coatings

Article
Water Repellency/Proof/Vapor Permeability Characteristics of
Coated and Laminated Breathable Fabrics for Outdoor Clothing
Hyun-Ah Kim
Korea Research Institute for Fashion Industry, Daegu 41028, Korea; ktufl@krifi.re.kr

Abstract: This study examined the water repellency (WR), waterproof, and water vapor permeability
(WVP) characteristics of twelve types of laminated and coated woven fabrics for outdoor clothing.
These characteristics were compared with the fabric structural parameters, such as cover factor,
thickness, and weight, and surface modification (finishing) factors, such as coating, laminating,
and Teflon treatments. In addition, an eco-friendly process for surface modification was proposed
followed by a summary. Superior waterproof-breathable characteristics with 100% water-repellency
were achieved in specimen 3 in group A by treatment with a hydrophilic laminated finish using
nylon woven fabric with a cover factor between 0.7 and 0.9 in a 2.5-layered fabric, which was the best
specimen with waterproof-breathable characteristics. A high WVP in the coated and laminated fabrics
was observed in the fabrics with a low weave density coefficient (WDC) and low thickness per unit
weight of the fabric, whereas superior water repellency and waterproof characteristics were observed
in the high-cover-factor (WDC) fabric with appropriate fabric thickness. The determination coefficient
(R2 ) from regression analysis between the WVP and fabric structural parameters indicated a higher
contribution of the fabric structural parameters than surface modification factors, such as coating and
laminating to the WVP in the coated and laminated fabrics. Furthermore, the cover factor was the
most important factor influencing the WVP of the waterproof-breathable fabrics. Of twelve coated





 and laminated fabrics, the laminated nylon and nylon/cotton composite fabrics showed superior
Citation: Kim, H.-A. Water WVP with high WR and waterproof characteristics. Accordingly, based on the WR, waterproof, and
Repellency/Proof/Vapor WVP characteristics of the coated and laminated breathable fabrics, the laminating method, as an
Permeability Characteristics of eco-friendly process, is recommended to obtain better waterproof-breathable fabrics.
Coated and Laminated Breathable
Fabrics for Outdoor Clothing. Keywords: water vapor permeability; waterproof characteristics; coated and laminated fabrics;
Coatings 2022, 12, 12. https:// weave density coefficient; Teflon-finished; backward regression
doi.org/10.3390/coatings12010012

Academic Editor:
Ioannis Karapanagiotis
1. Introduction
Received: 24 November 2021
Accepted: 15 December 2021
Consumers who are regularly involved in outdoor activities, such as sports and leisure,
Published: 23 December 2021
or subjected to extreme conditions (snow, rain, cold, and wind) require multifunctional
clothing [1], and the global market for waterproof-breathable textiles is growing annually.
Publisher’s Note: MDPI stays neutral
Such clothing should keep the wearer dry and comfortable under cold, hot, and wet
with regard to jurisdictional claims in
conditions. To achieve this, the fabric and clothing need to be waterproof and water-
published maps and institutional affil-
vapor-permeable [1]. Therefore, waterproofing and water-vapor-permeable (breathable)
iations.
fabrics are used and marketed by various outdoor clothing companies with worldwide
brands. The basic characteristics of water vapor permeability and waterproofing (WP),
including water repellency (WR) for the famous outdoor clothing, are well known through
Copyright: © 2021 by the author.
the introduction by famous outdoor companies. Although waterproofing and breathability
Licensee MDPI, Basel, Switzerland. are commonly combined and used to imply both concepts, they are entirely different.
This article is an open access article Breathability is defined as the ability of a fabric to allow perspiration from the human
distributed under the terms and body to evaporate and diffuse to the outside [2,3]. Waterproofness is an extreme case of
conditions of the Creative Commons water resistance, implying complete resistance to water [4,5]. Water repellency generally
Attribution (CC BY) license (https:// refers to the ability of a fabric to resist wetting [6]. The physical properties related to the
creativecommons.org/licenses/by/ breathable characteristics of outdoor fabrics are water repellency, hydrostatic pressure (HP)
4.0/). for waterproofing, and water vapor permeability (WVP), which are used in the commercial

Coatings 2022, 12, 12. https://doi.org/10.3390/coatings12010012 https://www.mdpi.com/journal/coatings

