国内外医用以及颗粒物防护口罩标准对比

文章系统介绍并对比了国内外医用防护口罩和颗粒物防护口罩标准及其技术指标,分析了过滤效率、密合性、呼吸阻力等核心指标技术要求的特点和差异,以及不同技术指标对口罩防护效果和适用场景的影响。在此基础上,对不同类型的口罩进行防护等级分类,并提出合理的选用建议,为促进防护口罩的规范化研发、生产和销售提供理论指导。     

新型冠状病毒防护口罩过滤效率测试标准比对

为解决新冠疫情期间不同国家符合不同标准的防护口罩进入我国市场,造成公众对口罩过滤效率相关概念认识不科学、不全面的问题,系统介绍与比较了国内外认可度较高的GB 2626—2019、GB 19083—2010、美国42 CFR 84第K部分、EN 149:2001+A1:2009、EN 13274—7:2019等标准中过滤...     

口罩过滤效率检测标准的分析

分析了国内外口罩过滤效率的相关标准,论述了标准中规定的具体技术要求与检测方法,以及口罩过滤效率检测介质的选取具体要求,并对其进行了评述,以利于完善健全我国各行业的口罩标准,规范我国口罩市场,保障口罩使用者健康和生活品质。     

口罩用抗菌空气过滤材料的研究进展

口罩用抗菌空气过滤材料不仅能够对颗粒物与细菌等进行过滤、截留,而且能够杀灭细菌或抑制细菌活性,大幅提高口罩对呼吸道细菌传染病的防护性能。概述了近年来金属类抗菌剂、有机类抗菌剂、光催化类抗菌剂及金属有机骨架(MOF)类抗菌剂在口罩用抗菌空气过滤材料中的应用进展,从过滤性能、抗菌性能及应用性等角度系统分析了当前口罩用抗菌空气过滤材料的发展现状和存在的问题,并对其发展前景进行了展望。     

防护口罩测试标准的分析与思考

对比分析国内外防护口罩的测试标准及这些标准在过滤效率测试方面的异同点,着重讨论3个国内标准中测试项目制定的发展趋势及其不足之处,并提出国内相关标准今后制修订时需考量的因素,以利于进一步完善国内防护口罩标准体系,规范国内防护口罩市场。     

自吸过滤式口罩的相关标准及存在的差异

介绍了关于自吸过滤式口罩的两套国家标准,论述了标准中规定的具体内容,指出两套标准在口罩的阻尘效率测试方法和试验粉尘的选取中存在的差异,并对差异进行了分析讨论,从而得出以下结论:测试方法和试验物质也要实现标准化,这样结果才具有可比性,以便用于规范市场。     

滤纸微纳结构对品质因子的影响

本研究制备了以亚微米级玻璃棉为主体的微纳结构滤纸,探究了不同粒径过滤颗粒对滤纸过滤性能的影响.结果表明,粗纤维(平均直径0.69μm)滤纸在特定粒径过滤颗粒下表现出优于细纤维(平均直径0.24 μm)滤纸的过滤性能.当过滤颗粒粒径≤100 nm时,粗纤维滤纸对80nm和100 nm颗粒过滤的品质因子最大,过滤性能更好;...     

丙烯酸酯皮革填充乳液的粒径及其分布

采用不同的聚合方式和预乳化工艺 ,合成了丙烯酸酯皮革填充乳液。系统研究了聚合方式、复合乳化剂的用量和配比、聚合温度、官能团单体含量和搅拌强度对丙烯酸酯共聚物乳液粒径及其分布的影响     

非织造布孔径分布及过滤效率研究

非织造布是一类具有三维网络结构的多微孔材料,微孔结构形态是非织造布的一项重要性能指标,与过滤效率密切相关。测试了水刺非织造布的孔径、孔径分布以及过滤效率和阻力,研究了不同气体流量和不同试样层数(厚度)时试样的过滤效率和阻力的变化趋势。结果表明:非织造布可以过滤粒径比其孔径小很多的颗粒,过滤性能优良;在增加非织造布层数时,可以通过降低流量的方法达到既提高过滤效率,又降低过滤阻力的目的;在非织造布层数相同的条件下,采用更小直径的纤维制造非织造布,可以在不增加阻力的情况下大大提高过滤效率。     

Particle size distribution of break,sizing and middling wheat flours by laser diffraction

The particle size distributions of wheat flours collected along a milling diagram were assessed. Nine wheat varieties from the genetic trait Triticum aesticum vulgare and differing in hardness were studied for two consecutive years. Break, sizing and middling flours were collected for each wheat at different stages in an experimental mill, with all the milling conditions being kept constant. The particle size distributions were measured from 1·5 to 600 μm by using a laser light diffraction apparatus. The distributions were compared by principal component analysis. The method provided a global and synthetic comparison of all the flour fractions. In the case of the soft varieties, the distributions exhibited a first mode around 25 μm, corresponding mainly to isolated starch granules. The distribution of this mode was very low or non-existent for the hard varieties. As the milling conditions were the same for all the wheats, the different proportions measured for this mode were interpreted as being directly representative of the wheat hardness. The proportion of the 25 μm mode was considered as a measure of the ability of the wheat to release starch granules and could be used to follow a grinding or milling process. © 1998 Society of Chemical Industry     

Effect of different dietary geometric mean particle length and particle size distribution of oat silage on feeding behavior and productive performance of dairy cattle

Twenty lactating Holstein cows (5 primiparous and 15 multiparous) were used in a 5 x 5 Latin Square design, with 5 treatments and 3 periods of 21 d each. Diets contained 25% corn silage, 25% oat silage, and 50% concentrate (dry matter basis). The 5 treatments tested in the experiment were long oat silage (LOS), medium oat silage (MOS), fine from long oat silage (FLOS), fine from medium oat silage (FMOS), and half LOS plus half FLOS (LFLOS). The geometric mean particle length (GMPL) of the diets was 6.68, 5.19, 4.46, 4.35, and 5.39 mm for LOS, MOS, FLOS, FMOS, and LFLOS, respectively. The LFLOS was designed to provide dietary GMPL similar to MOS, but with a more bimodal particle size distribution (PSD). Linear and quadratic effects of GMPL were tested, based on the mean GMPL of the feed actually consumed (cGMPL). Contrasts were used to test for the effect of different PSD (MOS vs. LFLOS) and to test for differences between FMOS and FLOS, which would indicate unequal fermentations in the MOS and LOS silos. No differences were detected between FMOS and FLOS in most of the variables measured. Increasing cGMPL linearly decreased dry matter intake, milk production, and milk protein percentage and yield without affecting milk fat percentage, milk fat yield, ruminal pH, and ruminal volatile fatty acid concentration. Although cows fed diets with increasing cGMPL spent more time eating and chewing per day and per kilogram of dry matter intake, there was no effect of cGMPL on rumen pH. Feeding medium oat silage increased milk fat percentage and yield compared with feeding a mixture of long and fine oat silage.     

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.