Cross-electrospun PVDF/PVDF-HFP nanofibrous membrane with central combination design and its waterproof and moisture permeable composite fabric

Abstract

Waterproof and moisture permeable composite fabric with electrospun nanofibrous membrane has been widely used, because of its high specific surface area, high porosity, small pore size, uniform pore distribution and light weight. However, there are fewer studies on fabricating waterproof and permeable composite fabric with optimal polyvinylidene fluoride/polyvinylidene fluoride hexafluoropropylene electrospun nanofibrous membrane by multi-needle cross-electrospinning technology and hot-press process. In this study, excellent waterproof and moisture permeable polyvinylidene fluoride/polyvinylidene fluoride hexafluoropropylene electrospun nanofibrous membranes with the optimal process conditions were prepared through central combination design with Design Expert 8.0.5 and experimental validation. The composite fabrics with three different adhesives were prepared. The contact angle, waterproof and moisture permeability, and mechanical properties of composite fabrics were tested. The results showed that CF-1 had better performance with high hydrostatic pressure of 9840 mmH₂O, strong moisture permeability of 10,280 g · m⁻² · d⁻¹, and excellent peel strength and tensile tenacity. It was of great significance to realize the industrial production of waterproof and breathable composite fabric with electrospun nanofibrous membrane by multi-needle cross-electrospinning technology and hot-press process.

Keywords

Cross-electrospun nanofibrous membrane composite fabric waterproof and moisture permeability central combination design

In recent years, waterproof and moisture permeable fabrics have been widely used and become a research hotspot.^1,2 During wearing, water does not penetrate the textiles under a certain pressure, but the sweat emitted by the human body can pass through the fabric or in the form of water vapor, so as to realize the comfort of wearing.³ Therefore, waterproof and moisture permeable fabrics are widely used in the field of outdoor clothing. High-density ventile, waterproof and moisture permeable fabric was first developed by the Shirley Institute in the UK in the 1940 s. The fabric with good moisture and air permeability and low water pressure resistance was mainly used for cold and water-resistant clothing for Air Force pilots.⁴ Later, polyurethane (PU) coated microporous membrane fabric and polytetrafluoroethylene (PTFE) laminated composite fabric with microporous membrane were widely popular in the market. The GORE company of the United States in 1965 developed GORE-Tex fabric,⁵ which was the most representative of PTFE laminated composite fabric with waterproof and moisture permeability. With the continuous improvement of the performance requirements for waterproof and moisture permeable fabric, its application was more and more widespread, from traditional clothing to medical⁶ and military special industries.^7–10

At present, waterproof and moisture permeable membrane can be divided into two categories: porous and nonporous. Thermoplastic polyurethane (TPU) membrane made by the blowing method is the mainstream product, but it has no porosity, resulting in low air permeability and moisture permeability, which cannot meet the requirements of high moisture permeable fabrics. Because of its high specific surface area, high porosity, small pore size, uniform pore distribution and light weight,^11–13 electrospun nanofibrous membrane (ENM) is composed of nanoscale fiber, which has been widely used in nanowaste environmental treatment,^14,15 filtration, photochemical sensors, biotechnology and energy fields.^16–18 The ENM has a three-dimensional (3D) network structure, which allows water vapor to pass freely when there is a difference in humidity inside and outside, and can prevent water droplets from passing through, resulting in the better waterproof and moisture permeability. Therefore, ENM has attracted the attention of both academia and industry.^19–24

Electrospinning technology is a method to fabricate micro/nano fibers from electrostatically charged polymer fluids under the electrostatic field,²⁵ which is similar to the electric field-driven microscale 3D printing technology.^26,27 Cross-electrospinning is used to prepare and significantly improve the tenacity of ENM, the mechanism of which is that, for example, in total four needles are employed during the electrospinning process, with two needles containing one solution and the other ones containing other solutions, respectively. They are arranged along the spinneret such that every other needle was used to electrospin different polymer solutions alternately. The hot-press process is a method to combine two materials under a certain pressure and temperature, resulting in making an even and high-performance material.²⁸ The hot-press process is easy to operate and can offer melt-bonding function to improve the strength of ENM,^29,30 with the help of low melting point polymers. Polyvinylidene fluoride (PVDF) has been widely used as a waterproof and moisture permeable material, because of its low price, high toughness, good impact strength and wear resistance, and excellent hydrophobic performance, which is very suitable for preparation of ENM by electrospinning technology.^31,32 Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) is a thermoplastic polymer with a lower melting point and equal properties of PVDF. There is a number of studies about PVDF and PVDF-HFP as new materials, due to their low surface energy.^33–36 While there are fewer studies on exploring their optimal process parameters and response values with the central combination design (CCD) of response surface methodology (RSM), which is a statistical method quickly to determine optimal process parameters and effectively solve multiple problems.^37,38 The basic principle of CCD of RSM is to establish a function model of the quantitative relationship between the research result Y and the experimental multiple factors. According to this model, the effect surface can be described, and the independent variable value corresponding to the effect value can be found from the effect surface, so as to obtain better experimental conditions. CCD has been rapidly developed and widely used in the chemical industry, biology, medicine, pharmaceuticals³⁹ and food science⁴⁰ and other fields,⁴¹ because of its continuous prediction model and simple calculation for effectively solving practical problems and other advantages. It will make sense to apply it to the textile field to explore the optimal process parameters and response values.

In order to obtain an ENM with good mechanical strength, excellent waterproof and moisture permeability by a simple preparation method, PVDF/PVDF-HFP ENM was first fabricated by multi-needle cross-electrospinning technology and hot-press process. The waterproof and moisture permeability of optimized PVDF/PVDF-HFP ENM after the CCD method had been compared with the experimental and theoretical value. Through the comparison of results of fiber morphology, fiber diameter, pore size distribution, porosity and water contact angle (WCA), the influence of the optimized process on the waterproof and moisture permeability of the membrane was verified. Finally, the ENM and Chunya-Spun twill fabric were combined with different adhesives to prepare the composite fabric with excellent waterproof and moisture permeability, which could be comparable with Gore-Tex, showing great potential for practical application.

Experimental section

Materials

PVDF with molecular weight of 1,000,000 was purchased from Solvay in the United States. PVDF-HFP with molecular weight of 600,000 was provided by DuPont. N, N-dimethylformamide (DMF, 99.7% in purity) and acetone (99.7% in purity) were purchased from Tianjin Fuchen Chemical Reagent Factory. Polyester based Chunya-Spun twill fabric (PET fabric) was purchased from Wujiang Shengdi Textile Co. Ltd. Reactive polyurethane adhesive was supplied by Shanghai Kangda Chemical New Materials Co. Ltd. Copolyamide adhesive was provided by Shanghai Tianyang Hot Melt Adhesive Co. Ltd. Water-soluble polyurethane adhesive was purchased from Dongguan Yibao Resin Co. Ltd. All materials were used without further purification.

