthen plasters and to dissect the degradation mechanism of murals.

中昆仑山北坡水汽含量的计算及其特征分析

干旱区水汽变化影响区域水资源系统的结构和演变,基于2020年1月—2022年12月中昆仑山北坡地区4个地基GPS遥感大气可降水量资料(GPS-PWV)、2个探空站观测资料和108个地面气象观测站逐时水汽压资料,利用一元线性拟合方法建立了适用于中昆仑山北坡地区的大气水汽含量(W-PWV)和地面水汽压计算模型(W-e)并对计算结果进行评估,分析了中昆仑山北坡地区东段、中段、西段W-PWV的时空分布特征及降水开始时刻与W-PWV峰值的关系。结果表明:(1)W-PWV年平均高值区位于研究区西段,中段次之,东段沙漠南缘W-PWV最低。海拔高度大于1500 m测站W-PWV随高度升高逐渐减少。夏季地面气象观测站平均W-PWV是春、秋季的2倍左右;(2)研究区W-PWV月变化具有单峰型特征,其中海拔高度1300~1500 m测站的W-PWV在7月和8月达到峰值,其余测站的W-PWV在8月达到峰值,海拔低于2000m和高于2000m测站W-PWV分别在夜间和白天维持较高值;(3)水汽含量模型计算的测站W-PWV与降水开始时刻有较好的对应关系,降水前各站W-PWV均存在不同程度跃变过程,降水过程前1~2h内W-PWV峰值达到测站W-PWV月平均值的1.5倍以上。

热水化学驱体系与稠油组分间相互作用及其理论模拟研究

为了探究温度和聚合物化学剂对稠油性质的影响,通过扫描电子显微镜、傅里叶变换红外光谱仪以及流变仪对稠油组分进行了分析.由扫描电子显微镜观察到沥青质表面形态不规则,胶质表面粗糙且具有孔道结构.傅里叶变换红外光谱检测出3种稠油组分具有芳香烃的特征吸收峰.通过流变性能测试研究了聚合物化学剂的投加量、矿化度、温度和pH值对稠油流变性能和体相结构特性的影响.结果表明,聚合物投加量对稠油的储能模量和损耗模量有显著影响,而矿化度的增加则增强了稠油的复数黏度,酸性和碱性条件下稠油的黏弹性较中性条件更强.通过理论计算研究发现,添加聚合物化学剂可以降低稠油的黏度,在较高的温度下效果更加显著.沥青质与聚合物化学剂之间的相互作用最强,其次为胶质,与油分的相互作用最弱.聚合物化学剂对稠油组分的径向分布函数无明显影响,主要影响界面处的稠油组分.聚合物化学剂与沥青质可以形成氢键,添加聚合物化学剂后,沥青质内部的氢键数量减少,与聚合物化学剂之间的氢键数量增加.温度升高会减少氢键数量,尤其是沥青质与聚合物化学剂之间的氢键.

不同温度下斜叶桉木材吸湿、解吸等温线与热力学性质

近年来斜叶桉(Eucalyptus obliqua)木材广受国内市场欢迎,需求量大,但尚无高效可行的常规干燥工艺,需对其吸湿性及热力学性质进行深入研究。本文利用恒温恒湿箱法研究了斜叶桉在不同温度下(30℃、45℃、60℃、75℃)的等温吸湿、解吸特性,并通过GAB和H-H模型对吸湿和解吸等温线进行拟合,对吸湿滞后现象,以及有效比表面积S、净等量吸湿热Q_(st)、总润湿热W_(0)、微分熵ΔS、吉布斯自由能变ΔG、扩张压力Φ、焓熵补偿等热力学性质进行了分析。结果表明,斜叶桉木材的吸湿和解吸等温线为Ⅱ型,且GAB和H-H模型均适用于木材-水分体系(R^(2)大于0.999)。恒定温度下,试样平衡含水率(EMC)随水分活度的增加而增加。恒定水分活度下,EMC和吸湿滞后程度均随温度的升高而降低。有效比表面积随着温度升高而降低。总体上,吸湿过程净等量吸湿热和微分熵为负值,而解吸过程为正值,净等量吸湿热和微分熵的大小均随EMC先增大后减小,直至趋近于0。解吸过程总润湿热绝对值为83.7k J/mol,远大于吸湿过程的32.2k J/mol。等速温度和平均调和温度不一致,焓熵补偿理论成立。吸湿、解吸过程均为焓驱动,不同的是吸湿为自发过程,解吸为非自发过程。扩张压力会随着水分活度的升高而升高,吸湿过程中,温度对于扩张压力的影响无明显规律,而在解吸过程中,扩张压力随温度的升高而升高。

