Polypyrrole-Coated Zein/Epoxy Ultrafine Fiber Mats for Electromagnetic Interference Shielding

To reduce the environmental pollution and meet the needs for wearable electronic devices, new requirements for electromagnetic interference(EMI) shielding materials include flexibility, biodegradability, and biocompatibility. Herein, we reported a polypyrrole-coated zein/epoxy(PPy/ZE) ultrafine fiber mat which was inherently biodegradable and skin-friendly. In addition, it could maintain its ultrafine fibrous structure after coating, which could provide the mat with mechanical compliance, high porosity, and a large specific area for high EMI shielding. With the assistance of the epoxide cross-linking, the breaking stresses of the PPy/ZE fiber mats could achieve 3.3 MPa and 1.4 MPa and the strains were 40.1% and 83.0% in dry and wet states, respectively, which met the needs of various wearable electronic devices. Along with the extension in the PPy treatment duration, more PPy was loaded on the fiber surfaces, which formed more integrated and conductive paths to generate increasing conductivities up to 401.76 S·m^(-1). Moreover, the EMI shielding performance was raised to 26.84 dB. The biobased mats provide a green and efficient choice for EMI shielding materials, which may be a promising strategy to address EMI problems in multiple fields.

ELECTRO-THERMAL EFFECTS AND DEFORMATION RESPONSE OF CARBON FIBER MAT CEMENT BEAMS

A carbon fiber mat is a sheet composed of intercrossing short carbon fibers,which has more stable and lower electrical resistivity compared with dispersed short carbon fiber mixed in cement.Thereby carbon fiber mat cement could exhibit obvious electro-thermal effect.When electrified,the temperature of composite structures made up of cement mortar and carbon fiber mat will rise rapidly.If the temperature field is not uniform,temperature difference will cause structures to deform,which can be used to adjust the deformation of structures.The temperature field and deformation response driven by the electro-thermal effects of a type of carbon fiber mat cement beams are studied.Firstly,the temperature and deformation responses are studied using theories of thermal conduction and elasticity.Secondly,experimental results are given to verify the theoretical solution.These two parts lay the foundation for temperature and deformation adjustment.

Preparation of PVA/H_3PW_(12)O_(40) Fiber Mats

Poly(vinyl alcohol) (PVA) fiber mats containing 20 and 80 wt% H3PW12O40 were prepared by using electrospinning technique. The fiber mats were characterized by IR, XRD spectra and scanning electron microscope (SEM). The diameter of the fiber mats is ca. 400 nm.

Impregnation of thermoplastic resin in jute fiber mat

Impregnation rate of thermoplastic resin(polypropylene)in jute fiber mat and influence of relative factors on impregnation were studied,aiming to develop the continuous melt impregnation technique and to investigate the effect of impregnation rate and temperature on processing conditions and mechanical properties of natural fiber mat-reinforced thermoplastics.Influence of pressure on porosity of fiber mat and effect of melt viscosity on impregnation rate were also investigated.The modified capillary rheometer was used as apparatus and experimental data were analyzed based on the one-dimension Darcy’s law.Results showed that at a given pressure,the impregnation rate is inversely proportional to melt viscosity and jute fiber mat has higher porosity than glass fiber mat.The architecture,compressibility,permeability and fiber diameter of jute fiber mat were compared with those of glass fiber mat and their effects on impregnation were discussed further.It could be seen that the average diameter of jute fiber is much bigger;the porosity of jute fiber mat is significantly higher and inner bundle impregnation does not exist in jute fiber mat.Therefore,it is not difficult to understand why the impregnation rate in jute fiber mat is 3.5 times higher and permeability is 14 times greater.Kozeny constants of jute and glass fiber mats calculated based on the capillary model are 2950 and 442,respectively.

