关于提高称重法水蒸气透过率测试设备测试性能的分析

称重法是进行材料水蒸气透过率的基础测试方法,也是历史最悠久、应用最广泛的一种测试方法。称重法所包含的几种测试方法(例如增重法、减重法等)最初都需要人工操作来完成测试,相关仪器的自     

水蒸气透过量测定仪比对试验分析

目的一探讨我中心两台不同水蒸气透过量测定仪测定结果之间的可比性。方法一重复性试验用标准膜分别在两台仪器连续检测10次,比对试验是对同一批样品先后在两台仪器上进行水蒸气透过量测定,通过T检验、u检验进行判断。结果一试验仪器重复性试验差异不显著（P〉0．05）,比对试验结果差异显著（P〈0．05）。结论一在使用两台或两台不同型号水蒸气透过量测定仪时,对仪器进行校准、保养及维护,应同时建立比对制度。比对试验建议采用同一条件下,使用相同品种、规格、型号、精度或分辨力的仪器作比对实验;对于不同型号、不同测定原理、不同精度的仪器不予以采用;以达到检测结果的一致性。     

镀铝薄膜水蒸气透过性试验分析

简述了不同相对湿度下镀铝薄膜的水蒸气透过性测试结果的差异,分析其原因。     

红外传感器法设备改进对透湿性测试的影响

目的探究改进后的红外传感器法设备对包装材料透湿性测试的影响及应用性能的提升效果。方法改进设备控温技术及夹样装置,保证试验过程温度稳定,可同时测试薄膜/片材、容器类试样,以基础方法——杯式法设备测试为参考,并分别采用改进前后的红外传感器法设备依次测试1.2 mm皮革、25μm PET薄膜、230μm太阳能背板片材、20μm PP薄膜、100μm PET/AI/PA/CPP与12μm VMPET薄膜这6种不同级别透湿性材料,分别在温度为23℃、相对湿度为90%与温度为38℃、相对湿度为90%这2种试验条件下的水蒸气透过率。结果改进后红外传感器法与杯式法设备在试验时引入的相对不确定度基本相同,与改进前设备相比,改进后红外传感器法设备的不确定度、与杯式法测试值间的相对偏差,以及各组数据间相对偏差与相对标准偏差均得到了降低。结论改进后红外传感器法设备测试不同性能包装材料水蒸气透过率的可靠性、准确性、重复性、稳定性均有提高。     

《塑料薄膜和薄片水蒸汽透过率的测定——电解传感器法》标准介绍

本文介绍了GB/T 21529-2008<塑料薄膜和薄片水蒸汽透过率的测定电解传感器法>的实施进度.并且将该标准与ISO 15106-3:2003、GB/T 1057-1988进行了详细的条款对比.     

辐照对食品接触材料的水蒸气透过量的影响

主要研究了不同剂量的辐照处理（5kgy～50kgy）对食品接触材料PE膜、CPP膜水蒸气透过量的影响。试验结果表明PE膜经0～50 kgy剂量辐照处理后,与未辐照的相比其水蒸气透过量变小,其水蒸气阻隔性有所提高。CPP膜经0～40kgy剂量辐照处理后,与未辐照的相比其水蒸气透过量呈上升趋势,其水蒸气阻隔性呈下降的趋势。     

材料透湿性测试方法介绍——传感器法

20世纪70年代，传感器法开始应用在透湿性测试领域中，在此之前使用的都是称重法，通过30多年的发展，它已成为一种重要的测试方法，应用范围十分广泛。通常的透湿性测试传感器法主要有：红外线检定法、动态相对湿度测定法和电解分析法三种。     

GB／T 21529-2008《塑料薄膜和薄片水蒸汽透过率的测定——电解传感器法》标准介绍

本文介绍了GB／T 21529—2008《塑料薄膜和薄片水蒸汽透过率的测定电解传感器法》的实施进度。并且将该标准与ISO 15106-3：2003、GB／T 1037-1988进行了详细的条款对比。     