Coatings 2022, 12, 12 2 of 13

trade between clothing brand companies and fabric manufacturers. In addition, these
experimental items are used in the protective clothing area, such as firefighter’s clothing,
military combat clothing, and clothing against cold and inclement weather.
Some studies [7–9] on the waterproof, water-repellent, and breathable characteristics
of the coated and laminated fabrics for sports and protective clothing have been performed.
The materials used in these protective clothing are called WWWW textiles because they
are waterproof, water-vapor-permeable, windproof, and water-repellent. These modern
materials have attempted to solve the perennial problem of keeping active humans dry
while allowing perspiration vapor to escape freely [7]. WWWW materials can be classi-
fied into three main types. The first includes high-density woven fabrics called Ventile®
treated with a Velan PF® finish. Modern analogs are based on tightly woven microfiber
polyester fabrics treated with silicone or fluorocarbon repellent finishes [8]. The second
contains microporous coatings and membranes, including Gore-Tex® based on microp-
orous PTFE membranes with pore sizes between 0.1 and 5 µm, and is highly hydrophobic.
Aquatex® is another microporous coating and membrane based on polyurethane chem-
istry [8]. The third is hydrophilic solid coatings and films, including Sympatex® based
upon a modified polyester film [9]. Therefore, the fundamental physical properties of
WWWW materials used in protective clothing are water-repellency, waterproofness, and
water vapor permeability.
Some studies [10–13] have examined the four W characteristics of cotton, wool,
PET, and nylon textile materials, and their characteristics according to the textile ma-
terials and various experimental methods for the four W characteristics. Of these studies,
Cubric et al. [13] examined the impact of fibers, yarn, and knitted fabric structural parame-
ters, as well as the finishing of the fabric and body activity on the water vapor resistance
measured using a sweating-guarded hot plate and thermal manikin. They reported that
the correlation coefficient between water vapor resistance and moisture regain was 0.7, and
the prominent structural factors of knitted fabric affecting water vapor resistance were the
mass per unit area, fabric thickness, and tightness factor. Yoo and Kim [14,15] explored
the effect of a layer array method in a multilayer clothing system on the vapor permeabil-
ity and condensation, which was made using a simulator assessment. Gorjanc et al. [16]
used thermal conductivity and water cup methods to examine the influence of elastane
(Spandex) and fabric structural parameters (fabric density and weave pattern) on the ther-
mal and water vapor resistance. They reported that elastane-incorporated cotton fabric
with a twill weave has a higher thermal and water vapor resistance than conventional
cotton fabric. Lee and Obendorf [17] examined the effects of the fiber materials and fabric
structural parameters affecting the water vapor transport of fifteen woven fabrics using an
upright cup measuring method. They reported that the fabric thickness, cover factor, void
diameter, and absorption of constituent fiber were significant factors affecting the water
vapor transport. Rego et al. [18] investigated the wear comfort of the elastane-incorporated
cotton/polyester fabrics using a sweating-guarded hot plate method. They reported the
effect of the fabric thickness and air permeability on the water vapor resistance. Many
studies explored previously related to the water vapor resistance of knitted and woven
fabrics have been performed using staple yarns made from cotton, polyester, and wool, as
well as their blended materials.
On the other hand, Ruckmann compared the performance of different waterproof-
breathable fabrics composed of nylon and PET synthetic fibers [19–21]. In addition, Ruck-
mann and Murray [22] examined heat loss in the external layer using zippers and openings
of clothing for improved thermo-physiological comfort. In particular, Ren and Ruck-
man [23,24] investigated the water vapor permeability and condensation in cold weather
clothing. They [24] suggested a method of reducing condensation on waterproof-breathable
fabric by changing its hydrophilicity. Recently, Kim [25] examined the WVP and moisture
vapor resistance of 73 waterproof-breathable fabrics classified according to fiber materials
(nylon and PET) and five types of surface modification methods (laminated, coated, dot
laminated, hot melt laminated, and Teflon-finished). The experimental data measured using
Coatings 2022, 12, 12 3 of 13