Preparation of PVDF/PVDF-HFP ENM

PVDF (9 wt.%) and PVDF-HFP (13 wt.%) powders were added into DMF/acetone (mass ratio 7:3) mixed solvent system, respectively, and stirred at room temperature on a magnetic stirrer. After 10 h, colorless transparent viscous solutions were obtained, as PVDF and PVDF-HFP spinning solutions. PVDF/PVDF-HFP ENM with weight of 25 ± 2 g · m⁻² were collected 20 cm apart from the needle tip on grounded metallic roller with speed of 60 r min⁻¹ under 35 kV voltage by multi-needle cross-electrospinning technology, as shown in Figure 1. The feeding rate of PVDF and PVDF-HFP was 1.5 mL · h⁻¹ and 1 mL · h⁻¹, respectively. The mass ratios of PVDF and PVDF-HFP ENM were 1, 2, 3, 4 and 5. The model of spinning needle for electrostatic spinning was no. 20, purchased from Beijing Shiyong Technology Co. Ltd. The electrostatic spinning equipment was self-made by the laboratory, the High-voltage DC power supply was purchased from Tianjin Dongwen High-voltage Power Supply Factory, the SK-500IIIB six-channel micro-injection pump was purchased from Shenzhen Shenke Medical Equipment Technology Development Co. Ltd., and the 57HS09 two-phase stepper motor/M542 two-phase driver was the product of Shenzhen Leisai Intelligent Control Co. Ltd.

Figure 1.

Schematic diagram of composite fabric with polyvinylidene fluoride (PVDF)/polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) electrospun nanofibrous membrane (ENM) and adhesive by cross-electrospinning technology and hot-press process, in which two needles contained PVDF solution and the others contained PVDF-HFP solution, respectively.

CCD experiment

In order to explore the optimal experimental conditions of hot-press process, the CCD experiment was used with the following four variables: mass ratio (A), hot-press temperature (B), hot-press pressure (C), and hot-press time (D) for the hydrostatic pressure and moisture permeability of the response value. Mass ratio was the mass ratio of PVDF to PVDF-HFP in spinning solution. Hot-press temperature, hot-press pressure, and hot-press time represented the required parameters of ENM during the hot-press process. The melting point of PVDF-HFP is between 110°C and 150°C, while the melting point of PVDF is 170°C. To improve the mechanical property of ENM with part-melted PVDF-HFP, the range of the hot-press temperature was determined at the melting point of PVDF-HFP. As for time and pressure, the fabricated speed and quality of ENM were the choice standard after experimental results. According to the obtained experimental parameters, the central combined experiment was designed with Design Expert 8.0.5 software. The four factors and five levels of hot-press process are shown in Table 1.

Table 1.

Four factors and five levels of hot-press process

Factors	Levels
Mass ratio	1	2	3	4	5
Temperature (°C)	130	135	140	145	150
Pressure (MPa)	0.3	0.4	0.5	0.6	0.7
Time (Min)	2	4	6	8	10

Preparation of waterproof and moisture permeable composite fabric

Waterproof and moisture permeable composite fabrics were compounded with optimal PVDF/PVDF-HFP ENM and PET fabric through three different adhesives, which were named CF-1, CF-2, and CF-3, respectively, as shown in Figure 1. PET fabric was compounded with an amount of 4 g · m⁻² reactive polyurethane adhesive at 100°C by the hot-melt transfer method, and then, CF-1 was obtained after a curing time of 24 h under room temperature and humidity of 55%. CF-2 was compounded with PET fabric and an amount of 12 g · m⁻² copolyamide hot-melt net at 130°C under pressure of 2 MPa for 15 s by hot-press process. PET fabric was compounded with an amount of 4 g · m⁻² water-soluble polyurethane by scratch coating and air-blow drying at 80°C for 2 min, and then, the CF-3 was obtained at 90°C under pressure of 2 MPa for 10 s by hot-press process.

Characterization

The surface morphologies of the ENMs were observed on a Nippon Electronics JSM6510 scanning electron microscope (SEM). The fiber diameters of ENMs were measured by the software of Image Pro Plus on the recorded SEM photos. At least 50 nanofibers from each sample were randomly selected and analyzed. The pore sizes of the ENMs were recorded with a gas-liquid pore diameter analyzer (CFP-1500A PMI), under the pressure of 0-60 psi. The WCA of ENMs was recorded by Theta Flow CA tester (Biolin, Finland). Porosity (ε) is the fraction of the volume of voids over the total volume of ENM, which can be calculated with equation (1) as follows:

ε = (1 - \frac{M}{π \times \frac{D^{2}}{4} \times T \times Bulk density of PVDF / PVDF - HFP}) \times 100 %

(1)

where: M is the mass weight of samples; D is the fiber diameter of circular nanofiber samples; T is the thickness of samples; the bulk density of PVDF/PVDF-HFP was 1.785 g · cm⁻³.

The hydrostatic pressure of ENMs and composite fabrics were determined on a hydrostatic pressure tester SDL Atlas according to ASTM E96 standard. The moisture permeability of ENMs and composite fabrics were measured on LYG-216 fabric moisture permeability tester (Shandong Textile Research Institute) according to ASTM E96-2005 (BW). The tensile strength of ENMs and composite fabrics were recorded on INSREON-3699 universal strength machine according to ASTM D5034 standard. The peeling strength of composite fabrics was recorded on INSREON-3699 universal strength machine according to GB/T 2791-1995 standard. The effective peel length was 100 mm, and the peel rate was 100 mm · min⁻¹. Each reported value was the average of five valid specimens.

Results and discussion

Experimental results of CCD

Expert Design 8.0.5 software was used with the central combination experimental scheme for the preparation of optimal ENM. According to specific experimental conditions, response values (hydrostatic pressure and moisture permeability) of ENM were tested, which are summarized in Supplementary Table 1.

Analysis for waterproof performance of PVDF/PVDF-HFP ENM

Multivariate quadratic regression equation fitting

The software Design Expert 8.0.5 was used for regression analysis of the experimental data, and the multivariate quadratic regression equation of each factor on the hydrostatic pressure of the response value was finally obtained:

\begin{array}{l} H = 7586.98 + 82.87 * A - 350.75 * B + 847.25 * C \\ - 423.58 * D - 162.25 * A * B - 92.25 * A * C \\ - 174.75 * A * D - 256.50 * B * C - 177.50 * B * D \\ + 434.50 * C * D - 16.52 * A^{2} - 531.08 * B^{2} \\ - 441.08 * C^{2} + 475.92 * D^{2} \end{array}

(2)

where H is:hydrostatic pressure value, A is mass ratio, B is temperature, C is pressure, and D is time.