Highly Stretchable and Permeable Conductors Based on Shrinkable Electrospun Fiber Mats

Wearable on-skin electrodes or conductors should be vapor permeable,strain-insensitive,isotropically stretchable and stable under cyclic stretching.Various strategies have been proposed to prepare the required conductors up to now;however,it is a challenge to fabricate them with above properties in a simple manner.In this paper,a highly permeable and stretchable conductor based on electrospun fluorine rubber fiber mat is reported.The fibers are pre-stretched in electric field during electrospinning,and they shrink isotropically by~35-40%in area after being detached from the substrate.The obtained fiber mat conductor demonstrates high stretchability up to~170%,and the resistance changes only 0.8 under 60%strain,which is superior to many other strain-insensitive conductors.The conductor possesses high stability,no cracks or structure damage are observed after washing and cyclic stretching.Moreover,the conductor is vapor permeable with a water vapor transmission rate of~850 g m−2 day−1,which is comparable to the normal water evaporation in ambient conditions,indicating that it would not disturb the sweat evaporation when being used on skin.The conductor is successfully used as stretchable yarns and electromyography(EMG)electrodes,showing high reliability in E-textiles and on-skin applications.

Palladium nanoparticles supported on amine-functionalized glass fiber mat for fixed-bed reactors on the effective removal of hexavalent chromium by catalytic reduction

Palladium nanoparticles were deposited on the amine-grafted glass fiber mat （GFM-NH2） catalyst support by a conventional impregnation process followed by the borohydride reduction in aqueous solution at room temperature to create the designed Pd/GFM-NH2 catalyst. By the use of large size glass fiber mat without nano/mesopores as the catalyst support, the internal mass transfer limitations due to the existence of nano/mesopores on the catalyst support were eliminated and the Pd/GFM-NH2 catalyst could be easily separated from treated water due to the large size of the catalyst support. Batch experiments demonstrate its good catalytic reduction performance of Cr（VI） with formic acid as the reducing agent. It also demonstrated an efficient Cr（VI） removal and stability in a lab-prepared, packed fixed-bed tube reactor for the continuous treatment of Cr（VI）-containing water. Thus, it has a good potential for the catalytic reduction of Cr（VI） in the water treatment practice.

Chemomechanical Properties of Electrospun Polyvinyl Acetate(PVAc)Fiber Mat and its Application in Water-Triggered Self-folding

Environmental-stimulus-triggered self-folding mechanisms have found promising applications in many engineering fields.Recently,a water-activated self-folding procedure has been designed by using the electrospun polyvinyl acetate(PVAc)fiber mat which contains high tensile residual stresses in the vitrified fibers during the spinning processes.The water permeation initiates plasticization of PVAc fiber mat and leads to a material shrinkage.When water diffusion starts at the top surface of a PVAc sheet,a shrinkage variation along the diffusion pathway forms a bending hinge on the sheet,which has been demonstrated in 3D origami design.To capture the water-triggered plasticization mechanism and chemomechanical coupling deformation compatibility,a consistent finite deformation viscoplastic model is developed for the PVAc fiber mat under coupled chemomechanical loading conditions.The residual stress and‘fixed’strain are modeled through the unrecoverable plastic strain in the PVAc fiber mat.As water permeates into the PVAc fiber mat,the induced increase in mixing entropy lowers the glass transition temperature of the material,and results in a gradual relaxation of the fixed viscoplastic strain.A non-Fickian diffusion model suitable for glassy material is adopted to capture the water permeation in the PVAc fiber mat.After calibrated and validated by a series of experiments,the proposed model is implemented in ABAQUS software to simulate the water-activated self-folding of PVAc sheet.The numerical example for a typical origami design suggests a promising engineering application prospect.

石英纱线/石英纤维毡三维织物的设计及其隔热性能

为充分利用石英纱线及其纤维毡良好的隔热效果制备隔热性能优异的石英纱线/石英纤维毡三维织物,采用石英纱线和纤维毡在小样织机上进行三维立体编织,针对石英纱线/石英纤维毡三维织物不易编织等诸多问题,对织机综丝综框进行降低摩擦处理;然后采用控制变量法和实验对比法,对所得石英纱线/石英纤维毡三维织物在热环境下的隔热性能进行测试表征,对其加热状态下的温度和外观形状的变化趋势和规律进行探讨。实验结果表明:石英纱线/石英纤维毡三维织物在300~700℃时,平均隔热保留率是相等厚度普通石英纤维织物的4倍,验证了石英纱线/石英纤维毡三维织物的优越隔热性能。确定了石英纱线/石英纤维毡三维织物具有良好的整体性能和隔热性,能够作为航天飞行器的外部隔热材料抵挡高温冲刷,因此对石英纱线/石英纤维毡三维织物性能的研究具有深远意义。