different measuring methods were compared in terms of the fiber materials, the fabric struc-
tural parameters, and the surface modification method. In addition, Scott [26] compared
the relative performance of WWWW materials related to WVP and waterproof character-
istics according to the laminating and coating methods. Several researchers [27–29] have
compared the performance of WVP of different types of waterproof-breathable fabrics.
However, few studies have examined the waterproof, windproof, breathable (WWB),
and four W characteristics of outdoor shell fabrics. Moreover, few studies have made
an in-depth comparison between the breathable characteristics including the WR and
waterproofing of laminated and coated fabrics and fabric structural parameters made of
nylon and PET, including surface modification (finishing) treatment such as laminating and
coating. On the other hand, the environmental impact of human beings has taken various
forms, which includes pollution and energy consumption, together with global warming,
rising sea levels, and the increasing frequency of adverse weather conditions [30]. Albeit
a minor contributor, the textile industry is exerting some impact, and the contribution of
environmental concerns in chemical processing has to be taken into account with effluents in
dyehouses and the coating process. Of the surface modification methods for the waterproof-
breathable fabrics, the polyurethane (PU) coating method is a kind of pollution-developing
process, not an eco-friendly technology. Hence, the PU coating method is gradually
being substituted with the laminating method. Many technologists in the coating and
laminating manufacturers want to have information related to the differences in WR,
waterproof, and WVP characteristics of different types of breathable fabrics finished with
PU coating, laminating, and Teflon treatments, even though these characteristics were
separately studied and published.
Therefore, the aim of this research was to examine the differences in the WR, water-
proof, and WVP characteristics between coated and laminated fabrics, and an eco-friendly
process for surface modification was proposed. Accordingly, in this study, twelve types of
waterproof, water-repellent, and breathable fabrics were prepared, and the water-repellency
(WR), hydrostatic pressure (HP), and water vapor permeability (WVP) of these fabrics were
measured and compared in terms of fabric structural parameters and surface modification
factors. Finally, an environmentally friendly process for surface modification was proposed
to obtain better waterproof-breathable fabrics.

2. Materials and Methods

2.1. Fabric Specimens
Various types of waterproof-breathable fabric specimens, which are commercialized in
the outdoor market, supplied from the coating and laminating manufacturers were used in
this experiment. Twelve coated and laminated woven fabrics for outdoor clothing were pre-
pared and classified into four groups: group A (Inno-tex, Shinpung Textiles, Daegu, Korea),
nylon 6 waterproof-breathable fabrics (3 specimens), which are composed of nylon fabric
materials coated with hydrophilic-type polyurethane (PU) (specimen 2), and laminated
with hydrophilic-type PU (specimens 1 and 3). In particular, specimen 3 was composed
of nylon fabric laminated with hydrophilic-type PU with knitted tricot at the back of the
fabric (next to skin), which is called a 2.5-layered fabric; group B (Zemintex, Wonchang
Materials, Daegu, Korea), PET microfiber high-density breathable fabrics (2 specimens) and
PET-laminated breathable fabrics (2 specimens), which are composed of polyester fabrics
laminated with a thin breathable film (specimens 4 and 5), and high-density PET fabrics
with microfibers (specimens 6 and 7); group C (Northface, Youngone, Daegu, Korea), nylon
66 Teflon/coated breathable fabrics (3 specimens), which are composed of high-density ny-
lon 66 fabric finished with Teflon (specimen 8), and nylon 66 hydrophilic and microporous
PU-coated fabrics (specimens 9 and 10); group D (Monotex, Shinhung, Daegu, Korea),
nylon/cotton-laminated breathable fabrics (2 specimens), which consist of nylon/cotton
blend fabrics laminated with thin breathable films (specimens 11 and 12). Table 1 lists the
characteristics of twelve fabric specimens. The yarn linear density and fabric density of the
Coatings 2022, 12, 12 4 of 13

fabric specimens were measured using the experimental methods of JIS L 1096 [31]. The
fabric thickness and weight were measured using JIS L 1096 [31].

Table 1. Specimens according to materials and surface modification method.

Yarn Number (d) Fabric Density

Specimen
Wp Wf Material Characteristics Remark
No. Wp Wf
(ends/in) (picks/in)
Nylon hydrophilic
1 80 83 232 120 2 layer
PU-laminated fabric
Nylon hydrophilic
Group A 2 56 71 170 93 2 layer
PU-coated fabric
Nylon hydrophilic
3 84 108 85 85 PU-laminated and 2.5 layer
tricot-layered fabric
Polyester hydrophilic-
4 131 121 95 140 2 layer
laminated fabric
5 68 164 233 100 Polyester-coated fabric 2 layer
Group B Polyester microfiber
6 56 65 212 130 1 layer
high-density fabric
Polyester microfiber
7 53 54 158 72 1 layer
high-density fabric
Nylon-66 Teflon finished
8 92 183 160 68 and microfiber 1 layer
high-density fabric
Group C Nylon-66 hydrophilic
9 177 80 165 124 2 layer
PU-coated fabric
Nylon-66 microporous
10 89 178 152 70 2 layer
PU-coated fabric
Nylon/cotton-
11 41 272 118 83 2 layer
laminated fabric
Group D
Nylon/cotton-
12 64 67 120 108 2 layer
laminated fabric
Note: Wp: warp, Wf: weft.