The variance analysis results of multiple quadratic regression equation (2) are shown in Table 2. Table 2 shows that the P value of the model was less than 0.0001, indicating that the regression model was significant. The P value of the missing term was 0.1745 (>0.05), which proved that the above model was effective. The fitting degree of the model was 93.64%, which proved that the variable factors in the regression equation accounted for 93.64% of the total factors affecting the hydrostatic pressure of ENM. The calibration fit of 87.7% proved that the model was significantly effective. The response value of signal-to-noise ratio reflected high accuracy of data. In this design, the value of the signal-to-noise reached 17.409 (>4), which proved that the model had significant discrimination ability. The small coefficient of variation (7.19%) proved the high accuracy of the model’s output data.

Table 2.

Variance analysis for waterproof performance of ENM

Factor	Sum of squares	Degree of freedom	Mean square	F value	P value
Model	5.922 × 10⁷	14	4.230 × 10⁶	15.77	<0.0001
A	3.517 × 10⁵	1	3.517 × 10⁵	1.31	0.0271
B	2.147 × 10⁶	1	2.147 × 10⁶	8.01	0.0127
C	1.253 × 10⁷	1	1.253 × 10⁷	46.72	<0.0001
D	3.132 × 10⁶	1	3.132 × 10⁶	11.68	0.0038
AB	1.685 × 10⁶	1	1.685 × 10⁶	6.28	0.0242
AC	5.446 × 10⁵	1	5.446 × 10⁵	2.03	0.1746
AD	1.954 × 10⁶	1	1.954 × 10⁶	7.29	0.0165
BC	1.053 × 10⁶	1	1.053 × 10⁶	3.93	0.0662
BD	5.041 × 10⁵	1	5.041 × 10⁵	1.88	0.1905
CD	3.021 × 10⁶	1	3.021 × 10⁶	11.26	0.0043
A²	1.198 × 10⁵	1	1.198 × 10⁵	0.45	0.5141
B²	7.736 × 10⁶	1	7.736 × 10⁶	28.85	<0.0001
C²	5.336 × 10⁶	1	5.336 × 10⁶	19.90	0.0005
D²	6.212 × 10⁶	1	6.212 × 10⁶	23.17	0.0002
Residual	4.022 × 10⁶	15	2.682 × 10⁵
Lack of fit	3.326 × 10⁶	10	3.326 × 10⁵	2.39	0.1745
Pure error	6.965 × 10⁵	5	1.393 × 10⁵
Total variation	6.324 × 10⁷	29
Fitting degree	0.9364		Corrected fit	0.8770
Signal-to-noise ratio	17.409		Coefficient of variation	7.19%

ENM: electrospun nanofibrous membrane.

Significance analysis for waterproofing performance with single factor effect

The results in Table 2 show that the P values of four factors A, B, C and D were all less than 0.05. It indicates that these four factors had a significant impact on the hydrostatic pressure of the response value. The significance of influence could be determined by the P value: C > D > B > A. Figure 2 shows the influence trend of the four factors on response values. In Figure 2, the response values were within the upper and lower limits of the confidence interval, indicating that the regression simulation was normal.

Figure 2.

Influence trends of mass ratio (a), temperature (b), pressure (c) and time (d) on hydrostatic pressure of response values, where the upper blue curves stand for the maximal limits of the confidence intervals, and the lower blue curves represent the minimal limits of the confidence intervals, and the central black curves indicate the predicated values, respectively.

In Figure 2(a), when the other three factors remained unchanged, the hydrostatic pressure of ENM increased first and then decreased, with the increase of the mass ratio. As a result of the decease of the PVDF-HFP level, the pore size and porosity of ENM after hot-press process had decreased, resulting in the rise of hydrostatic pressure. When the mass ratio continued to increase, the level of PVDF-HFP became much lower. Because of the lower adhesion points, the pore size and porosity of ENM after hot-press process were increased. Therefore, the final hydrostatic pressure of response value gradually decreased. In Figure 2(b), when the other three factors remained unchanged, the hydrostatic pressure of ENM increased first, and then decreased with the increase of temperature. Due to the increase of temperature, the pore size and porosity of ENM after hot-press process had decreased, resulting in the rise of hydrostatic pressure. As the temperature continued to increase, the thickness and contact angle of ENM decreased due to the excessive degree of hot-press. Therefore, the final hydrostatic pressure of the response value gradually decreased. In Figure 2(c) and (d), when the other three conditions remained unchanged, the hydrostatic pressure of ENM increased first, and then decreased, with the increase of pressure or time. As the adhesion points gradually increased, the pore size and porosity of ENM after hot-press process had decreased, resulting in the rise of hydrostatic pressure.

Significance analysis for waterproofing performance with interactive effect

The interaction between the two factors could clearly reflect the change information of the response value with the binary variables in the 3D space, which could be used to explain the optimization scheme of the experiment theoretically. The partial regression coefficient of significance test in the regression equation (2) showed that P values of mass ratio temperature, mass ratio time, pressure time were less than 0.05, which indicated that there were significant interaction effects. The contour plots and response surface plots of hydrostatic pressure with three groups of significant interactive effect are shown in Figure 3.

Figure 3.

Contour plots (a), (c), (e) and response surface plots (b), (d), (f) of hydrostatic pressure with mass ratio temperature, mass ratio time and pressure time.

In Figure 3(a) and (b), when the mass ratio was small, the hydrostatic pressure of ENM increased first, and then decreased with the increase of temperature. When the mass was large, the hydrostatic pressure also increased first, and then decreased with the increase of temperature. It demonstrated that the required temperature of hot-press process changed for mass ratio, resulting in changes of hydrostatic pressure of response. In Figure 3(c) and (d), when the mass ratio was small, the hydrostatic pressure increased slowly at first, and then decreased rapidly with the increase of temperature. When the mass ratio was large, the hydrostatic pressure increased rapidly at first, and then decreased slowly with the increase of temperature. With the high level of PVDF-HFP, it took a long time to form enough bonding points to improve the strength of the ENM. Once the optimal time was exceeded, the hydrostatic pressure decreased rapidly due to a large number of PVDF-HFP with excessive heat. When PVDF-HFP fiber level was small, hot-press process can improve hydrostatic pressure in a short time. With the continued decrease of the PVDF-HFP level, the overall strength of the membrane decreased slowly, resulting in a slow decrease of the hydrostatic pressure. In Figure 3(e) and (f), when the pressure was high, the hydrostatic pressure increased first, and then decreased with the increase of time. The changing rate of hydrostatic pressure per unit time was large. When the pressure was high, the speed of heat transfer in the membrane was improved, and its influence was also highlighted quickly.

