The effect of moisture and air gap on the thermal protective performance of fabric assemblies used by wildland firefighters

The thermal protection performance (TPP) provided by fabric assemblies used by wildland firefighters is greatly affected by both the moisture and the air gap trapped in multilayer fabrics. In this paper, the effect of moisture, coupled with air gap on TPP was analyzed under radiant heat exposures of 21 kW/m². The air gap sizes from 0 to 5.2 mm were analyzed using an air gap height regulation device; the moisture content of the multilayer fabric combinations around 0–70% were obtained by spraying distilled water to simulate varying amounts of sweat absorption. The results obtained indicate that certain air gaps entrapped in multilayer fabric system have a positive effect on TPP for both dry and wet multilayer fabric combinations. However, obvious trend changes in thermal protection were observed among dry and wet configurations when the air gap was moved to different positions. For the wet configurations, the second-degree burn time increased as the air gap moved further from the heat source, which was contrary to burn time response under dry conditions. These findings suggest that the complicated reciprocal effect of air gap and moisture on thermal protection should be both considered in analyzing the TPP of fabric assemblies.     

Study on thermal and evaporative resistances of multilayered fabric ensembles

The present work deals with the study on thermal and evaporative resistance of multilayered fabric ensembles meant for cold weather applications. Three-layered structure is used to study the thermal comfort properties. Knitted fabric and polytetrafluoroethylene coated fabrics were used in inner and outer layer, respectively. Needle punched fabrics produced from polyester fibre were used in middle layer. Fifteen different non-woven fabrics were produced according to Box and Behnken experimental design for three variables and three levels by varying mass per unit area, punch density and depth of needle penetration. The produced fabrics were evaluated for thermal and evaporative resistances with and without inner and outer layer fabrics. Thickness, air permeability, bulk density and porosity of the needle punched fabrics were studied. The properties of the fabrics were analyzed for statistical significance by using ‘Design-Expert’ statistical software. Artificial neural network model was developed to predict the properties of fabrics and validation of model was done with the testing data-set. The performance of prediction was evaluated by mean square error, mean absolute error percentage and correlation coefficient. It was concluded that the predicted properties of fabric correlated well with the experimental results.     

Study on thermal resistance of multilayered fabrics under different compressional loads

In this work, the thermal resistance of multilayered fabric ensembles meant for cold weather conditions were studied under different compressional loads. An instrument has been developed to study the thermal resistance of fabrics under different compressional loads. The instrument consists of a test plate, guard plates and a bottom plate. The test plate and guard plates were assembled together as a single entity, which can be moved up and down with a screw shaft. A load cell was connected to the plate assembly to apply the required compressional load on the fabric specimen. Thermal resistance of multilayered fabrics was studied in the developed instrument under different loading conditions. Single-jersey knitted fabric, needle punched fabric and polytetraflouroethylene (PTFE) coated fabrics were used in the inner, middle and outer layer, respectively. Twenty different multilayered fabric ensembles with the same inner and outer layers were studied. The middle layers, i.e. needle punched nonwoven fabrics, were produced from polyester hollow fibres, with varying linear density of fibre, mass per unit area and punch density. The thermal resistance of multilayered fabrics obtained from the developed instrument was compared with the thermal resistance of instruments, namely sweating guarded hot plate (SGHP) and Alambeta. Regression equations were developed and the contour plots were drawn to analyse the effect of the fibre, fabric and process parameters. ANOVAs were conducted to find the significance of the compressional load, linear density of fibre, mass per unit area and punch density on the thermal resistance of fabrics. It was found that the thermal resistance obtained from the instrument follows the same trend as that of thermal resistance obtained from SGHP and Alambeta. Mass per unit area was found to have significant effect on the thermal resistance of multilayered fabrics under different compressional loads. The effect of punch density decreases with the increase in compressional load on the thermal resistance of multilayered fabrics. The thermal conductivity of multilayered fabrics was observed to increase with the increase in the compressional load.     