2.2. Measurement of the Physical Properties of the Fabric Specimens

2.2.1. Water Repellency
The water repellency of the fabric specimens was measured using the spray method [32].
As shown in Figure 1a, a fabric specimen of 20 cm × 20 cm was laid on a 45◦ -inclined
plate, and 250 mL of 20 °C water in a triangle flash was sprayed on the fabric specimen for
25–30 s. The wetted fabric specimen was compared with replicas (standard samples), and
the water repellency (%) was assessed as a percentage.

2.2.2. Waterproof by Hydrostatic Pressure Test

The level of waterproofing by hydrostatic pressure (HP) was measured using the JIS L
1092 method [32], as shown in Figure 1b. A 15 cm × 15 cm fabric specimen was prepared
and clamped on the hydrostatic pressure apparatus (FX3000, Textest AG, Schwerzenbach,
Switzerland). The water level (mm) in the manometer of a water bath was taken as the
hydrostatic pressure of water leaking from the three positions on the fabric specimen
clamped on the apparatus at 20 ◦ C in a water bath was filled at a speed of 60 ± 3 cm/min.
Coatings 2022, 12, 12 5 of 13

Figure 1. Schematic diagram of the water and vapor permeability measuring apparatus. (a) water
repellency apparatus, Gelanots, Osaka, Japan (JIS L 1092), (b) hydrostatic apparatus, Textest AG,
Schwerzenbach, Switzerland (JIS L 1092), and (c) WVP apparatus, Gelanots, Osaka, Japan (JIS L 1099).

2.2.3. Water Vapor Permeability

The water vapor permeability (WVP, g/m2 ·24 h) of the fabric specimen was measured
using the JIS L 1099 method [33]. The specimen, 8 cm in diameter, was prepared and
conditioned at 20 ± 1 ◦ C and R.H of 65 ± 5% for 24 h. A shallow impermeable and
breathable cup was prepared and filled with a desiccant agent (potassium acetate) as an
absorption material. Distilled water was placed in an assembly bath with a height of 42 mm
on which a breathable cup was laid, in which the temperature and R.H. were maintained
at 40 ± 2 ◦ C and 50 ± 5%, respectively. The water vapor was transmitted through the
fabric specimen from inside the assembly cup to the breathable cup surrounded by the
desiccating agent (potassium acetate). The increase in mass of the breathable cup after a
specific time has elapsed is equal to the mass of water vapor that passed through the fabric
specimen. The water vapor permeability was calculated using Equation (1):

WVP = 10 × 24(a1 − a2 )/S (1)

where WVP is water vapor permeability (g/m2 ·24h); a1 −a2 is the mass of the breathable
cup (mg) before and after the test for one hour, and S is the specimen area (cm2 ).
Coatings 2022, 12, 12 6 of 13

2.3. Fabric Structural Parameter

The weave density coefficient (WDC), as a measure of the cover factor, of the fabric
specimens was calculated using the yarn linear density and fabric density shown in Table 1,
using Equations (2)–(4) [34].
πD2
d = ρf × × 9 × 105 (2)
4
WDC 25.42
WD × FD = × (3)
WF (Dw + Df )2
R + Cr 2
 
WF = (4)
2R
where d is the denier; ρf is the fiber density; D is the yarn diameter (mm); Dw is the warp
yarn diameter (mm); Df is the weft yarn diameter (mm); WD × FD is the warp density
(ends/in) × filling density (picks/in); WDC is the weave density coefficient; WF is the
weave factor; R is the number of yarns in the one repeat weave; and Cr is the number of
interlacing points in the one repeat weave.