水氧化还原反应中电极电势的计算和讨论

计算电极电势是电化学的必备技能。目前物理化学教材中,一般只给出了酸性条件下部分物质的标准电极电势(φ^(Θ)),以及如何利用Nernst方程由φ^(Θ)计算电极电势(φ)。教材中对于碱性条件下φ_(B)^(Θ)没有涉及,学生对φ_(B)^(Θ)不甚理解,乃至在由φ_(B)^(Θ)计算φ时可能得到错误的结果和结论。本文以水(H_(2)O)氧化还原反应为例,从物质的标准生成Gibbs自由能变(△_(f)G_(m)^(Θ))出发计算φ^(Θ)和φ_(B)^(Θ),结合酸(或碱)性条件下反应物种的分析,利用Nernst方程计算不同pH下的φ,给出φ–pH图。此外,还讨论了热力学同位素效应对φ^(Θ)和φ的影响。这可为作为相关教学和科研的参考。

改性复合生物降解地膜的制备及玉米田间应用评价

[目的]使用生物降解地膜替代传统聚烯烃地膜已成为治理农业白色污染的一项重要技术。主流材料聚对苯二甲酸-己二酸丁二醇酯(PBAT)在制备生物降解地膜时表现出优异的成膜性能,但其水蒸气阻隔性较差,导致降解时间短,限制了其在农用地膜方面的应用。因此,需要进行改性研究以解决PBAT生物降解地膜在拉伸强度、水蒸气阻隔性能和降解期等方面的不足。[方法]本研究将PA6(尼龙6)与PBAT相结合,使用高分子共混法制备PBAT/PA6改性生物降解地膜。该方法制备的生物降解地膜有效地将PBAT与PA6融合在一起,电子显微镜测试表明,混合地膜的表面和横截面均无明显缺陷。于2023年春玉米生长季,在北京顺义地区农田设置不同覆膜处理(PBAT地膜覆盖,PBAT/PA6-10地膜覆盖,PE地膜覆盖,不覆膜处理即CK)的田间对比试验,研究土壤温度、地膜田间降解情况、春玉米产量及其构成因素的变化。[结果]与纯PBAT生物降解地膜相比,本研究所开发的生物降解地膜的拉伸强度提高了约2.7倍,水蒸气阻隔性能提高了79.44%,功能期延长了30 d。玉米作物田间试验表明,改性生物降解地膜更适合农业生产,因其可提高隔热性和保湿性,使玉米产量较纯PBAT地膜提高7.03%,接近传统聚乙烯地膜产量。[结论]将PA6与PBAT材料相结合,开发出了一种新型复合生物降解地膜PBAT/PA6。PA6的加入与PBAT反应形成酰胺键使其整体结构具有稳定性,所制备复合生物降解地膜表面和截面形貌良好,内部无明显孔洞,较PBAT地膜表面更光滑,同时在力学性能和水蒸气阻隔性能上较纯PBAT地膜有显著提升,在田间试验过程中,复合生物降解地膜PBAT/PA6具有优秀的耐降解性能,延长了覆盖时间,并较纯PBAT地膜显著提高春玉米的产量。

水热老化对天然气发动机三元催化转化器性能影响的试验研究

利用水热老化试验装置开展了催化剂小样的水热老化试验,分析了催化剂在水热老化前后起燃性能的变化规律,利用X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)、X射线衍射(X-ray diffraction, XRD)、N_2吸脱附与透射电子显微镜(transmission electron microscopy, TEM)等测试方法研究了老化温度和老化气氛(水含量)对催化剂活性、表面化学状态及微观结构的影响。试验结果表明,老化温度对催化剂理化特性的影响较大,随着老化温度的提高,催化剂的氧空位含量减少,储氧能力下降,助剂的粒径变大,比表面积变小,孔径变大,催化剂活性降低;老化气氛中水含量的变化对催化剂理化特性的影响较小,当水含量为10%时,催化剂的活性最高,此时催化剂的储氧能力较高,比表面积最大,表明适宜的水热老化有利于催化剂性能提升。

海藻酸钠包装膜的性能提升研究进展

海藻酸钠是褐藻中一种大量存在的多糖类化合物,低热无毒、生物相容性好、可降解,具有良好的增稠性、成膜性及稳定性等特点,因此可作为环境友好型食品保鲜材料代替传统塑料保鲜膜。但是海藻酸钠膜存在机械性能、抗水性和抑菌性能较差等缺点,限制了其在食品包装领域的应用。大量研究表明,通过添加不同物质可以显著改善海藻酸钠成膜后的性能。本文综述了改善海藻酸钠膜拉伸强度、断裂伸长率、水蒸气透过率和抑菌性等性能提升的研究进展,分析了各物质之间的相互作用及对复合膜性能的影响,并对目前海藻酸钠膜存在的问题和发展前景进行了总结与展望,以期为海藻酸钠膜在食品包装领域的研究和应用提供参考。

