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Fabric Waterproof and moisture permeability performance test
2018/11/14
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Waterproof and moisture permeable fabrics, also known as waterproof and breathable fabrics, are widely used in our daily life. This permeability to water vapor but resistance to water droplets are not only applied in textile industry but also can be employed in medical applications, membrane distillation, moisture regulation of buildings, and in humidification for the conservation of art and paper.1?4 They can be divided into high density woven fabrics, coated fabrics and laminated fabrics. The laminated fabric could display the excellent properties of all the component fabrics, and its multilayered structure is independent of each other and has good combination.Simultaneously, the processing technique of laminated fabric also avoids solvent pollution, labor protection and fire protection and other issues.
In recent years, nano fibers prepared by electro spinning technology have been used in filtration,5 sensors,6 tissue engineering7 and protective clothing.8 Electrospun nano fibrous membranes possess unique fabric construction, such as ideal porous structure with small pores, fine fiber diameter, large surface area and light weight, thus becoming the first choice for the preparation of multifunction and high-performance clothing fabrics.9 And the pore size of the electrospun nano fibrous membranes can be designed to be much smaller than the diameter of the smallest water droplets (2μm) and much larger than the diameter of the water vapor molecules (0.3~0.4μm). In addition, when laminated fabrics consisting of electrospun nano fibrous membranes it would be endowed good water vapor transmission capability due to the porous structure of the electrospun nano fibrous membranes. Based on the unique breathable characteristic, this laminated fabric is promising to construct protective clothing that the evaporation cooling process occurs in the pores of electrospun nano fibrous membranes.10?12 However, there are few reports on how to use electrospun nano fibrous membranes as functional layers for waterproof and moisture permeable laminated fabrics. In this study, polyester (PET) and polyurethane (PU) were directly spun on hot melt adhesive, and then they were hot pressed with fabric and lining to obtain laminated fabrics and its water resistance and vapor permeability were studied.
Experiments：
Materials
In this work, Nylon and cotton blended fabrics were used as shell fabric and warp knitted fabric was used as lining. Polyester (PET) and polyurethane (PU) were purchased from the Far Eastern Industry (Shanghai) Ltd., N, N-dimethylformamide (DMF), trifluoroacetic acid (TFA) and dichloromethane (DMC) are all analytical grade and were purchased from Beijing Tonguing Fine Chemicals Co., Ltd.,copolyamide (COPA) was used as hot-melt adhesives and purchased from Tangshan Fenghe Plastic Co., Ltd.. Electro spinning device was laboratory made.
Experimental process：
Preparation of electrospun nano fibrous membranes: Preparation of PET nano fibrous membranes: In this procedure, PET particles were dissolved in DMF and TFA (the volume ratio is 1:2) to form a 20% (by mass fraction, the same below) electro spinning solution.During the electro spinning process, the hot melt was coated on the receiver first, and then a high voltage of 20kV was applied to electro spin PET solution. The distance between the spinning nozzle and the receiver was 18 cm, the humidity was in the range of 10%~15% and the receiver rotation speed was 70r/min. Finally, PET nano fibrous membranes were obtained with different spinning time(4h, 6h, 8h, 10h and 12h), which were noted as PET 4, PET 6, PET 8, PET 10 and PET 12, respectively. The PU nano fibrous membranes were fabricated through a similar process. In this procedure, PU particles were dissolved in DMF to form 6% homogeneous electro spinning solution. The spinning voltage was 18kV, and the other conditions were the same as that of PET. Then PU nano fibrous membrane was obtained by spinning for 10h.
Preparation of laminated fabrics and determination of optimum hot pressing conditions: Copolyamide (COPA) was used as hot-melt adhesive during all the following hot pressing experiments. Firstly,the lining (sizing face upwards), and electros spun nano fibrous membrane,the shell fabric (sizing face downwards) were layered in turn on the hot machine. Then the different hot pressing time (15s, 17.5s, 20s,22.5s and 25s) and hot pressing temperature (100?C, 110?C, 120?C,130?C and 140?C) were set. The schematic diagram of hot pressing process for laminated fabrics is shown in Figure 1.
Performance testing of laminated fabrics: The morphology of COPA and electro spun nano fibrous membranes were characterized by scanning electron microscope (JSM-6360LV, Japan Electronics Co., Ltd.). The fiber diameter was gauged employing a custom code image analysis program (Smile View). Contact angle measurement:The sample was placed on a test bench of a video optical contact angle tester (OCA20, Data physics, Germany), the deionized water in the capillary was pushed at a rate of 2μL/s, and the image was frozen and the contact angle of the sample was analyzed by SCA20 software.
Air permeability (air resistance) test: Using an air resistance tester (KES-F8-AP1, KATO Company), the air resistance values of laminated fabrics and electrospun nano fibrous membranes were tested under a constant condition (humidity of 65% and temperature of 20?C) for 24h. The air resistance value [kPa/(s·m)] was taken the average of ten sampling point.
In order to determine the optimum hot pressing conditions, the peel strength of the laminated fabric was then measured by referring to criterion (FZ/T01010-1991) of “Coated fabrics-Determination method of coating adhesion”. A Fabric strength instrument (YGB026E-500,Wenzhou Dahong Textile Instrument Co., Ltd.) was used to test the peel strength of the laminated fabrics prepared by hot pressing. The size of test sample was fixed at 2.5cm×20cm. The tensile force and tensile distance was 300N and 10cm, respectively.
Waterproof and moisture permeability test: According to the criterion (GB/T4744-1997) of “Determination of hydrostatic resistance of impermeability of textile fabrics”, the hydrostatic pressure of laminated fabric was test under the following conditions using resistant hydrostatic pressure tester (SDLATLAS M018 Hydrostatic Head Tester, US SDL Atlas Ltd.). The water temperature was (20±2)?C, the increase rate of water pressure was 10cm H2O/min and the maximum water pressure was added up to 3000cm H2O.According to the criterion (GB/T12704.12009) of “Textile fabric moisture permeability test method Part 1: Moisture method”, the breathability of laminated fabrics were tested using moisture test device (DH-400, Japan Daejeon Scientific Institute of Fine Materials).During the testing, the air temperature was controlled at (38±2)?C, the relative humidity was controlled at (90±2)% and the fine-grained anhydrous calcium chloride was used as the desiccant.
Water absorption test: The sample was dried first at 38.5?C to get a constant weight, noted as W0 (g). Then immersed the samples in deionized water for 1h, took out the fabric and absorbed the surface water droplets with filter papers (the whole process should take no more than 1 min), weighted the fabric and recorded as W1 (g). The water adsorption capacity of fabric was calculated by the following equation:
Warmth retention of laminated fabrics was tested by KES-F7- II(Japan KATO TECH Co., Ltd.). Firstly, cutting the fabric into size of 20cm×20cm and keeping in a constant condition (humidity of 65% and temperature of 20?C) for 24h. Then, the warmth loss value was tested with and without fabric, respectively. Finally, the warmth retention value was calculated by the testing system.
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