考虑内部辐射下织物热湿传递现象的数值研究

人体在着装情况下的热湿传递现象对人体的热舒适性的研究有着很重要的地位。考虑了由于温度差而引起的织物内部的辐射热传递，对织物中的热湿传递现象进行了数值研究，建立了考虑辐射现象下织物内部热湿传递的简单模型，并讨论了计算结果。     

消防服衣下空气层热传递机制研究进展

空气层热传递机制的研究不仅可为更加准确的实验室热防护性能测试提供指导,也可提高消防服热湿传递数值模拟的精确度。在阐述了热防护性能测试中空气层的作用以及空气层热传递模型的研究现状的基础上,分析了服装与人体之间空气层微气候的特征,从热传导、对流换热和辐射换热3个方面总结了空气层的热传递机理,提出不同条件下空气层传热模型建立的基本思路,并对未来消防服衣下空气层热传递机理的研究动向作出了预测。     

衣下空气层对透气型防护服热阻和湿阻的影响

为确定适宜的服装宽松量,提升透气型核生化(NBC)防护服的热湿舒适性,设计了穿着实验。在温、湿度可控制的气候室内,借助出汗暖体假人和三维扫描技术,观察常温、静止状态下5套不同松量服装的热湿传递性能,探讨衣下空气层对NBC防护服热阻和湿阻的影响。研究结果表明:衣下空气层体积与平均厚度的增量变化相似,不同松量服装的衣下空气层对服装总热阻和总湿阻有显著影响;随着透气型NBC防护服松量的增大,服装总热阻随着衣下空气层的增加呈现先增后减的变化趋势,服装总湿阻随着衣下空气层的增加呈现逐渐增大的变化趋势。     

含水率对消防服用多层织物系统热蓄积的影响

为全面准确地评估湿态下消防服用多层织物系统的热防护性能,通过改进现有的热防护性能测试仪器,采用传统热防护性能实验与蓄积热实验2种方法,利用模拟人体皮肤传感器取代标准测试中的铜片热流传感器,基于Pennes热量传递方程,根据Henriques人体皮肤烧伤模型做出烧伤预测,并利用迭代法获得二度烧伤最少热暴露时间。分析了织物系统含水率对二度烧伤最少热暴露时间及热蓄积指数的影响。实验结果表明:2种实验方法测得的二度烧伤最少热暴露时间随含水率的增大明显降低,热蓄积指数也呈降低趋势;二度烧伤最少热暴露时间与含水率之间存在显著的线性负相关关系。     

消防员防护服面料的热湿舒适性

为研究消防员防护服面料的舒适性并考察其是否满足欧美国家相关标准,选取了我国消防员防护服常用的几种面料,进行单层织物热阻和湿阻以及多层织物热阻、湿阻和总热损失的测试与分析,考察空气层对多层织物热阻的影响,并将测试结果与欧美标准的相关要求进行对比。结果表明:在厚度大致相同时,外层面料的密度对热阻和湿阻影响较大;因为隔热层材料是非织造布结构,热阻和湿阻较大;空气层的位置对多层织物的热阻值影响不大,但其厚度对多层织物的热阻影响较大;选取的几种面料组合,湿阻低于30 Pa·m~2/W,总热损失高于205 W/m~2,均满足欧美国家相关标准要求。     

应用ABAQUS的织物热传递有限元分析

为拓展机织物热舒适性设计、评估和优化的思路,提供一种有效预测织物热阻的方法,基于织物的三维模型及传热学理论,对织物系统进行一维热传递的数值模拟,得到织物传热过程中的温度分布特征。利用显微图像及切片技术获取织物几何结构参数,建立平纹织物的几何模型,并与纱线周围静止空气装配,构成织物系统的三维模型,借助有限元分析软件ABAQUS,根据模拟环境设置边界条件与相互作用,计算模型的数值解。最后通过模拟皮肤散热的恒温平板实验,对数值模拟结果进行验证,结果显示：织物外表面温度的模拟值与实验值随时间变化的一致性较好,理论热阻值与实验热阻值相对误差为3.9％,二者吻合度较高。     