药品及食品包装用聚乙烯膜阻隔性能研究

目的 研究不同厚度低密度聚乙烯膜与高密度聚乙烯膜的氧气透过量和水蒸气透过量的变化情况,分析膜厚度对氧气透过量和水蒸气透过量的影响,为药品包装及食品包装在厚度、材质选择方面提供依据和指导。方法 分别采用压差法和红外法对不同厚度的聚乙烯膜进行氧气透过量和水蒸气透过量的测试。结论 氧气透过量随聚乙烯薄膜的增加而降低,水蒸气透过量随聚乙烯薄膜的增加而降低。相同厚度的膜,高密度聚乙烯膜的氧气透过量和水蒸气透过量均低于低密度聚乙烯膜。不同厚度不同材质的聚乙烯膜氧气透过量和水蒸气透过量不同。

Effects of water vapor in high vacuum chamber on the properties of HfO_2 films

The influence of water vapor content in high vacuum chamber during the coating process on physical properties of HfO2 films was investigated. Coatings were deposited on BK7 substrates by electron beam evaporation and photoelectric maximum control method. An in situ residual gas analyzer （RGA） was used to monitor the residual gas composition in the vacuum chamber. The optical properties, microstructure, absorption and laser-induced damage threshold （LIDT） of the samples were characterized by Lambda 900 spectrophotometer, X-ray diffraction （XRD）, surface thermal lensing （STL） technique and 1064-nm Qswitched pulsed laser at a pulse duration of 12 ns respectively. It was found that a cold trap is an effective equipment to suppress water vapor in the vacuum chamber during the pumping process, and the coatings deposited in the vacuum atmosphere with relatively low water vapor composition show higher refractive index and smaller grain size. Meanwhile, the higher LIDT value is corresponding to lower absorbance.

Surfactant-Assisted Poly(lactic acid)/Cellulose Nanocrystal Bionanocomposite for Potential Application in Paper Coating

The current article addresses a new strategy for the preparation of polylactic acid/cellulose nanocrystal(PLA/CNCs)nanobiocomposite films with improved structural morphology,mechanical and barrier properties for food packaging applications.The addition of hexadecyltrimethylammonium bromide(CTAB)and sodium lauryl sulfate(SLS)as cationic and anionic surfactants respectively,was found to play a crucial role in preventing re-aggregation of the CNCs during drying and improving the dispersion of CNCs in the PLA.The coated paper was characterized using mechanical tests,water vapor permeability(WVP),X-ray diffraction(XRD),scanning electron microscopy(SEM)and air permeability.The results showed that the paper coated with PLA containing 7.5%CNCs and 0.15%CTAB based on weight of PLA,gives the highest measured paper properties,where an increase in tensile strength(+133%),Young’s modulus(+309%),tear index(+183%),burst(+60.8)and a decrease in air permeability(−92%)was obtained.

Study of Hydrophilic Properties of Polysaccharides

In this research,the structural characteristics,specific surface area,sorption of water vapor,and wetting enthalpy of various polysaccharides(cellulose,hemicelluloses,starch,pectin,chitin,and chitosan)have been studied.It was confirmed that crystallites are inaccessible for water,and therefore water molecules can interact only with polar groups in noncrystalline(amorphous)domains of biopolymers.The isotherms of water vapor sorption for various polysaccharides had sigmoid shapes,which can be explained by the absorption of water molecules in heterogeneous amorphous domains having clusters with different packing densities.The method of contributions of polar groups to sorption of water molecules was used,which allowed to derivate a simple calculating equation to describe the shape of sorption isotherms.The wetting of biopolymers with water was accompanied by a high exothermic thermal effect,in direct proportion to the amorphicity degree.The sorption values and wetting enthalpies of amorphous domains of biopolymers were calculated,which allowed to find the hydrophilicity index and compare the hydrophilicity of the various polysaccharides.

气态水补给条件下不同类型土水分迁移规律及冻胀特性研究

使用自主研发的水分迁移和冻胀试验设备,对比分析砂土、粉质黏土、人工制备75%砂土+25%粉质黏土、25%砂土+75%粉质黏土在水汽补给条件下水分迁移规律及冻胀特性,研究了不同类型土试样冻结时间与含水率、温度场、冻胀量、冻胀力之间的变化规律,建立了不同类型土试样冻胀量和冻胀力的拟合公式。研究表明:土性对水分迁移影响较为显著,冻结7 d后,砂土试样峰值含水率达到22.1%;75%砂土+25%粉质黏土试样峰值含水率为17.1%,25%砂土+75%粉质黏土试样峰值含水率为10.1%,粉质黏土峰值含水率变化幅度不大。随着土中细粒含量的增加,试样温度场达到稳定所需的时间越长,冻结7d后不同类型土试样温度场均趋于基本稳定。冻结7 d后,不同类型土冻胀量和冻胀力差别较大,砂土试样冻胀量达到0.71 mm,75%砂土+25%粉质黏土试样冻胀量为0.55 mm,25%砂土+75%粉质黏土试样冻胀量为0.36 mm,粉质黏土试样冻胀量变化不大;不同类型土冻胀力随冻结时间的增加呈正相关线性关系,相同高度处试样冻胀力随着土中细粒含量的增加有所减小。