PP/SiO2和PET/SiO2复合气凝胶的制备及性能研究

为改善传统SiO2气凝胶脆性较大和易碎等缺陷,选取聚丙烯(PP)针刺非织造布和涤纶(PET)吸声棉非织造布作为增强体,以正硅酸乙酯(TEOS)为硅源,采用酸碱两步法和溶胶-凝胶法,以三甲基氯硅烷(TMCS)为疏水改性剂,再通过常压干燥法制备PP/SiO2和PET/SiO2复合气凝胶.对SiO2复合气凝胶的微观形貌结构及亲疏水性能、力学性能、导热性能、吸声性能等进行表征和测试.结果表明:SiO2气凝胶以黏附或填充的方式附着于两种非织造布的纤维表面及孔隙中,且复合未改变非织造布中原料分子的晶型结构;所得PP/SiO2和PET/SiO2复合气凝胶具有良好的弯曲性和韧性,疏水性提高,导热系数更低,吸声系数提高.     

SiO_2气凝胶在非织造布加工中的应用

SiO2气凝胶是一种新型低密度纳米无机材料,具有比表面积大、导热率低等优良性能,已在电力、化工、建材等领域得到广泛的应用。通过涂层和浸轧的方法将纳米SiO2气凝胶应用于聚酯非织造布加工中,探讨纳米SiO2气凝胶对其力学、热学等相关性能的影响。实验表明,采用涂层或浸轧方式将SiO2气凝胶施加于聚酯非织造布上,无益于隔热效果的改善,但可以改善非织造布的机械性能,并具有一定的阻燃效果。     

TiO2/SiO2气凝胶隔热涂层帐篷材料的制备

试验选取TiO2和SiO2气凝胶,制备SiO2气凝胶涂层剂、TiO2涂层剂以及TiO2/SiO2气凝胶涂层剂,并将其涂覆在帐篷表面,制得隔热帐篷材料。通过测量涂层织物的内外温差、拉伸断裂强力和导热系数,讨论功能粒子质量分数对隔热效果的影响。结果表明,未涂层织物内外温差为19.8℃;当SiO2气凝胶质量分数为5%时,织物内外温差为7.9℃;当TiO2质量分数为12%时,织物内外温差为2.6℃;当两者复配以后,5%SiO2气凝胶+12%TiO2时,帐篷隔热性能最好,和未涂层织物相比,内外温差降低17.2℃,拉伸断裂强力为2 173.3 N,导热系数为0.056 W/(m·K)。     

疏水纳米纤维素气凝胶的制备及保温隔热性能

针对废旧纯棉织物再利用率较低的问题,以废旧纯棉织物为原料制备纳米纤维素气凝胶,并分别采用甲基三甲氧基硅烷(MTMS)和三甲基氯硅烷(TMCS)为改性剂对气凝胶进行疏水改性。采用扫描电子显微镜、红外光谱仪、热重分析仪、表面接触角测试仪以及导热系数测试仪研究了疏水改性剂种类和添加量对气凝胶结构和性能的影响。结果显示,采用MTMS为改性剂制备的疏水纳米纤维素气凝胶的结构和性能优于TMCS。综合考虑MTMS添加量对气凝胶结构、疏水性、热稳定性和保温隔热性的影响,得出MTMS与CNF的最佳质量比为2∶1,此时疏水气凝胶的结构比较平整均匀,疏水性、热稳定性分别增加了1.22倍和1.43倍,导热系数降低了12.3%。     

冷冻干燥法制备淀粉气凝胶及其疏水改性研究

利用溶胶-凝胶-冷冻干燥技术制备了淀粉气凝胶材料，测试并分析了淀粉种类及直链/支链比例对气凝胶材料形貌、密度、收缩率、孔隙结构以及隔热性能的影响。优选出木薯淀粉为最适宜制备隔热气凝胶材料的原料，其所制备的气凝胶具备大孔、介孔及部分片层结构，密度低至0.094 g/cm³,孔隙率高达88.63%,导热系数低至0.043 W/(m·K),具有优良的保温隔热性能。通过一步法制备柠檬酸交联改性木薯淀粉气凝胶，以甲基三甲氧基和十六烷基三甲氧基硅烷包覆疏水纳米SiO₂制备疏水溶液，然后制备加入交联剂和自制硅烷疏水溶液的改性木薯淀粉气凝胶。扫描电镜测试结果表明，制备的改性气凝胶材料具有更加坚实的网络结构和致密的孔隙。导热系数测试结果表明，改性木薯淀粉气凝胶导热系数低至0.048 W/(m·K)。接触角测试结果表明，水滴滴入立即测量接触角达139.5°,5 min后测量接触角仍有129.5°,且表面和内部均有疏水效果。改性气凝胶具有优良的保温隔热以及疏水性能，其在食品保温材料领域具有广阔的应用前景。     