Analysis for moisture permeability of PVDF/PVDF-HFP ENM

Multivariate quadratic regression equation fitting

The software Design Expert 8.0.5 was used for regression analysis of the experimental data, and the multivariate quadratic regression equation of each factor on the moisture permeability of the response value was finally obtained:

\begin{array}{l} Q = 8859.94 + 326.85 * A - 482.58 * B + 315.73 * C \\ + 406.31 * D - 169.72 * A * B + 215.80 * A * C \\ + 97.95 * A * D + 547.30 * B * C - 404.40 * B * D \\ - 601.25 * C * D - 50.18 * A^{2} + 419.68 * B^{2} \\ + 350.68 * C^{2} + 97.28 * D^{2} \end{array}

(3)

where Q is moisture permeability, A is mass ratio, B is temperature, C is pressure, and D is time.

The variance analysis results of multiple quadratic regression equation (3) are shown in Table 3. Table 3 shows that the P value of the model was less than 0.05, indicating that the regression model was significant. The P value of the misfitting term was 0.1650 (>0.05), which proved that the above model was effective. The fitting degree of the model was 87%, which proved that the variable factors in the regression equation accounted for 87% of the total factors affecting the moisture permeability of ENM. The fitting degree of correction was 84.21%, indicating that the model was relatively effective. In this design, the value of signal-to-noise reached 8.572 (>4), which proved that the model had significant discrimination ability. The small coefficient of variation (9.52%) proved the high accuracy of the model’s output data.

Table 3.

Variance analysis of moisture permeability of ENM

Factor	Sum of squares	Degree of freedom	Mean square	F value	P value
Model	5.639 × 10⁷	14	4.028 × 10⁶	34.67	0.0027
A	5.470 × 10⁶	1	5.470 × 10⁶	47.08	0.0043
B	4.065 × 10⁶	1	4.065 × 10⁶	34.99	0.0061
C	1.740 × 10⁶	1	1.740 × 10⁶	14.98	0.0356
D	2.882 × 10⁶	1	2.882 × 10⁶	24.81	0.0159
AB	1.844 × 10⁶	1	1.844 × 10⁶	15.87	0.0012
AC	2.980 × 10⁶	1	2.980 × 10⁶	25.66	0.5649
AD	6.140 × 10⁵	1	6.140 × 10⁵	5.29	0.5979
BC	4.793 × 10⁶	1	4.793 × 10⁶	41.26	0.0179
BD	2.617 × 10⁶	1	2.617 × 10⁶	22.53	0.1852
CD	5.784 × 10⁶	1	5.784 × 10⁶	49.79	0.9103
A²	1.105 × 10⁶	1	1.105 × 10⁶	9.51	0.0823
B²	4.831 × 10⁶	1	4.831 × 10⁶	41.59	0.0150
C²	3.373 × 10⁶	1	3.373 × 10⁶	29.04	0.0365
D²	2.595 × 10⁵	1	2.595 × 10⁵	2.23	0.0930
Residual	1.742 × 10⁶	15	1.162 × 10⁵
Lack of fit	1.449 × 10⁶	10	1.449 × 10⁵	2.48	0.1650
Pure error	2.933 × 10⁵	5	5.866 × 10⁵
Total variation	5.813 × 10⁷	29
Fitting degree	0.8700		Corrected fit	0.8421
Signal-to-noise ratio	8.572		Coefficient of variation	9.52%

ENM: electrospun nanofibrous membrane.

Significance analysis for moisture permeability with single factor effect

The results in Table 3 show that the P values of four factors A, B, C and D were all less than 0.05. It indicates that these four factors had a significant impact on the moisture permeability of the response value. The significance of influence could be determined by the P value: A > B > D > C. Figure 4 shows the influence trend of the four factors on response values. In Figure 4, the response values are within the upper and lower limits of the confidence interval, indicating that the regression simulation was normal.

Figure 4.

Influence trends of mass ratio (a), temperature (b), pressure (c) and time (d) on moisture permeability of response values, in which the upper blue curves standing for the maximal limits of the confidence intervals, and the lower blue curves represent the minimal limits of the confidence intervals, and the central black curves indicate the predicated values, respectively.

In Figure 4(a), when the other three factors remained unchanged, the moisture permeability of ENM increased with the increase of the mass ratio. As a result of the decease of the PVDF-HFP level, pore size and porosity of ENM after hot-press process had increased, resulting in the rise of moisture permeability. In Figure 4(b), when the other three factors remained unchanged, the moisture permeability of the fiber membrane decreased with the increase of temperature. As a result of the increase of melt PVDF-HFP nanofiber at higher temperature after hot-press process, the pore size and porosity of ENM had decreased, resulting in the decrease of moisture permeability. In Figure 4(c), when the other three factors remained unchanged, the moisture permeability of ENM decreased first, and then increased with the increase of pressure. When the pressure was low, the decrease of pore size and porosity made the moisture permeability decrease. When the pressure continued to increase, the thickness of ENM after hot-press process was decreased, Therefore, the final moisture permeability of the response value gradually increased. In Figure 4(d), when the other three factors remained unchanged, the moisture permeability of ENM increased first, and then decreased with the increase of time. When time was short, the contact angle of the ENM decreased, so the moisture permeability increased. When time continued to increase, pore size and porosity of ENM after hot-press process had decreased, resulting in the decrease of moisture permeability.

Significance analysis for moisture permeability with interactive effect

The partial regression coefficient of significance test in the regression equation (3) showed that P values of mass ratio temperature, temperature pressure were less than 0.05, which indicated that there were significant interaction effects. The contour plots and response surface plots of moisture permeability with two groups of significant interactive effects are shown in Figure 5.

Figure 5.

Contour plots (a) and (c) and response surface plots (b) and (d) of moisture permeability with mass ratio temperature and temperature pressure.

In Figure 5(a) and (b), when the mass ratio was small, the moisture permeability of ENM decreased rapidly with the increase of temperature. When the mass ratio was large, the moisture permeability decreased slowly with the increase of temperature. When the mass ratio was small, pore size and porosity of ENM with a high level PVDF-HFP by hot-press process could be changed at a relatively low temperature, resulting in the rapid change rate of moisture permeability. On the contrary, when the mass ratio was large, the PVDF-HFP level was small, and the change of ENM’s structure by hot-press process required a higher temperature, resulting in the slow change rate of moisture permeability. In Figure 5(c) and (d), when temperature was constant, the moisture permeability of ENM decreased first, and then increased with the increase of pressure. When temperature was lower, the change degree of the moisture permeability of ENM was smaller, because of the heat transfer in a large pressure.