3. Results and Discussion

3.1. Water Repellency of Breathable Fabric Specimens
Some of the terms relevant to this study need to be defined. The water repellency (WR)
generally refers to the ability of a fabric to resist wetting [6]. Water-repellent fabrics provide
some protection against intermittent rain but are unsuitable in a downpour; water will
come through under sufficient pressure. The pressure required to do so is a measure of the
water-resistance [1]. Waterproofness measures the resistance of a fabric to the penetration
of water under hydrostatic pressure [6], which is called a hydrostatic pressure (HP) test.
Waterproofness is the extreme case of water resistance, implying complete resistance to
water. Therefore, in this study, the water repellency of waterproof-breathable fabrics
was measured using the spray test method, which determines the resistance to surface
wetting of fabrics. On the other hand, waterproofness was measured using the HP test
method as an extreme case of water resistance. Table 2 lists the physical properties of the
waterproof-breathable fabric specimens. ANOVA (F-test) was carried out to verify the
statistical significance of the experimental data shown in Table 2. The deviation in Table 2
stands for the difference between maximum and minimum values of five experimental data
points of each specimen. ANOVA was performed between the mean value of the HP and
WVP of each specimen with the 95% confidence limit (5% significance level). Table 3 lists
the ANOVA analysis of the HP and WVP of 12 fabric specimens. As shown in Table 3, the
significance test between each mean HP among 12 specimens was statistically significant,
as F0 (V/Ve) > F (11, 48, 0.95) and p < 0.05. Similarly, WVP was statistically significant, as
F0 (V/Ve) > F (11, 48, 0.95) and p < 0.05, as shown in Table 3.
As shown in Table 2, most specimens except for specimens 6 and 7 exhibited 100%
water repellency (WR), indicating that waterproof-breathable fabrics have water repellency,
i.e., laminated and coated treatments, to obtain the breathable property accompanying
water-repellent characteristics. In addition, the high-density fabric (1 layer) without lami-
nated and coated treatments (specimens 6 and 7) exhibited 90% water repellency. On the
other hand, the high-density fabric (specimen 8) treated with a Teflon WR finish showed
100% water repellency with a low HP and WVP, which was attributed to the Teflon WR fin-
ish albeit with a one-layer fabric. According to a prior study [1,26], waterproof-breathable
fabrics require a water-repellent property, and the main methods for imparting water
repellency to woven fabric textiles are mechanical, chemical, and coating treatments; of
these methods, the water-repellent property by the mechanical method can be achieved by
appropriate selection of the fabric structure and tightness, together with the appropriate
fiber, yarn composition, and properties. In addition, the 90% WR results of specimens 6
and 7 indicate a limit to the WR of high-density fabric as a mechanical method. On the
Coatings 2022, 12, 12 7 of 13

other hand, specimen 8 treated with a Teflon finish and other coated fabrics exhibited 100%
WR values.

Table 2. Specimens according to materials and surface modification method.

HP WVP
Surface WR Structure Cover Thickness Weight
Sample Materials (mmH2 O) (g/(m2 ·24 h))
No. Modification (%) (Layers) Factor (mm) (g/cm2 )
Method Mean Dev. Mean Dev. (WDC)
1 Nylon Laminated 100 8720.8 206.1 8336.8 260.1 2 1.23 0.189 0.0110
Group A 2 Nylon Coating 100 5689.4 165.3 8024.2 276.3 2 0.96 0.112 0.0096
3 Laminated with 100 11,200.5 267.2 12,017.2 393.4 2.5 0.66 0.321 0.0137
Nylon tricot
4 PET Laminated 100 9870.6 190.3 7542.5 178.1 2 1.60 0.256 0.0143
Group 5 PET Coating 100 5562.5 168.1 6217.8 179.3 2 1.09 0.291 0.0163
B 6 PET HD fabric 90 762.8 100.3 11,214.2 249.5 1 1.60 0.154 0.0091
7 PET HD fabric 90 325.5 84.1 12,013.2 232.4 1 1.58 0.117 0.0070

8 HD and 100 821.6 105.3 2513.6 89.3 1 2.44 0.315 0.0110

Nylon
Group Teflon-finished
C 9 Nylon H-PU Coating 100 2236.2 174.1 2212.5 80.1 2 1.33 0.346 0.0150
10 Nylon M-PU Coating 100 1518.8 126.3 12,112.4 285.2 2 0.73 0.370 0.0150

11 Nylon/ 100 6011.5 131.2 12,012.1 378.1 2 0.81 0.109 0.0081

Laminated
Group D Cotton
12 Nylon/ 100 10,820.5 379.1 8812.4 176.2 2 0.95 0.382 0.0225
Laminated
Cotton
Note: M-PU: microporous PU. HD: high-density. H-PU: hydrophilic PU.

Table 3. ANOVA analysis of the fabric physical properties.

Physical Properties F-Value (F0 ) F (11, 48, 0.95) p-Value

HP 15,617.86 1.99 2.56 × 10−81 (p < 0.05)
WVP 6410.45 1.99 4.84 × 10−72 (p < 0.05)