复合增强型岩棉板的研发

以岩棉裸板为基材,配以专用的酚醛树脂(粘结剂)和无机玻纤毡,将表面处理后的带胶玻纤毡与岩棉板基体通过在线固化烘干工艺制备出复合增强型岩棉板。重点研究了复合增强型岩棉板的施工性能以及对岩棉板力学性能指标的影响。结果表明,复合增强型岩棉板在力学性能上得到显著提升,且板面的平整性、洁净性、耐磨性更为良好,更便于施工使用。

石膏板贴面毡用短切玻纤生产工艺介绍

石膏板贴面毡以短切纤维为原料,采用湿法成型工艺生产而成的一种用作石膏板贴面的薄毡。用于石膏板贴面毡的短切玻璃纤维有良好的分散性、连续的流动性及制品强度优异的特点。其生产方式可分为离线湿法短切及在线湿法短切。介绍了两种短切方式的特点及工艺流程,以及短纤分散性验证的方法。

双组分涤纶/玻璃纤维复合隔板的物理性能分析

为探索性能卓越且符合高性能电池使用要求的玻璃纤维复合隔板,将三种规格的双组分涤纶与玻璃纤维制成复合隔板,进行了纤维分散试验,测试了复合隔板的拉伸强度、抗穿刺强度、最大孔径与孔隙率,并与纯玻璃纤维隔板进行比较。结果表明:复合隔板的拉伸强度、抗穿刺强度能够达到纯玻璃纤维隔板的1倍以上,最大孔径可达16.04μm;1.67 dtex双组分涤纶与玻璃纤维制成的复合隔板具有较好的物理性能。在实际隔板生产时,建议双组分涤纶的配比为15%,生产温度为155~165℃。

铁碳纤维人工水草对污染河湖微生物挂膜的影响

针对水体强化净化过程中碳纤维人工水草表面能低、微生物附着时间长、挂膜启动慢的问题,利用废铁和碳纤维水草组合构建了铁碳纤维人工水草(ICF),以重污染地表水为原水,在阶段曝气的条件下进行了强化挂膜实验研究。结果表明,与碳纤维人工水草相比,铁碳纤维人工水草上生物膜的附着性能显著提升,生物膜的挂膜率由125.1%增加至133.0%,形成生物膜的团簇结构尺寸明显更大。启动期末(21 d)生物膜胞外聚合物中多糖、蛋白及蛋白/多糖比,分别由53,71 mg/gVSS、1.33改变为39,106 mg/gVSS、2.71。铁碳材料对假单胞菌属细菌的富集和筛选,改善了细菌的运动能力,促进了细菌分泌胞外聚合物的行为,此外,微生物活性功能基因在ICF中高度表达,提升了铁碳纤维材料表面微生物附着性能。

Effect of Needle Punching Process on a Chopped Strand Mat Composite with an Open Hole

The easiest and most reliable joining method is the mechanical joint with a bolt and nut or rivet. However, in the case of composite laminates, mechanical joint properties decrease because of lower interlaminar properties compared to in-plane properties around hole.?This study investigated needle punching process with the aim of improving the mechanical properties in the thickness direction of fiber-reinforced plastic composite laminates with an open hole. Needle punching process was applied to glass fiber chopped strand matused as the reinforcement for the composite laminates. Open-hole tensile tests and observations of end cross-sections after the tests were performed. The tensile properties and fracture mechanism of the specimens subjected to needle punching process were investigated. In addition, characteristic distance (a parameter for evaluating resistance to fracture in open-hole tensile test specimens) was also calculated to examine the effects of needle punching process conditions on fracture toughness. Tensile strength was improved by more than 15% by needle punching process. However, when a certain needle punching density was exceeded, the mechanical properties worsened. In addition, characteristic distance increased with increasing needle punching density. Thus, these results suggest that there is an optimal needle punching density with respect to strength and characteristic distance.