Experimental validation for waterproof and moisture permeability of ENM

With help of Expert Design 8.0.5 software, the optimal experimental conditions for waterproof and moisture permeability of ENM could be obtained as follows: mass ratio was 2.96; hot-press temperature was 139°C; hot-press pressure was 0.57 MPa; hot-press time was 7.25 min. According to the optimized experimental conditions, the results of hydrostatic pressure and moisture permeability of ENM are shown in Figure 6.

Figure 6.

Comparison on waterproof performance (a) and moisture permeability (b) of electrospun nanofibrous membrane (ENM) between experimental and theoretical value.

As can be seen from Figure 6, the predicted hydrostatic pressure resistance and moisture permeability were 8690 mmH₂O and 10900 g · m⁻² · d⁻¹, respectively. While those of ENM with optimized experimental value were 8460 mmH₂O with a small relative error of 2.72%, and 11,130 g · m⁻² · d⁻¹ with a small relative error of 2.01%, respectively. It proved that the fitting degree of the model was high and met the experimental requirements. In Figure 6, the hydrostatic pressure of the ENM increased from 7310 mmH₂O to 8460 mmH₂O in optimized experimental conditions. The moisture permeability of ENM increased from 9710 g · m⁻² · d⁻¹ to 11,130 g · m⁻² · d⁻¹ in optimized experimental conditions. It indicated that the waterproof and moisture permeability of ENM could be significantly enhanced and relatively stable with a small fluctuation range after the central composite design.

In order to explain better the excellent waterproof and moisture permeability of the optimized PVDF/PVDF-HFP ENM, the SEM images, average fiber diameter, pore size distribution, porosity and WCA of the ENM before and after optimization was tested, as shown in Figure 7, and the corresponding data are summarized in Table 4. From Figure 7(a) and (b), the unoptimized PVDF/PVDF-HFP ENM were flat, thick, and excessively bonded together. While the optimized PVDF/PVDF-HFP ENM were uniform, thin and round. In Figure 7(c) and (d), the fiber diameter of the optimized PVDF/PVDF-HFP ENM was only 750 nm, which was 27.1% smaller than that of the unoptimized PVDF/PVDF-HFP ENM. The unoptimized PVDF/PVDF-HFP ENM with too much melting of PVDF-HFP was in a random process condition in which the hot-press time was too long or the hot-press temperature was too high, resulting in the larger fiber diameter. From Figure 7(e) and (f) and Table 4, the optimized PVDF/PVDF-HFP ENM had the smaller pore size, the higher porosity and the bigger WCA, which could verify that the optimized PVDF/PVDF-HFP ENM had better waterproof and moisture permeability, compared with unoptimized PVDF/PVDF-HFP ENM.

Figure 7.

(a) Scanning electron microscope (SEM) photo of unoptimized polyvinylidene fluoride (PVDF)/polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) electrospun nanofibrous membrane (ENM); (b) SEM photo of optimized PVDF/PVDF-HFP ENM; (c) the distribution of fiber diameter of unoptimized PVDF/PVDF-HFP ENM; (d) the distribution of fiber diameter of optimized PVDF/PVDF-HFP ENM; (e) the distribution of pore size of PVDF/PVDF-HFP ENM and (f) the porosity and water contact angle (WCA) of PVDF/PVDF-HFP ENM.

Table 4.

Comparison of fiber diameter, pore size, porosity and WCA of unoptimized and optimized PVDF/PVDF-HFP ENM

Sample	Fiber diameter (nm)	Pore size (nm)	Porosity (%)	WCA (°)
Unoptimized PVDF/PVDF-HFP ENM	1029 ± 300	1766 ± 175	68.3 ± 3.1	107.7 ± 2.1
Optimized PVDF/PVDF-HFP ENM	750 ± 176	1410 ± 103	77.7 ± 3.2	130.3 ± 1.2

ENM: electrospun nanofibrous membrane; PVDF: polyvinylidene fluoride; PVDF-HFP: polyvinylidene fluoride hexafluoropropylene; WCA: water contact angle.

So far, many different types of ENMs have been fabricated for modifying its waterproof and moisture permeable properties. To evaluate the waterproof and moisture permeable properties of optimized PVDF/PVDF-HFP ENM, a comparison of WCA, hydrostatic pressure and moisture permeability of ENMs in this work with those in previous studies is shown in Table 5.^42–47 As can be seen, WCA values of ENMs were all over 100°, which was a prerequisite for the waterproof nature of ENMs. Compared with other ENMs, under the CCD of RSM, cross-electrospinning technology and hot-press method in this work could enhance PVDF/PVDF-HFP ENM with the higher hydrostatic pressure and moisture permeability. It would be an effective and simple way to fabricate waterproof and moisture permeable ENM, which could broaden its application in our daily products.

Table 5.

Comparison of WCA, hydrostatic pressure and moisture permeability of ENMs in the literature and this work

Sample	WCA (°)	Hydrostatic pressure (mmH₂O)	Moisture permeability (g · m⁻² · d⁻¹)	Reference
F-SiO₂/PU ENM	135	5102	10,400	42
SIPU/SA ENM	133	8928	8000	43
TPU/TBAC ENM	102.5	10,000	2170	44
PU/SiO₂ ENM	154	818	10,120	45
Amino-silicone PAN ENM	156	7581	11,400	46
PVDF/F-TiO₂/UV9 ENM	141.9	6142	10,600	47
Optimized PVDF/PVDF-HFP ENM	130.3	8460	11,130	This work

ENM: electrospun nanofibrous membrane; PU: polyurethane; PVDF: polyvinylidene fluoride; PVDF-HFP: polyvinylidene fluoride hexafluoropropylene; TPU: termoplastic polyurethane; WCA: water contact angle.