手臂活动角度对服装局部热阻的影响

为研究手臂活动角度对衣下间隙局部分布及服装局部散热性能的影响,利用三维扫描仪量化了出汗暖体假人在6种手臂姿势下,12个体段的衣下间隙体积及接触面积,提取了表征人体活动空间大小的物理指标,测量了服装各体段的局部热阻。结果表明:手臂的前伸角度与衣下间隙体积呈负相关性,而与接触面积呈显著正相关性,人体的活动空间随着手臂前伸角度的增加而显著减少;各体段的局部有效热阻呈现出非均匀的分布状态,局部衣下空气层体积越大、接触面积越小的体段,其有效热阻越大。服装的有效热阻可用衣下间隙体积与接触面积百分比共同预测。     

消防服用外层织物的热防护性能研究

对消防服外层织物用间位芳纶Nomex和New Star的织物、芳砜纶Tanlon织物、阻燃棉织物及聚苯并咪唑(PBI)纤维与对位芳纶Kevlar混纺织物的热防护性能进行了比较研究。实验结果显示Nomex织物具有较高的热防护性能(TPP),Tanlon及间位芳纶New Star织物热防护性能接近Nomex织物,三者无显著差异。热防护性能较差的阻燃棉织物在TPP实验中的质量损失率大。上述各类织物的热防护性能随着其面密度及厚度的增加而提高。     

消防服衣下空气层的作用与测定方法研究进展

为探究消防服衣下空气层对消防服热防护性能的影响,从衣下空气层的厚度与位置、影响因素以及测量方法 3个方面综述了消防服衣下空气层研究的发展过程及最新进展,分析了现有研究中存在的问题。研究表明:衣下空气层的厚度和位置影响衣下热传递机制,从而影响消防服的热防护性能;织物的硬挺度和悬垂性、服装的合体度以及人体动作影响消防服衣下空气层的分布;目前主要使用三维人体扫描技术获取燃烧假人裸体及着装状态下的三维图像,使用图像处理软件计算衣下空气层厚度。基于当前消防服衣下空气层的研究现状认为,未来研究需深入分析衣下空气层的作用机制,建立多层消防服衣下空气层的测量方法,提高衣下空气层的测量精度。     

玉石纤维热湿舒适性能研究

探究了玉石纤维的保暖性、透湿性,以及空气层厚度变化对其保暖性能的影响。选用热阻为保暖性的指标,蒸发散热效能为透湿性指标,对玉石纤维织物在干燥状态和汗湿状态下的热阻和蒸发散热效能进行测试,并与相近规格的涤纶、莫代尔、涤棉、棉＋超细丙纶织物进行了对比。测试结果显示,5种织物中玉石纤维织物的热阻值最小,蒸发散热效能最大,就不同空气层厚度对玉石纤维在干燥状态和汗湿状态下的热阻影响进行测试,得出热阻值随着空气层厚度的增加先增大后减小,空气层厚度为15mm时热阻达到最高值。     

Investigating the effect of material and weave design on comfort properties of bilayer-woven fabrics

The paper focuses on the development of a bilayer-woven fabric and investigating the effect of weave design and material type on its comfort properties. Face layer was plain woven with cotton yarn, while two different weave designs (2/2 and 3/1 twill) and four different materials (cotton, polyester, micropolyester and nylon) were used for the back layer. The comfort properties of fabric, including air permeability (AP), thermal resistance, water vapour resistance and overall moisture management capacity, were determined. It was found that both the layers of fabric as a whole contribute to the comfort properties of bilayer fabric. The highest AP was exhibited by fabrics having both layers of cotton, while 3/1 twill samples have a lower value of thermal resistance as compared to the 2/2 twill samples. The results further showed that micro polyester woven in 3/1 twill weave exhibits better comfort properties.     