纳米SiO2气凝胶改性木材的研究

纳米无机质气凝胶对木材进行改性处理复合材是一种新方法。本文介绍了气凝胶的概念及特性,分析了纳米SiO2气凝胶改性木材的工艺、复合机理及其性能评价。     

几种新型的粮食控温技术

介绍应用反射性隔热材料、导热系数小的隔热材料、喷涂聚氨酯泡沫塑料以及利用隔热保温窗进行控温,并对其控温效果加以分析。     

硅烷偶联剂改性纳米纤维素气凝胶的制备及其表征

为研究硅烷偶联剂含量对纳米纤维素气凝胶性能的影响,选用氨丙基三乙氧基硅烷(KH-550)和甲基三甲氧基硅烷(MTMS)2种硅烷偶联剂对纳米纤维素(CNF)气凝胶进行修饰。通过扫描电子显微镜、热重分析仪、万能强力机和热常数分析仪进行测试与表征。结果表明:硅烷偶联剂的添加使改性气凝胶红外光谱图上出现了含硅峰值,但并未改变气凝胶的组分;改性后气凝胶的孔洞明显增多;MTMS与CNF的质量比为1∶2时,改性气凝胶的压缩回弹性最好(7.25 kPa);MTMS的添加使改性气凝胶具有良好的疏水性,接触角为156°;随着KH-550的添加,气凝胶导热系数先降低后升高;随着MTMS的添加,气凝胶导热系数逐渐降低。     

SiO_2气凝胶的制备及其在隔热涂层织物中的应用

以正硅酸乙酯(TEOS)为硅源,三甲基氯硅烷(TMCS)为改性剂,通过溶胶-凝胶法,采用常压干燥工艺制备疏水改性SiO_2气凝胶,并应用于隔热涂层织物的制备。研究TEOS、H_2O、EtOH物质的量比,pH,TEOS、TMCS物质的量比对气凝胶密度和导热系数的影响,优化工艺条件;采用SEM、全自动比表面积与孔径分析仪、水接触角测试仪表征其结构与性能,测试涂层织物的隔热性能,并与未改性SiO_2气凝胶涂层织物比较。结果表明,当TEOS、H_2O、EtOH物质的量比为1∶5∶8,pH为6,TEOS、TMCS物质的量比为1∶1时,疏水改性SiO_2气凝胶具有纳米级多孔网络结构,平均孔径为16.86 nm,孔隙率为96.90%,导热系数为0.027 4 W/(m·k),并具有良好的疏水性。经红外加热灯照射30 min后,涂层织物正反面温差可达4.4℃,比未改性SiO_2气凝胶涂层织物提高了3.6℃,具有较好的隔热性能。     

纤维素基气凝胶在保温隔热领域中的研究进展

纤维素具有储量丰富、来源广、可再生、可降解、易于化学改性等显著优势。纤维素基气凝胶具有优异的力学性能和热学性能,在建筑、航空航天、石油化工等领域受到了广泛关注,有望成为替代传统气凝胶的理想选择。随着科技的快速发展,纤维素基气凝胶作为保温隔热材料的性能不断被优化,应用不断被拓展。本文简要介绍了纤维素基气凝胶的制备方法,综述了纤维素基气凝胶作为保温隔热材料在航空航天、石油化工和建筑等领域的最新研究及应用进展,提出了制备和改性纤维素基气凝胶亟待解决的问题。     

热防护用气凝胶材料的研究进展

为了进一步强化气凝胶材料热防护性能在各个领域的应用,并且确定未来热防护用气凝胶材料的主要研究方向,本文首先简要介绍了气凝胶的定义、结构特点、性能以及隔热机制。其次对气凝胶材料的应用进行了阐述。然后将用于热防护的气凝胶根据原材料进行分类,并分别对各类气凝胶的研究现状展开论述。二氧化硅气凝胶研究时间最长且成果已经较为成熟,其他各类气凝胶的研究还有很大的进步空间,可以针对各类气凝胶材料所具备的独特的优缺点展开研究,以满足各方面的特种需求。最后提出了气凝胶材料的未来发展趋势应该集中在提高耐温上限,消除高温后材料的粉尘问题,改善其力学性能,满足隔热承重一体化防护的需求,提高作为防护服隔热材料时的防水透湿性,创新制作工艺降低成本等方面。     