Waterproof and moisture permeability of composite fabrics

Tmhe results of waterproof and moisture permeability of three CFs bonded by different adhesives are shown in Figure 8. In Figure 8(a), CF-3 had the highest hydrostatic pressure value of 9840 mmH₂O. As a result of the scraper scraping method, a large number of adhesives entered the micropores inside ENM, resulting in a decrease in porosity and an increase in the hydrostatic pressure value.⁴⁸ The hydrostatic pressure of CF-2 increased for forming a layer of dense interface after the melt of hot-melt net. There was not a significant increase in hydrostatic pressure of CF-1, due to the point-bonding adhesive, which reduced the blockage on the micropores of ENM. As shown in Figure 8(b), CF-1 had the highest moisture permeability value of 10,280 g · m⁻² · d⁻¹. The smaller the porosity caused by hot-press process, the better the moisture permeability of the composite fabric. Due to the point-bonding adhesive in CF-1, which reduced the blockage on the micropores of ENM, resulting in the larger moisture permeability. As known in the art, most common products in the waterproof and breathable market only have hydrohead and moisture permeability as low as 2000 mmH₂O and 2000 g · m⁻² · d⁻¹, respectively. Some coated composite fabrics had the hydrohead value of 4571 mmH₂O and moisture permeability of 1506 g · m⁻² · d⁻¹, which were reported in the literature.^49,50 Only a few brand products such as Gore-Tex could achieve excellent hydrohead and moisture permeability as high as 10,000 mmH₂O and 10,000 g · m⁻² · d⁻¹, repectively.⁵ Therefore, it could be concluded that the tested results from our composite samples were comparable with Gore-Tex, showing great potential for practical application.

Figure 8.

Waterproof performance (a) and moisture permeability and (b) of composite fabrics.

Mechanical strength of composite fabrics

The tensile strength of ENM before and after hot-press process and the three CFs are shown in Figure 9(a) and (b). As can be seen from Figure 9(b), the tensile strength of the ENM before hot-press process (ENM-B) was 4.85 MPa, and that of the ENM after hot-press process (ENM-A) was 20.36 MPa. The tensile tenacity of the ENM after hot-press process had been significantly increased, due to the well bonding function for low melting-point PVDF-HFP ENM, thus improving the strength of the ENM. From Figure 9(a) and (b), it could also be seen that the tensile strength of the composite fabric was significantly higher than that of the ENM, and there was little difference in tensile strength of the three kinds of composite fabrics, because the strength of the composite fabric mainly came from the PET fabric. However, due to the different adhesives for CF-1, CF-2 and CF-3, their failure mechanism was also different. From Figure 9(a), CF-1 had the highest tensile force, tensile strength and higher break elongation, indicating that the mechanical properties of CF-1 were much better. As the adhesives of CF-1 and CF-3 were copolyamide, their tensile modulus was similar but larger than that of CF-2. Furthermore, CF-1 and CF-3 would rapidly fracture along a straight line when the highest force was reached, as shown in Figure 9(d)–(f). From the SEM results of Figure 9(d)–(f), almost all the fibers of CF-1and CF-3 were pulled out and broken directly and neatly, while the fibers of CF-2 were unevenly stretched and thinned.

Figure 9.

(a) The curves of force versus displacement of composite fabrics during tensile test; (b) tensile strength of electrospun nanofibrous membrane (ENM) before and after hot-press and composite fabrics; (c) peel strength of composite fabrics; (d) the optical photo and scanning electron microscope (SEM) result of CF-1 after tensile test; (e) the optical photo and SEM result of CF-2 after tensile test and (f) the optical photo and SEM result of CF-3 after tensile test.

The peel strength of the three CFs is shown in Figure 9(c). As can be seen from Figure 9(c), the peel strength of CF-3 was the highest value of 0.81 N · mm⁻¹. Because the water-soluble polyurethane adhesive in CF-3 was easy to penetrate the microporous membrane, and the contact area between the adhesive and the microporous membrane was huge, the bonding strength of adhesive was strong, resulting in the highest peel strength.⁵¹ CF-1 had relatively high peel strength of 0.78 N · mm⁻¹, as a result of the reactive polyurethane adhesive with good wettability for fluorine materials in CF-1. The copolyamide adhesive in CF-2 had the worst penetrating effect because it was difficult for the adhesive to enter the microporous membrane to form the bonding layer, resulting in the worst peeling strength.

Conclusions

In summary, optimized PVDF/PVDF-HFP ENM by CCD and composite fabric were prepared by cross-electrospining technology and hot-press method. The influence of four factors on the waterproof and moisture permeability of ENM was recorded and analyzed, thus in determining the optimized PVDF/PVDF-HFP ENM. The results show that the optimal conditions for the preparation of ENM were as follows: mass ratio of 2.96, temperature of 139°C, pressure of 0.57 MPa and time of 7.25 min. The experimental results of fiber diameter, pore size distribution and porosity also verified the reason for the excellent waterproof and moisture permeability of the optimized PVDF/PVDF-HFP ENM. Waterproof, moisture-permeability and peel strength of composite fabric with adhesives and optimal ENM were further studied. The CF-1 with reactive polyurethane adhesive had the best performance, with hydrostatic pressure of 9060 mmH₂O, moisture permeability of 10,280 g · m⁻² · d⁻¹, tensile strength of 150.79 MPa and peel strength of 0.78 N · mm⁻¹. Therefore, we believe that PVDF/PVDF-HFP ENM combined with electrospinning technology and hot-press process could be convenient to develop waterproof and moisture permeable fabrics.

Supplemental Material

sj-pdf-1-trj-10.1177_00405175221144086 - Supplemental material for Cross-electrospun PVDF/PVDF-HFP nanofibrous membrane with central combination design and its waterproof and moisture permeable composite fabric

Supplemental material, sj-pdf-1-trj-10.1177_00405175221144086 for Cross-electrospun PVDF/PVDF-HFP nanofibrous membrane with central combination design and its waterproof and moisture permeable composite fabric by Yanbo Liu, Xinyu Zhu, Yunxia Chen, Cong Zhou, Zhijun Chen, Ming Hao, Xiaodong Hu and Bo Yang in Textile Research Journal

Footnotes

Acknowledgements

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the National Natural Science Foundation of China (NSFC; no. 51973168) and the “Wuhan Talents Plan”-Hubei Wuhan's High level Talents Special Support Plan (no. [2022]734).

Author contributions

Yanbo Liu: investigation, methodology, supervision, data curation, writing review and editing. Xinyu Zhu: investigation, methodology, data curation, writing review and editing. Yunxia Chen: investigation, methodology, data curation, writing original draft, writing-review and editing. Cong Zhou: investigation, methodology, data curation. Zhijun Chen: resources, writing review and editing. Ming Hao: methodology, data curation. Xiaodong Hu: investigation, methodology, data curation. Bo Yang: conceptualization, resources, supervision, writing review and editing. All authors contributed to writing the manuscript. All authors have given approval to the final version of the manuscript.

Declaration of conflicting interests

The author(s) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Funding

ORCID iD

Bo Yang

Supplemental material

Supplemental material for this article is available online.