3.2. Waterproof Characteristics of Breathable Fabric Specimens

As mentioned previously, waterproofness is an extreme case of water resistance,
and waterproofness measures the resistance of a fabric to the penetration of water under
hydrostatic pressure. Accordingly, the HP test method was used to measure the waterproof
characteristics of the breathable fabric specimens. Figure 2 presents HP (mean) with
the deviation of twelve fabric specimens listed in Table 2. The mean value between
each specimen for the HP was statistically significant, as shown in Table 3. As shown in
Figure 2, hydrophilic PU-laminated nylon (specimen 1), hydrophilic PU-laminated nylon
(2.5 layers) with tricot (specimen 3), laminated PET (specimens 4), and nylon/cotton-
laminated (specimens 11 and 12) fabrics exhibited a higher HP than those of the PU-
coated fabrics (specimens 2, 5, 9, and 10). In particular, one-layer fabrics (specimens 6, 7,
and 8) showed low HP values below 1000 mmH2 O, even though they are high-density
fabrics, and specimen 8 treated with a Teflon finish showed 100% WR. Specimens 9 and 10
coated with PU by hydrophilic and microporous methods showed a low HP, even though
they are two-layer fabrics showing 100% WR. However, the hydrophilic PU-coated fabric
(specimen 9) showed a higher HP than the microporous PU-coated fabric (specimen 10),
which is consistent with the prior finding [28]. These results suggest that the laminating
method is pertinent to obtaining superior waterproof characteristics with a high HP above
6000 mmH2 O and superior to the coating method. This finding is in accordance with
the prior study performed by Scott [26]. He reported that the waterproof property of
laminated fabrics was superior to that of PU-coated fabrics, which compared the general
representative groups by market leader for highest performance for WWWW materials. On
the other hand, the waterproof fabrics showing an HP more than 6000 mmH2 O exhibited
superior water-repellency with 100% WR.
Coatings 2022, 12, 12 8 of 13

Figure 2. HP of twelve fabric specimens.

3.3. Water-Vapor-Permeable Characteristics of Breathable Fabric Specimens

Figure 3 presents the water vapor permeability (WVP) of the twelve fabric specimens.
The mean value between each specimen for the WVP was statistically significant, as shown
in Table 3. Specimens 1, 2, 3, 6, 7, 10, 11, and 12 showed a relatively high WVP above
8000 g/m2 ·24 h. Of these, fabric specimens 3, 6, 7, 10, and 11 showed a superior WVP above
10,000 g/m2 ·24 h. Specimens 6 and 7 are high-density PET fabrics with cover factors of 1.60
and 1.58, respectively. Specimens 2 and 10 are coated fabrics, and specimens 1, 11, and 12
are laminated fabrics. These results suggest that the manufacturing methods of breathable
fabrics used in this study are highly dense and tightly coated and laminated fabric methods
(or microporous and solid film types), which have been explained previously. Moreover,
high-density PET fabrics (specimens 6 and 7) showing superior WVP exhibited a low HP
and WR, which are consistent with those of a previous study [26], and the microporous
PU-coated nylon fabric (specimen 10) showed a low HP with superior WVP. Except for
these fabrics, the superior WVP fabrics exhibited a high HP and 100% WR. In particular,
the Teflon finish-treated and hydrophilic PU-coated fabrics (specimens 8 and 9) exhibited
an inferior WVP and low HP. Hence, inferior-WVP and -WR fabrics are accompanied by a
poor HP, whereas superior-WVP fabrics treated with coated and laminated finishes exhibit
good waterproofing and water repellency.
Coatings 2022, 12, 12 9 of 13

Figure 3. Water vapor permeability of 12 fabric specimens.

An examination of the WVP of four groups of specimens showed that in group A,

tricot-incorporated 2.5-layer-laminated nylon fabric (specimen 3) exhibited an excellent
WVP with a high HP and 100% WR compared to the other laminated two-layer nylon
fabrics (specimens 1 and 2). This highlights the importance of layers in breathable fabrics.
However, even superior waterproof and breathable characteristics of 2.5-layer-laminated
fabric to 2 layer ones, comfort and aesthetic qualities, such as tactile hand, drape, and visual
appearance, are limited. In group B with PET breathable fabrics, the WVP of the high-
density PET fabrics (specimens 6 and 7) was much higher than that of the laminated and
coated PET fabrics (specimens 4 and 5), but they exhibited a low HP and WR, which is not
pertinent to waterproof-breathable fabrics, highlighting the importance of the laminated
and coated finishes of the waterproof-breathable fabric. Group C was classified with three
types of nylon fabrics: high-density nylon fabric with a Teflon finish (specimen 8), high-
density hydrophilic PU-coated nylon fabric (specimen 9), and low-density microporous
PU-coated nylon fabric (specimen 10). The WVP of the microporous PU-coated nylon
fabric (specimen 10) was much higher than those of the hydrophilic PU-coated (specimen 9)
and Teflon-finished nylon (specimen 8) fabrics, but all exhibited a poor HP, demonstrating
the superior breathability of the microporous PU coating compared to the hydrophilic
PU one. This is in agreement with prior findings [26–28]. Scott [26] reported that the
water vapor permeability of the microporous PU-coated fabrics was superior to that of the
hydrophilic PU-coated fabrics. Saltz [27] also reported that the microporous PU-coated
fabric exhibited a higher water vapor permeability than that of the hydrophilic PU-coated
fabric. Holmes [28] also reported that the various fabrics arranged in decreasing order of
WVP are PTFE laminate > microporous PU coating > hydrophilic coating fabrics. In group
D with nylon/cotton-laminated breathable fabrics, the WVP of the fabric (specimen 11)
with a low cover factor (WDC) was higher than that of the higher one (specimen 10). This
phenomenon was found between specimens 1 and 3 in group A, between specimens 9 and
10 in group C, i.e., laminated or coated breathable fabrics with a low cover factor exhibited
a high WVP. These results are consistent with the previous finding [17]. They reported that
the water vapor permeability decreased with the fabric cover factor in statistical modeling
analysis of water vapor transport through woven fabrics. On the other hand, the HP of
the breathable fabric with a high cover factor was higher than that of the fabric with a low
cover factor, which was between specimens 1 and 2, between specimens 4 and 5, between
Coatings 2022, 12, 12 10 of 13