加筋长纤聚酯毡与长纤聚酯毡的性能对比及对改性沥青卷材生产过程的影响

对比了加筋长纤聚酯毡与普通长纤聚酯毡的性能,分析了以两者为胎基生产的同规格改性沥青防水卷材的性能以及在不同混合料黏度、生产线速度情况下生产的卷材的尺寸稳定性。结果表明,相同规格的加筋长纤聚酯毡指标优于普通长纤聚酯毡,具有更好的尺寸稳定性;在相同的生产条件下,以加筋长纤聚酯毡为胎基能够提高改性沥青防水卷材的生产效率、提升产品质量、降低生产成本。

玻纤复合毡在玻璃熔窑中的应用

通过分析玻璃熔窑工况特点、排放粉尘粒径情况,分析了PPS化纤毡滤料、PTFE化纤毡滤料及玻纤复合毡滤料的纬向强力及耐酸性能,探索了使用玻纤复合毡滤料替代PTFE化纤毡滤料在玻璃熔窑上的可行性。

带锚固端BFRP筋-混凝土的粘结性能试验与本构模型研究

BFRP筋是一种可取代钢筋用于海洋工程的新型增强材料,具有广阔的应用前景。针对BFRP筋在混凝土结构中粘结强度不足的问题,采用碳纤维布锚固的方法改善BFRP筋-混凝土粘结性能,从而提高BFRP筋与混凝土的协同作用。该文通过20个中心拉拔试件,分析了碳纤维锚固长度、锚固直径及混凝土强度对试件粘结-滑移性能和破坏形态的影响。结合试验结果对现有模型的粘结特征参数进行修正,提出碳纤维布锚固条件下BFRP筋-混凝土的粘结强度计算公式,建立一种BFRP筋-混凝土粘结滑移本构模型。结果表明:碳纤维锚固端可以有效的提高粘结性能,限制混凝土开裂,提高残余粘结强度,充分发挥BFRP筋的增强作用;混凝土强度是影响锚固性能的主要因素;随着锚固长径比的提高,碳纤维的锚固性能逐渐提升。

我国玻璃纤维粉末粘结剂的研究进展

对国内近些年不同结构的玻璃纤维粉末粘结剂进行总结,可根据产品的生产工艺、应用领域来选择合适的粉末粘结剂,以达到所需的使用效果。随着应用领域逐渐拓展,玻璃纤维短切毡的性能要求越来越高,开发高强度、快浸透、覆模性好等综合性能好的粉末粘结剂仍具有广阔的应用前景。

玻纤网格增强聚酯毡在改性沥青防水卷材中的应用研究

研发了一种玻纤网格增强聚酯毡,介绍了其结构特点和生产工艺。与其他类型的聚酯毡材料相比,玻纤网格增强聚酯毡在热尺寸稳定性方面具有明显优势。在相同生产条件下,以玻纤网格增强聚酯毡为胎基制备的改性沥青防水卷材性能指标符合标准要求,并且可以大幅提升生产速度从而大幅提高生产效率,降低生产成本。

TiO_2负载玄武岩纤维毡复合材料的制备及其光催化性能

采用浸渍法将热蚀处理后的玄武岩纤维毡浸渍在Ti溶胶中负载成膜,在300-650℃烧结制备出TiO2负载玄武岩纤维毡光催化复合材料。利用XRD和SEM对TiO2和纤维毡进行了表征,并通过甲基红配制的模拟印染废水的降解考察了浸渍次数和烧结温度对光催化性能的影响。实验表明：随着玄武岩纤维毡在Ti溶胶中浸渍次数的增加,TiO2负载率增加,甲基红降解率具有先急剧增加后缓慢减小的趋势,TiO2负载率为4.83%时降解率达到极值98.58%。随着烧结温度升高,TiO2晶型由无定形态→锐钛矿→锐钛矿＋金红石混晶转变,当锐钛矿与金红石混晶比例为9∶1-4.5∶1时,光催化性能较好,随着金红石相增加,甲基红降解率大幅降低。