References

Kim

Park

Evaluation of the moisture transfer property of waterproof breathable fabric under low-temperature conditions depending on the pore size and distribution. Clothing Texts Res J 2018; 36: 310–323. DOI: https://doi.org/10.1177/0887302X18783089

Xin

Waterproof and moisture permeable nanofibrous membranes with cross-linked structure. J Phys: Conf Series 2021; 1790: 012069 (012067 pp). DOI: https://doi.org/10.1088/1742-6596/1790/1/012069

Painter

CJ.

Waterproof, breathable fabric laminates: a perspective from film to market place. J Ind Text 1996; 26: 107–130. DOI: https://doi.org/10.1177/152808379602600202

Sen

AK.

Coated Textiles: Principles and Applications, 2nd Ed. CRC Press, 2007. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742.

Gore

RW.

Process for producing filled porous PTFE products. Patent US05/637219, 1978.

Yue

Gong

Jiao

, et al. In-situ electrospinning of thymol-loaded polyurethane fibrous membranes for waterproof, breathable, and antibacterial wound dressing application. J Colloid Interf Sci 2021; 592: 310–318. DOI: https://doi.org/10.1016/j.jcis.2021.02.048

Tehrani-Bagha

AR.

Waterproof breathable layers – a review. Adv Colloid Interf Sci 2019; 268: 114–135. DOI: https://doi.org/10.1016/j.cis.2019.03.006.

Jml

Jmc

, et al. PCO-LLDPE thermoresponsive shape memory blends. Towards a new generation of breathable and waterproof smart membranes. Eur Polym J 2019; 119: 469–476. DOI: https://doi.org/10.1016/j.eurpolymj.2019.08.013

Sheng

Wang

, et al. Thermal inter-fiber adhesion of the polyacrylonitrile/fluorinated polyurethane nanofibrous membranes with enhanced waterproof-breathable performance. Separat Purif Technol 2016; 158: 53–61. DOI: https://doi.org/10.1016/j.seppur.2015.11.046

10.

Raghavan

Lim

Ahn

, et al. Electrospun polymer nanofibers: the booming cutting edge technology. React Funct Polym 2012; 72: 915–930. DOI: https://doi.org/10.1016/j.reactfunctpolym.2012.08.018

11.

Bhardwaj

Kundu

SC.

Electrospinning: a fascinating fiber fabrication technique. Biotechnol Adv 2010; 28: 325–347. DOI: https://doi.org/10.1016/j.biotechadv.2010.01.004

12.

Cao

, et al. Robust hydrophobic polyurethane fibrous membranes with tunable porous structure for waterproof and breathable application. Appl Surf Sci 2018; 439: 589–597. DOI: https://doi.org/10.1016/j.apsusc.2017.12.267

13.

Kadam

Wang

Padhye

Electrospun nanofibre materials to filter air pollutants – a review. J Ind Text 2018; 47: 2253–2280. DOI: https://doi.org/10.1177/1528083716676812

14.

Liu

Huang

Liao

, et al. Treatment of CrVI-containing Mg(OH)² nanowaste. Angewandte Chemie Int Ed 2008; 47: 5619–5622. https://doi.org/10.1002/anie.200800172. DOI: https://doi.org/10.1002/anie.200800172

15.

Zhang

Wang

Zhang

, et al. The performance of electrode ultrafiltration membrane bioreactor in treating cosmetics wastewater and its anti-fouling properties. Environment Res 2022; 206: 112629. DOI: https://doi.org/10.1016/j.envres.2021.112629

16.

Sahay

Kumar

Sridhar

, et al. Electrospun composite nanofibers and their multifaceted applications. J Mater Chem 2012; 22: 12953–12971. 10.1039/C2JM30966A. DOI: https://doi.org/10.1039/C2JM30966A

17.

Sell

Wolfe

Garg

, et al. The use of natural polymers in tissue engineering: a focus on electrospun extracellular matrix analogues. Polymers 2010; 2: 522–553. DOI: https://doi.org/10.3390/polym2040522

18.

Tian

Ren

Zhang

, et al. Preparation of fluorine-free waterproof and breathable electrospun nanofibrous membranes via thiol-ene click reaction. Macromol Mater Engng 2022; 307: 2100757. DOI: https://doi.org/10.1002/mame.202100757

19.

Banuskeviciute

Adomaviciute

Milasius

Investigation of water permeability of thermoplastic polyurethane (TPU) electrospun porous mat. Mater Sci 2013; 19: 178–183. Article. DOI: https://doi.org/10.5755/j01.ms.19.2.4435

20.

Feng

Chen

, et al. Environmentally friendly, durably waterproof, and highly breathable fibrous fabrics prepared by one-step fluorine-free waterborne coating. ACS Appl Mater Interf 2022; 14: 8613–8622. DOI: https://doi.org/10.1021/acsami.1c23664

21.

, et al. Amphiphobic fluorinated polyurethane composite microfibrous membranes with robust waterproof and breathable performances. RSC Adv 2013; 3: 2248–2255. Article. DOI: https://doi.org/10.1039/c2ra22111j

22.

, et al. Waterproof and breathable electrospun nanofibrous membranes. Macromol Rapid Commun 2019; 40: 1800931. DOI: https://doi.org/10.1002/marc.201800931

23.

Zhao

Zhu

Yan

, et al. Tailoring waterproof and breathable properties of environmentally friendly electrospun fibrous membranes by optimizing porous structure and surface wettability. Composit Commun 2019; 15: 40–45. Article. DOI: https://doi.org/10.1016/j.coco.2019.06.002

24.

Wang

, et al. A waterproof and breathable nanofibrous membrane with thermal-regulated property for multifunctional textile application. J Appl Polym Sci 2021; 138: 50391. Article. DOI: https://doi.org/10.1002/app.50391

25.

Luo

Zhang

, et al. A flexible electrostatic nanogenerator and self-powered capacitive sensor based on electrospun polystyrene mats and graphene oxide films. Nanotechnology 2021; 32: 405402. DOI: 10.1088/1361-6528/ac1019

26.

Zhu

, et al. Directly printed embedded metal mesh for flexible transparent electrode via liquid substrate electric-field-driven jet. Adv Sci 2022; 9: 2105331. https://doi.org/10.1002/advs.202105331. DOI: https://doi.org/10.1002/advs.202105331

27.

Zhang

Tai

, et al. Flexible transparent electromagnetic interference shielding films with silver mesh fabricated using electric-field-driven microscale 3D printing. Optics Laser Technol 2022; 148: 107717. DOI: https://doi.org/10.1016/j.optlastec.2021.107717

28.