水蒸气在高分子膜中的透过行为与气体膜法脱湿

在气体膜分离中,水蒸气的分离过程比其它非凝聚性气体更复杂,因为水分子可以通过氢键和聚合物链节中极性基团发生作用,使聚合物被溶胀、塑化;水分子自身可通过分子间氢键聚集成簇,这些因素导致了水分子在膜中的透过行为不再符合其它气体的透过规律.水蒸气在极性高分子膜中较高的渗透能力会在膜的下游侧产生浓差极化现象,消除浓差极化现象才能使水蒸气透过正常进行.膜材料的选择要权衡亲水性和疏水性,共混和嵌段共聚是解决这一矛盾的有效手段.水蒸气在高分子膜中的较高透过能力使其用于气体膜法脱湿成为可能.现以压缩空气膜法脱湿为例,介绍了影响膜法脱湿效率的主要因素,也介绍了气体膜法脱湿的其它应用领域.     

透湿性测试称重法的现状分析以及发展趋势

透湿性测试方法称重法在测试准确性、测试重复性等方面都受到争议,称重法的可发展性以及是否会被新方法所取代也逐渐成为关注的焦点.文章系统地分析了称重法的测试原理、使用现状,并介绍了其未来的发展趋势.     

Permeation and Sorption of Water and Gases Through EVA Copolymers Films

The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and sorption measurements. In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA, there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady increase in the water permeability in the EVA copolymers. In the case of gas permeation, both for O₂ and CO₂ and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient. This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients especially for oxygen. In the EVA rubbery copolymers, The O₂ solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO₂ one increases due to the overall interactions between CO₂ induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H₂O/CO₂ and H₂O/O₂ selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good candidates for applications using high perm-selectivity properties. Electronic Publication     

水蒸汽在软包装薄膜中的传递行为

在不同温度和相对湿度(RH)条件下,对代表不同亲水性能的三种常见软包装膜——聚乙烯(PE)膜、聚乙烯醇(PVA)膜、大豆分离蛋白(SPI)膜的水蒸汽透过率(WVTR)进行了一系列测定,并在此基础上计算了其水蒸汽透过系数(WVP)。实验结果表明,随温度升高,三种膜的WVTR均呈指数上升趋势。湿度对三种膜WVTR的影响表现出一定差异,对PVA膜和SPI膜,其WVTR与RH之间满足指数方程y=A*exp(x/B)+C,而PE膜的WVTR与RH间表现为线性关系。PVA膜和SPI膜的WVP受湿度影响大于温度对其影响,相反,PE膜的WVP受温度影响程度显著于环境湿度。     

The Effect of Thermal Reduction on the Water Vapor Permeation in Graphene Oxide Membranes

In the present study, the influence of the thermal reduction on the water vapor transmission properties of thin graphene oxide (GO) membranes is evaluated. The macroscopically measured property of the Water Vapor Transmission Rate (WVTR) exhibits step like dependence contrary to the gradual microscopic structural alterations identified by several techniques (XPS, FTIR and XRD) applied in situ during the thermal annealing process. Three distinct regions of WVTR‐values associated with distinct interlayer distances i.e., >7.5 Å, ∼6 Å and <6 Å are essentially observed which may be compared to the findings of the recently reported first principle calculations. Our experimental results enable the understanding of the water vapor unimpeded transmission through the layers of the oxygen rich GO nanostructured membranes and consequently facilitate the design of functional membranes for separation applications.     

Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings

The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6AI-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of 02, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O% and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(AI,Cr)2O4,NiO and AI2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed     

提高谷类可食性薄膜水汽阻隔性的有效途径

水汽阻隔性是谷类可食性薄膜重要特性之一,它直接影响到被包装食品在保存期内质量的变化。本文仅就提高谷类可食性薄膜水汽阻隔性的有效途径进行了一些研究。     

Evaluation of Permeability Through Permeation Experiments: Isostatic and Quasi-isostatic Methods Compared

Isostatic and quasi-isostatic permeation experiments were used to characterize the permeability of 1-hexanol through polypropylene films. The quasi- isostatic method was considered as an isostatic experiment at the limit a of null purging stream flow rate. Permeability values obtained through the isostatic method showed dependency on the purging stream flow rate. The extrapolated value at zero purging stream flow rate is in agreement with the data obtained via the quasi-isostatic procedure. Diffusion coefficient values were also determined. The isostatically obtained diffusion coefficients behave similarly to P. However, the value at zero flow rate differs significantly from the value obtained through the quasi-isostatic method. From these results the validity of permeation experiments for the evaluation of the diffusion coefficient is questioned.     

水雾的红外衰减性能实验与分析

烟幕干扰光电设施的效果与其组成成分密切相关.以NaCl为填料,从水雾的光学和微物理特性角度,分析微粒消光特性的主要影响因素,通过实验比较不同浓度、不同用量和不同靶温条件下NaCl水雾对中远红外辐射的衰减性能,实验表明增大NaCl溶液的浓度和用量有利于提高水雾的消光能力,NaCl水雾对高温目标的近红外辐射衰减能力更强些.应用米式理论,对粒径服从对数正态分布的水雾在红外传输窗口的消光性能进行了计算和分析,波长分别为3.5μm和10.591μm时,其透过率分别为38%和55%,提出选用具备良好电磁特性和悬浮性能的干扰填料是增强水雾干扰性能的有效途径.     

Water Vapor Adsorption Properties of Amorphous Cefditoren Pivoxil Evaluated by Adsorption Isotherms and Microcalorimetry

Water vapor adsorption of ground cefditoren pivoxil was studied. The amount of water adsorbed increased with a decrease in the crystallinity of cefditoren pivoxil. It was found from the microcalorimetric measurements that the differential heat of water vapor adsorption at 1.5% adsorbed water increased with decreasing crystallinity of cefditoren pivoxil, suggesting that hygroscopicity of cefditoren pivoxil was enhanced by grinding. These results indicated that hydrophilic adsorption sites in cefditoren pivoxil increased through the grinding process. The results of infrared (IR) spectra examination suggested that the increment of hydrophilic adsorption sites through the grinding process resulted from the change of the environment of the carbonyl groups in two esters and amide.     

膨体聚四氟乙烯微孔薄膜的透湿性

采用干燥剂法系统测试了ePTFE微孔薄膜的透湿情况,分析了透湿性影响因素,得出以下结论:在实验范围内,ePTFE薄膜的孔隙率、孔径和厚度等结构参数对透湿速率影响较小,透湿的主要影响因素是环境温度和湿度。在相同的湿度下,环境温度对透湿量和透过系数的影响显著,并随温度提高急剧增加;在相同温度下,透湿量随湿度的增加而增加,而透过系数变化不大。     

水蒸汽压缩式制冷机性能研究

水作为一种完全环保、非常廉价的天然制冷剂,在过去十多年里受到了世界范围的关注和研究。根据最近公开发表的有关水蒸汽压缩机(WVC)的研究结果,对以水为制冷剂的蒸汽压缩制冷机进行了理论分析和研究。在其它部件性能一定的条件下,对于不同的蒸发温度(7℃、10℃)和冷凝温度(35～40℃),分别将水蒸汽当作理想气体和实际气体,对分别采用等熵压缩过程、饱和多变压缩过程的两种水蒸汽压缩制冷机的性能(功耗和COP)进行了计算和对比。结果显示,采用不同压缩过程的水蒸汽压缩机的耗功有明显差别;水蒸汽压缩制冷机的COP值可达9．0以上,该类制冷机是CFC和HCFC类制冷机很有前途的替代型制冷机。