Introduction
Materials and methods
Materials
Preparation of PVOH, kaolin dispersions and coatings
PVOH content/wt% | Kaolin content/wt% | Degree of crystallinity/% |
---|---|---|
100.0 | 0 | 47.0 ± 0.5 |
98.9 | 1.1 | 37.1 ± 5.3 |
97.0 | 3.0 | 43.5 ± 0.2 |
95.0 | 5.0 | 48.1 ± 0.4 |
89.8 | 10.2 | 40.9 ± 0.2 |
80.0 | 20.0 | 45.1 ± 0.5 |
Permeability methods
Characterization of the material
Fourier transform IR spectroscopy
Differential scanning calorimetry
Permeability model
Symbol | Name | Eq. no. | Definition/property | |
---|---|---|---|---|
Pure component |
\(\rho_{i}\)
\(p_{i}\)
\(T_{i}\), \(M_{i}\)
| Density, pressure, temperature, and molar mass of pure component i
| Tabulated values | |
\(\rho_{i}^{*}\)
\(p_{i}^{*}\)
\(T_{i}^{*}\)
| Characteristic density, pressure, and temperature of pure component i
| Tabulated values | ||
\(r_{i}^{0}\)
| Number of lattice sites occupied by a mole of pure component i
| 6 |
\(r_{i}^{0} = \frac{{M_{i} }}{{\rho_{i}^{*} v_{i}^{*} }}\)
| |
\(v_{i}^{*}\)
| Volume occupied by a mole of lattice sites of pure substance | 7 |
\(v_{i}^{*} = \frac{{RT_{i}^{*} }}{{p_{i}^{*} }}\)
| |
\(\omega_{i}\)
| Mass fraction of i in amorphous phase | |||
\(\phi_{i}\)
| Volume fraction | 8 |
\(\phi_{i} = \frac{{\omega_{i} /\rho_{i}^{ * } }}{{\mathop \sum \nolimits_{i} \omega_{i} /\rho_{i}^{ * } }}\)
| |
Multicomponent |
\(\rho^{ * }\)
| Characteristic density of the mixture | 9 |
\(\frac{1}{{\rho^{ * } }} = \mathop \sum \limits_{i} \frac{{\omega_{i} }}{{\rho_{i}^{ * } }}\)
|
\(\tilde{\rho }\)
| Reduced mixture density | 10 |
\(\tilde{\rho } = \left( {1 - \omega_{i} } \right)\rho_{i} /\rho^{ * }\)
| |
\(p^{ * }\)
| Characteristic pressure of the mixture | 11 |
\(p^{ * } = \mathop \sum \limits_{i} \phi_{i} p_{i}^{ * } - \frac{1}{2}\mathop \sum \limits_{i} \phi_{i} \mathop \sum \limits_{j \ne i} \phi_{j} \Delta p_{ij}^{ * }\)
| |
\(\Delta p_{ij}^{ * }\)
| Binary parameter | 12 |
\(\Delta p_{ij}^{ * } = p_{i}^{ * } + p_{j}^{ * } - 2\left( {1 - k_{ij} } \right)\sqrt {p_{i}^{ * } p_{j}^{ * } }\)
| |
\(k_{ij}\)
| Binary interaction coefficient | 13 | ||
\(r\)
| Molar average number of lattice sites, \(x_{i}\), occupied by a molecule in the mixture | 14 |
\(r = \mathop \sum \limits_{i} x_{i} r_{i}^{0}\)
| |
\(T^{ * }\)
| Characteristic temperature of the mixture | 15 |
\(T^{ * } = \frac{{p^{ * } }}{r}\mathop \sum \limits_{i} x_{i} r_{i}^{0} \frac{{T_{i}^{ * } }}{{p_{i}^{ * } }} = \frac{{p^{ * } v^{ * } }}{R}\)
| |
\(v^{ * }\)
| Average close-packed per molar volume in the mixture | 16 |
\(v^{ * } = \frac{{RT^{ * } }}{{P^{ * } }}\)
| |
Sanchez–Lacombe equilibrium EoS | 17 |
\(\left( {\frac{\rho }{{\rho^{ * } }}} \right)^{2} + \frac{p}{{p^{ * } }} + \frac{T}{{T^{ * } }}\left[ {\ln \left( {1 - \frac{\rho }{{\rho^{ * } }}} \right) + \frac{\rho }{{\rho^{ * } }}\left( {1 - \frac{1}{r}} \right)} \right] = 0\)
| ||
\(\mu_{1}^{\rm NE}\)
| Chemical potential of species i in the nonequilibrium glass (amorphous) | 18 |