Zhou

Sun

Jiang

, et al. Flexible and conductive meta-aramid fiber paper with high thermal and chemical stability for electromagnetic interference shielding. Appl Surf Sci 2020; 533: 147431. DOI: https://doi.org/10.1016/j.apsusc.2020.147431

29.

Akbari

Lashanizadegan

Darvishi

, et al. Preparation of hydrophobic flat sheet membranes from PVDF-HFP copolymer for enhancing the oxygen permeance in nitrogen/oxygen gas mixture. Chin J Chem Engng 2020; 28: 1566–1581. DOI: https://doi.org/10.1016/j.cjche.2020.02.018

30.

Chen

Liu

, et al. Improved performance of PVdF-HFP/PI nanofiber membrane for lithium ion battery separator prepared by a bicomponent cross-electrospinning method. Mater Lett 2014; 133: 67–70. Article. DOI: https://doi.org/10.1016/j.matlet.2014.06.163

31.

Zhang

Sheng

Yin

, et al. Polyvinyl butyral modified polyvinylidene fluoride breathable–waterproof nanofibrous membranes with enhanced mechanical performance. Macromol Mater Engng 2017; 302: 1600272. DOI: https://doi.org/10.1002/mame.201600272

32.

Zhao

Wang

, et al. Preparation and characterization of superhydrophobic PVDF/HMSNs hybrid membrane for CO₂ absorption. Polymer 2020; 214: 123242. DOI: https://doi.org/10.1016/j.polymer.2020.123242

33.

Jiao

Yan

Wang

, et al. Low surface energy nanofibrous membrane for enhanced wetting resistance in membrane distillation process. Desalination 2020; 476: 114210. DOI: https://doi.org/10.1016/j.desal.2019.114210

34.

Momenzadeh

Miyanaji

Berfield

TA.

Influences of zirconium tungstate additives on characteristics of polyvinylidene fluoride (PVDF) components fabricated via material extrusion additive manufacturing process. Int J Adv Manuf Technol 2019; 103: 4713–4720. DOI: https://doi.org/10.1007/s00170-019-03978-7

35.

Mansouri

Chen

Silica nanoparticles as carriers of antifouling ligands for PVDF ultrafiltration membranes. J Membr Sci 2013; 433: 135–151. DOI: https://doi.org/10.1016/j.memsci.2013.01.029

36.

Gugliuzza

Drioli

PVDF and HYFLON AD membranes: ideal interfaces for contactor applications. J Membr Sci 2007; 300: 51–62. DOI: https://doi.org/10.1016/j.memsci.2007.05.004

37.

Xiao

Han

Shi

Optimization of microwave‐assisted extraction of flavonoid from radix astragali using response surface methodology. Separat Sci Technol 2008; 43: 671–681. DOI: https://doi.org/10.1080/01496390701812509

38.

Wenzhu

Zhipeng

, et al. Optimized extraction of polysaccharides from corn silk by pulsed electric field and response surface quadratic design. J Sci Food 2011; 91: 2201–2209. DOI: https://doi.org/10.1002/jsfa.4440

39.

Maxwell

Mary

Ghate

, et al. A Novel high throughput 96-well based fluorimetric method to measure amikacin in pharmaceutical formulations: development using response surface methodology. Luminescence: the journal of biological and chemical luminescence 2022; 37: 930 Journal Article. DOI: https://doi.org/10.1002/bio.4238

40.

Karun

Sukumar

Nagamaniammai

, et al. Development of multigrain ready-to-eat extruded snack and process parameter optimization using response surface methodology. J Food Sci Technol 2022; 1–11. Article. DOI: https://doi.org/10.1007/s13197-022-05390-8

41.

Javid

Nasseri

Mesdaghinia

, et al. Performance of photocatalytic oxidation of tetracycline in aqueous solution by TiO2 nanofibers. J Environment Health Sci Engng 2013; 11: 24. Article. DOI: https://doi.org/10.1186/2052-336X-11-24

42.

Liu

Zhang

, et al. Preparation of waterproof and breathable polyurethane fiber membrane modified by fluorosilane-modified silica. Fibers Polym 2020; 21: 954–964. DOI: 10.1007/s12221-020-9562-z

43.

Zhang

Ren

Tian

, et al. Environmentally friendly waterproof and breathable nanofiber membranes with thermal regulation performance by one-step electrospinning. Fibers Polym 2022; 23: 2139–2148. DOI: 10.1007/s12221-022-4146-8

44.

Shi

Deng

, et al. Designing waterproof breathable material with moisture unidirectional transport characteristics based on a TPU/TBAC tree-like and TPU nanofiber double-layer membrane fabricated by electrospinning. RSC Adv 2017; 7: 32155–32163. DOI: 10.1039/c7ra04843b

45.

Wang

Chen

, et al. Durable polyurethane/SiO₂ nanofibrous membranes by electrospinning for waterproof and breathable textiles. ACS Appl Nano Mater 2022; 5: 10686–10695. DOI: 10.1021/acsanm.2c02017

46.

Sheng

, et al. Robust fluorine-free superhydrophobic amino-silicone oil/SiO₂ modification of electrospun polyacrylonitrile membranes for waterproof-breathable application. ACS Appl Mater Interf 2017; 9: 15139–15147. DOI: 10.1021/acsami.7b02594

47.

Liu

Deng

Zhang

, et al. Facile fabrication of environmentally friendly, waterproof, and breathable nanofibrous membranes with high UV-resistant performance by one-step electrospinning. Ind Engng Chem Res 2020; 59: 4447–4458. DOI: 10.1021/acs.iecr.9b05617

48.

Lin

Bian

, et al. Improving waterproof/breathable performance of electrospun poly(vinylidene fluoride) fibrous membranes by thermo-pressing. J Polym Sci Part B: Polym Phys 2018; 56: 36–45. DOI: https://doi.org/10.1002/polb.24534

49.

Chen

, et al. Intumescent flame-retardant and self-healing superhydrophobic coatings on cotton fabric. ACS Nano 2015; 9: 4070–4076. DOI: 10.1021/acsnano.5b00121

50.

Bramhecha

Sheikh

Development of sustainable citric acid-based polyol to synthesize waterborne polyurethane for antibacterial and breathable waterproof coating of cotton fabric. Ind Engng Chem Res 2019; 58: 21252–21261. DOI: 10.1021/acs.iecr.9b05195

51.

Lalia

Guillen-Burrieza

Arafat

, et al. Fabrication and characterization of polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) electrospun membranes for direct contact membrane distillation. Jf Membr Sci 2013; 428: 104–115. DOI: https://doi.org/10.1016/j.memsci.2012.10.061

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.15 MB