Aerogels for thermal insulation in high-performance textiles

For many garment applications where protection is needed against hostile environments, part of the requirement is for insulation to shield the wearer from extremes of temperature. For an insulating garment to be fully effective, it needs to allow the wearer to move freely so that they can carry out their intended activity efficiently. Traditional materials achieve their insulation by trapping air within the structure thereby not only limiting heat loss by convection but also making good use of the low thermal conductivity of air to cocoon the wearer within a comfortable environment. To achieve effective protection with conventional textiles, it is usually necessary to have a thick fibrous layer, or series of layers, to trap a sufficient quantity of air to provide the required level of insulation. Several disadvantages arise as a result. For example, thick layers of insulating textile materials reduce the ability of the wearer to move in a normal manner so that the conduct of detailed manual tasks can become very difficult; the layers lose their insulating capacity when the trapped air is lost as they are compressed; the insulating capacity falls rapidly as moisture collects within the fibrous insulator – it does not have to become sensibly wet for this to happen; just 15% moisture regain can give a dramatic reduction in insulating capacity. Not surprisingly therefore, there has been continued interest in developing insulators that might be able to overcome the disadvantages of conventional textile materials and improve the mobility of the wearer by allowing the use of only a very thin layer of extremely-high insulating performance to provide the required thermal protection. One class of materials from which suitable candidates might be drawn is aerogels; their attractiveness derives from the fact that they show the highest thermal insulation capacity of any materials developed so far. Despite sporadic high levels of interest, commercialisation has been slow. Aerogels have been found to possess their own set of disadvantages such as fragility; rigidity; dust formation during working and cumbersome, expensive, batch-wise manufacturing processes. They may well have been destined to become a product of minor interest, confined to very specialist applications where cost was of little concern. However, methods have been developed to combine aerogels and fibres in composite structures which maintain extremely high insulating capacity whilst demonstrating sufficient flexibility for use in garments. Ways have been found to prevent the formation of powder as aerogel composite fabrics are worked. Most significant though, is the achievement, arising from a project supported by the Korean Government, of a simplified one-step production process developed with the express aim of providing a substantial reduction in the cost of aerogels. Suitably-priced aerogel is now available and this should provide fresh stimulus for research and development teams to engage in new product development work utilising aerogels in textiles and garments for thermal insulation. The mechanisms through which aerogels achieve their outstanding thermal insulating ability is unconventional, at least in terms of materials used in textiles. This issue of Textile Progress therefore includes detail about thermal transport in aerogels before reviewing the various forms in which aerogels can now be made, some of their applications and the research priorities that are now beginning to emerge.     

结构参数对超高分子量聚乙烯织物导热性的影响

为了提高服装热量的传导,采用导热率较高的超高分子量聚乙烯(UHMWPE)纱线作为纬纱与涤纶进行交织制成织物,并以电热片作为热源,通过铂电阻测温仪测量距离热源边界0、2、4 cm处织物表面温度随时间的变化。采用变量分离法测试纤维种类、纱线线密度、织物密度以及织物组织结构等因素对超高分子量聚乙烯织物导热性的影响。结果表明:含UHMWPE纱线交织物的导热性明显好于涤纶/涤纶和涤纶/锦纶交织物,且纱线越粗、织物密度越大、组织单元内纱线交织次数越少,织物导热性越好。     

Characterization and synthesis of polyester and viscose nonwovens fabrics embedded with nanoporous amorphous silica

Supreme thermal insulating properties of fibre composite can fortify its niche as a middle layer for numerous cold wear articles. Aiming to achieve lowest thermal conductivity, two separate nonwoven composites were successfully developed by using polyester and viscose fibres. Both were reinforced separately with in-house synthesized nanoporous amorphous silica via sol-gel processing using Tetraethoxy orthosilicate as a precursor with ambient pressure drying. Both nonwovens with two levels of GSM were subjected to silica sol for synthesis of nonwoven/SiO2 composite followed by solvent exchange, silylation and ambient pressure drying. The resulted structures were analyzed and evaluated for their thermal conductivity, pore size and characterized by The Fourier Transform Infrared spectroscopy and Scanning electron microscopy. Properties of composites were examined and compared to each level and attributes. Significant differences between the parameters were calculated using statistica v7.0. One of composite showed lowest thermal conductivity value 0.028 W/m.K     

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.     

4种家蚕茧壳的结构与性能

为开发设计新型功能纺织品,借助扫描电子显微镜、傅里叶红外光谱仪、X射线衍射仪、万能材料试验机和温湿度试验仪等研究了4种不同的家蚕茧壳的多层形貌、化学结构、结晶结构、力学性能和热传导性能,并对蚕茧壳的多层结构进行理论分析。结果表明:4种家蚕茧壳都具有独一无二的多层多孔结构,从外层到内层,纤维的直径先增大后减小;蚕茧壳厚度和尺寸不同,但都具有良好的热缓冲能力,相对而言,虎头蚕茧壳的耐热性最好,而斑马蚕茧壳(绿色)的热传导性最好。     

Modelling Thermal Conductivity in Heterogeneous Media with the Finite Element Method

Three-dimensional finite element simulations were developed to predict the effective thermal conductivity of theoretical composite materials having complex structures. The models simulated a steady-state thermal conductivity measurement device performing measurements on theoretical materials with varying structures. The structure of a composite was considered to be composed of some simplified basic models. When the geometry, orientation type and number of dispersion are specified, the computer randomly generated the position and orientation for each dispersion and created the geometrical model and finite element mesh. The effective thermal conductivity of the theoretical composite was calculated using this method and compared to the values obtained by simple effective thermal conductivity models methods. The influence of some factors such as the volume fraction and the ratio of the thermal conductivities of the heterogeneities and the surrounding material on the effective thermal conductivity is discussed.