\(\begin{aligned} \frac{{\mu_{1}^{\rm NE} }}{RT} & = \ln \left( {\tilde{\rho }\phi_{i} } \right) - \ln \left( {1 - \tilde{\rho }} \right)\left[ {r_{i}^{0} + \frac{{r_{i} - r_{i}^{0} }}{{\tilde{\rho }}}} \right] - r_{i} \\ & \quad - \tilde{\rho }\frac{{r_{i} v_{i}^{ * } }}{RT}\left[ {p_{i}^{ * } + \mathop \sum \limits_{j = 1}^{{N_{p} + 1}} \phi_{j} \left( {p_{j}^{ * } - \Delta p_{ij}^{ * } } \right)} \right] \\ \end{aligned}\)
| |
Si
| Penetrant solubility coefficient |
\(S_{i} = \frac{{n_{i} /V}}{{p_{i} }}\)
| ||
19 |
\(S_{\text{SC}} = S_{\text{am}} \left( {1 - \phi_{\text{C}} } \right)\)
|
Symbol | Name | Eq. no. | Definition/Property | |
---|---|---|---|---|
Diffusion |
\(D\)
| Diffusivity | 20 |
\(D = L\frac{{\partial \mu_{i} /RT}}{{\partial \ln \omega_{i} }} \mathop \Rightarrow \limits_{{\omega_{1} \to 0}} L\)
|
\(E_{\text{a}}\)
| Activation energy | |||
A | Constant | |||
\(L\)
| Mobility (amorphous) | 21 |
\(L_{\text{am}} = Ae^{{ - E_{\text{a}} /{\text{RT}}}}\)
| |
22 |
\(L_{\text{SC}} = L_{\text{am}} \left( {1 - \phi_{\text{C}} } \right)\)
| |||
Tortuosity |
\(\tau_{ff}\)
| Tortuosity30
| 23 |
\(\tau_{ff} = \left\{ {\begin{array}{*{20}c} {r \le 1 \begin{array}{*{20}c} {\frac{{\left( {\alpha \phi } \right)^{2} \left( {1 + 1/\alpha } \right)^{4} }}{{1 - \phi \left( {1 + 1/\alpha } \right)}} + \frac{\alpha \phi }{\pi /4}\left( {1 + \frac{1}{\alpha }} \right)^{2}} \\ {*\ln \left( {\frac{{1 - \phi \left( {1 + 1/\alpha } \right)}}{{\left( {\pi /2} \right)\phi \left( {1 + 1/\alpha } \right)}}} \right)} \\ \end{array} } \\ {r \ge 1 \alpha \phi + \frac{\alpha \phi }{\pi /4}\left( {1 + \frac{1}{\alpha }} \right)^{2} \ln \left( {\frac{{\alpha \left( {1 + 1/\alpha } \right)}}{{\left( {\pi /2} \right)}}} \right)} \\ \end{array} } \right.\)
|
\(r_{\tau }\)
| Control parameter | 24 |
\(r_{\tau } = \frac{\alpha - \phi \alpha }{{\phi \alpha^{2} }}\)
| |
\(\alpha\)
| Aspect ratio | 25 |
\(\alpha = \frac{{S_{n} }}{{S_{L} }} ( {\text{in 3D)}}\)
| |
Permeability |
\(P_{\text{eff}}\)
| Permeability | 26 |
\(P_{\text{eff}} = \left( {1 - \phi_{C} } \right)^{2} L\frac{{\omega_{i} }}{p}\tau_{ff} \left( {1 + \frac{{3\upsilon_{A} }}{{\frac{p + 2}{p - 1} - \upsilon_{A} }}} \right)\)
|
\(p\)
| Relationship of permeability of the composite in dry condition \(P_{\text{composite}}\) and humid condition \(P_{\text{water}}\)
| 27 |
\(p = \frac{{P_{\text{water}} }}{{P_{\text{composite}} }}\)
| |
\(\upsilon_{A}\)
| Volume fraction of the phases |
Results and discussion
Characterization of the material
Permeability
Modeling permeability
Parameter | Value | Units | References |
---|---|---|---|
ρ
PVOH (amorphous) | 1.12 | g cm−3
| |
\(M_{{\text{O}}_2}\)
| 32 | g mol−1
| |
L
0 (amorphous PVOH) | 1 × 10−11 (H = 98%) | cm2 s−1
| |
T*PVOH+water
| 511 (20% RH) | K | This work |
483 (50% RH) | |||
457 (80% RH) | |||
\({T^*}_{{\text{O}}_2}\)
| 170 | K | |
ρ*PVOH+water
| 1.49 (20% RH) | kg m−3
| This work |
1.44 (50% RH) | |||
1.39 (80% RH) | |||
\({\rho^*}_{{\text{O}}_2}\)
| 1.29 | kg m−3
| |
p*PVOH+water
| 2851 (20% RH) | MPa | This work |
2785 (50% RH) | |||
2722 (80% RH) | |||
\({p^*}_{{\text{O}}_2}\)
| 280 | MPa | |
p
| 1000 (20% RH) | This work | |
2500 (50% RH) | |||
4000 (80% RH) | |||
\(\upsilon_{A}\)
| 0.2 (20% RH) | This work | |
0.5 (50% RH) | |||
0.8 (80% RH) |