specimens 9 and 10, and between specimens 11 and 12, i.e., specimens 1, 4, 9, and 12 with
greater cover factors showed a higher HP than did specimens 2, 5, 10, and 11 with smaller
cover factors. These results suggest that a smaller cover factor indicates a better WVP
but inferior waterproofing. In addition, the WR of the breathable fabric was primarily
dependent on the HP of waterproof characteristics because HP (waterproof) is an extreme
case of the WR, as mentioned previously. As shown in Table 2, the WR of the breathable
fabrics showing an HP above 6000 mmH2 O exhibited 100% water-repellency. On the other
hand, the WR of specimens 6 and 7 (1 layer) showing a low HP below 1000 mmH2 O
exhibited a low value of 90%. Specimen 8 (1 layer) treated with a Teflon finish showed a
100% WR. These results suggest that the 100% water repellency of high-density nylon fabric
is due to the Teflon finish, but, even with a Teflon finish, the waterproof characteristics
could not be obtained as with the high-density one-layer fabric. Hence, a coating or
laminating treatment is a prerequisite to achieving a superior waterproof property above
an HP of 6000 mmH2 O and 100% water repellency. In addition, superior waterproof-
breathable characteristics with 100% water-repellency were achieved by treatment with
a hydrophilic laminated finish using a nylon woven fabric with a cover factor between
0.7 and 0.9, considering the water repellency, waterproofing, and breathability of a 2.5-
layered nylon-laminated fabric specimen (specimen 3), which was best specimen for the
waterproof-breathable characteristics.

3.4. Effect of Fabric Structural Parameters and Surface Modification to WVP

The previous section showed that a water-repellent finish or coating and laminat-
ing finishes are required to achieve waterproofing or water repellency. In particular, a
relevant fabric density with a multilayer is needed to achieve a breathable fabric with
a high hydraulic pressure (waterproof). Therefore, the relationship between WVP and
fabric structural parameters was investigated (Figure 4). Furthermore, regression analysis
was carried out to determine which parameters were the most important for obtaining
superior waterproof-breathable fabrics (Table 4). Figure 4 presents the WVP against the
thickness/weight and cover factor of the 12 fabric specimens. As shown in Figure 4, the
water vapor permeability of the breathable fabric increased with decreasing fabric cover
factor and the thickness per unit weight of the fabric. In other words, a high WVP was
observed in the fabrics with a low cover factor and low thickness per unit weight of fabrics
in the coated and laminated breathable fabrics, which is in accordance with a previous
finding [17] as mentioned previously.

Table 4. Regression analysis between the MVP and fabric structural parameters.

Water Vapor
Fabric Stuructural Reg. p-Value
Permeability Regression Equation R2
Parameter (xi ) Coeff. (α = 0.05)
(WVP)
x1 = thickness
WVP by x2 = weight y = −312.5 − 81276.2 x1 + 1127124.5 x2 +
0.801 0.642 0.095
4 vaiables x3 = thickness/weight 12016.2 x3 − 5412.72 x4
x4 = cover factor
x1 = thickness
x2 = weight
WVP by y = 1124.2 − 84612.5 x1 + 1141213.4 x2 +
x3 = thickness/weight 0.805 0.648 0.020
5 variables 9376.5 x3 − 5542.2 x4 − 248.4 x5
x4 = cover factor
x5 = layer
Coatings 2022, 12, 12 11 of 13

Figure 4. WVP against fabric structural parameters.