发热纤维保暖针织面料的工艺及热舒适性研究

介绍了发热纤维的特点及性能,制定了发热纤维针织保暖面料的开发工艺,其中包括设备参数、原料、织针排列、三角排列、穿纱方式、线圈长度、面料参数等;并对有关针织保暖面料的热舒适性能,如透气性、保温性及透湿性等进行测试,从而为保暖面料的生产与开发提供了理论依据。     

聚苯硫醚织物的制备及热学性能研究

通过制备相同经纬密度不同织物组织的样布,对聚苯硫醚机织物的耐热性能、热稳定性能以及导热性能进行测试分析.根据实验数据可知,聚苯硫醚织物具有良好的耐热性能和热稳定性能,以及极佳的热防护性能;1/2斜纹相比于平纹和其他三种斜纹织物组织是更适合于防护服外层面料的组织.     

不同养殖模式下清远麻鸡的组织学评价标准研究

目的研究不同养殖模式下清远麻鸡的组织学评价标准。方法测定不同养殖模式下清远麻鸡肌肉的肌节长度、肌纤维直径、肌纤维密度、肌纤维面积比例、结缔组织面积比例和脂肪面积比例。结果不同养殖模式出产的清远麻鸡组织学性状差别较大,农户散养模式出产的清远麻鸡肌节最长、肌纤维直径最粗、肌纤维面积比最大,走地鸡养殖模式次之,笼养模式出产的清远麻鸡肌纤维直径最小、密度最大、结缔组织面积比和脂肪组织面积比最大。结论依据组织学特性对清远麻鸡的鸡肉品质进行了分级,初步制定了清远麻鸡组织学分级评价标准。     

形变状态下热防护织物的蓄放热双重特性

为了探究形变状态下热防护织物的防护机制,研发了形变状态下织物蓄放热特性测试仪,在此基础上对拉伸形变状态下6种热防护织物的蓄热防护性能和放热危害性能进行量化研究。结果表明:随着织物拉伸率的增加,织物在热暴露阶段的累计蓄热量降低,而皮肤得热显著提升,织物的热防护性能下降;当双层织物系统发生拉伸形变时,外层织物较其隔热层通常蓄积更多的热量,织物系统累计蓄热量的降低主要源于隔热层蓄热量下降;在冷却阶段,织物释放至皮肤的累计蓄热回放量随着其拉伸率的增加而逐渐降低,织物的蓄热回放效率逐渐增大。织物发生拉伸形变时,其累计蓄热回放量与累计蓄热量呈正比。     

几种不同组织结构的衬衫面料保形性研究

根据常见的衬衫面料组织结构,使用JC9.7 tex纱线设计了6种不同组织结构的面料,研究不同组织结构对织物保形性的影响。对面料的保形性(尺寸稳定性、抗折皱性、外观平整度、抗起毛起球性、顶破性、悬垂性)及舒适性(透气、透湿性)进行了测试。结果表明:组织结构对织物的折皱回复角、外观平整度等级、顶破强力、透湿量与透气率有直接影响;织物紧度太大、太小都不利于织物的折皱回复,相同紧度下斜纹组织的抗皱性比平纹好;6种组织结构中2/2斜纹组织抗折皱性最好,2/2方平组织的顶破强力、抗起毛起球等级最高,2/2破斜纹透气、透湿性最好,2/2斜纹组织具有良好的保形性。     

笃斯越桔花青素在不同pH条件下热稳定性的研究

研究分析了笃斯越桔花青素提取物(BBAE)在不同pH条件下热稳定性的变化,测量指标包括吸光值、颜色及其ABTS自由基清除能力。研究结果表明:在pH4～6加热时,BBAE的吸光值无明显变化,提示其在酸性条件下有较好的稳定性。在pH7和pH8加热时,尤其在pH7时,BBAE的吸光值明显降低,表明BBAE在pH7条件下的热稳定性最差。通过色差仪测定BBAE溶液的L*、a*、b*值从而算出H(色调)值。随着加热温度的升高,pH为4～8时的BBAE溶液的H值呈现不同程度的升高,且逐渐趋近于90°。这表明在加热过程中,BBAE溶液的颜色由最初的红色逐渐向黄色转变。pH为7时的BBAE溶液在吸光值降低,颜色变黄的同时,其ABTS自由基清除率也有显著性的下降。