On the other hand, superior water repellency and waterproof characteristics were
shown in the high-cover-factor fabric with appropriate fabric thickness, which was ex-
amined in Section 3.2. However, high-cover-factor fabrics may limit its applications for
outdoor clothing because of a poor tactile hand feel due to a high cover factor. Therefore,
regression analysis was performed to examine the regression coefficient and determina-
tion coefficient (R2 ) of the fabric structural parameters and surface modification treatment
affecting the excellent water-repellency and waterproof-breathable characteristics of breath-
able fabrics. Table 4 lists the regression equations, regression coefficient, and R2 between
the WVP and fabric structural parameters using a backward regression. ANOVA (F-test)
was carried out to verify the statistical significance of the regression result. As shown in
Table 4, the WVP regression equation by four variables was statistically insignificant, as
F0 (V/Ve) < F (4, 7, 0.95) and p > 0.05, but the WVP regression equation by five variables
was statistically significant, as F0 (V/Ve) > F (5, 6 0.95) and p < 0.05.
According to regression analysis, the determination coefficient (R2 ) between WVP
and the four types of fabric structural parameters was 0.642 with a 5% significance level,
which was not significant, as p > 0.05, but R2 between WVP and the five types of fabric
structural parameters was 0.648 with a 5% significance level, which was significant as
p < 0.05 This means that the fabric structural parameters make a 64.8% contribution to
the WVP, whereas the surface modification method affecting the WVP, such as coating
and laminating, made a 35.2% contribution. Of fabric structural parameters, the cover
factor and thickness/weight are the most important factors influencing the WVP, according
to backward regression analysis, which is consistent with previous findings [17,25]. Lee
and Obendorf [17] reported that fabric thickness, fabric cover factor, pore diameter, and
moisture regain of fibers were significant parameters affecting water vapor transmission
through regression analysis using fifteen woven fabrics. Kim [25] reported that the WVP of
PET-breathable fabrics measured using the inverted cup method was highly dependent on
the fabric density by the curvilinear regression analysis.

4. Conclusions
The water repellency, waterproofing, and water vapor permeability of the twelve
types of waterproof-breathable fabric were examined. Their characteristics were compared
and discussed in terms of surface modification, such as coating and laminating, as well as
Coatings 2022, 12, 12 12 of 13

fabric structural parameters in terms of cover factor, thickness, and weight of fabrics. A
water-repellent finish or surface modification treatment, such as coating and laminating,
is a prerequisite to achieving waterproofing or water-repellency, irrespective of materials
and fabric structural parameters. Of the surface modifications assessed, the laminating
method is pertinent to obtaining superior waterproofing above 6000 mmH2 O, as shown
in specimens 1 and 3 in Group A, specimen 4 in Group B, and specimen 12 in Group
D and is superior to the coating method. Superior waterproof-breathable characteristics
with 100% water-repellency were achieved by treatment with a hydrophilic laminated
finish using nylon woven fabric with a cover factor between 0.7 and 0.9 in a 2.5-layered
fabric (specimen 3 in Group A), which was the best specimen with waterproof-breathable
characteristics. A high WVP was observed in the fabrics with a low cover factor (WDC) and
low thickness per unit weight of the fabric in the coated and laminated breathable fabrics,
whereas superior water repellency and waterproof characteristics were observed in the
high-cover-factor fabric with appropriate fabric thickness. The determination coefficient
(R2 ) from regression analysis between the WVP and fabric structural parameters was 64.8%,
with a 5% significance level. This indicates a higher contribution of the fabric structural
parameters than surface modification factors, such as coating and laminating to the WVP.
According to the backward regression analysis, the cover factor was the most important
factor influencing the WVP of the waterproof-breathable fabrics. This regression analysis
would be valid for coated and laminated breathable fabrics with specifications within
the range of the specimens used in this study. While based on statistics of a specimen
population, these findings are of practical use for engineering coated and laminated fabrics
with high water vapor permeability. Finally, based on the WR, waterproof, and WVP
characteristics of the coated and laminated breathable fabrics, the laminating method,
as an eco-friendly process, is recommended for obtaining better waterproof-breathable
fabrics instead of the coating method, and further studies on the effects of different types
of membranes to breathability are needed in relation to the eco-friendly process for the
coating and laminating treatments in the future.

Funding: This research is supported by Ministry of Culture, Sports and Tourism and Korea Creative
Content Agency (Project Number: R 2019020030) and Ministry of SMEs and Startups (Project Number:
S 3046102).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data sharing is not applicable to this article.
Conflicts of Interest: The author declares no conflict of interest.

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