**2.3 Silane-coupled nanosilica preparation**

The coupling process of nanosilica and silane was done by developing [12] method. A total of 0.03 grams of nanosilica and 0.0075 grams of 3-glycidoxypropyl trimethoxy silane (GPTMS) (nanosilica:silane = 1:0.25) were dissolved in 0.3 mL dimethylformamide (DMF) at room temperature, then stirred using magnetic stirrer for 6 hours. Then the homogeneous solution was put into a beaker and heated in an oven at 60° C for 24 hours. After that, it was heated at 100° C for 1 hour and at 120° C for 2 hours. Drying was carried out at 155° C for 2 hours. The obtained solids were soaked with 1 M HCl solution at 80° C for 24 hours until hydrolysis and condensation occur in the solution. The resulting solids were crushed and sieved with 230 mesh sieves. The final produced powder is nanosilica filler that had been modified with silane coupling agent. Furthermore, the coupling process was also carried out at the ratio of nanosilica: silane = 1:0; 1:0.50; 1:1.0; 1:1.5 and 1:2.0.

#### **2.4 Membrane synthesis by modifying chitosan with silane-coupled nanosilica**

The chitosan membrane synthesis with silane-coupled nanosilica addition by developing [8, 24] method. First, a total of silane-coupled nanosilica (w:w) with nanosilica:silane respectively 1:0; 1:0.25; 1:0.50; 1:1.0; 1:1.5 and 1:2.0 was dissolved in each 50 mL of 2% acetic acid and was stirred at a temperature of 60°C for 7 hours. Secondly, as many as 1 g of chitosan was dissolved in 50 mL of 2% acetic acid at room temperature for 4 hours. Then the first solution and second solution were mixed and stirred for 4 hours at the temperature of 60°C. The homogeneous solution formed is called dope solution that was then poured in the acrylic mold of 20 x 20 cm and was dried in an oven at the temperature of 60°C for 21 hours that produced dry membrane. The process of membrane formation used the phase inversion method.

#### **2.5 Membrane characterization**

The characterization of chitosan-nanosilica membrane with silane addition was performed by water uptake measurement, membrane tensile strength analysis (by tensile test equipment Strograph VG 10-E Toyoseiki), methanol permeability (by diffusion cell method), proton conductivity analysis (by EIS or Electrochemical Impedance Spectroscopy Autolab PG STAT 128 N Instrument) [2], membrane selectivity determination, functional group analysis (by FT-IR PRESTIGE-21 Shimadzu), membrane morphology analysis (by SEM FEI Inspect S50), membrane topography analysis (by AFM Bruker N8 Neos 5.5 IF367), and thermal degradation analysis (by TGA Mettler Star SW 10.00).

Water uptake is the ability of a membrane to absorb water for 24 hours, so it is performed by weighing the mass of absorbed water (w2) and comparing it with the mass of membrane (w1) in a percentage format as expressed in Eq. (1) adopted from [10, 25–27]. In determining the water uptake, demineralized water which is free of metal ions is used.

$$\text{Water update} = \frac{\mathbf{w}\_2 - \mathbf{w}\_1}{\mathbf{w}\_1} \times \mathbf{100\%} \tag{1}$$

**183**

with diffusivity, t0 = L2

400 cm−1 [30, 31].

*Characterization of Chitosan Membrane Modified with Silane-Coupled Nanosilica for Polymer…*

*P A* σ

*L L* ε

ε

Proton conductivity measured by Electrochemical Impedance Spectroscopy as Eq. (5) adopted from [5, 25–27]. Where σ is the proton conductivity (S cm−1), d is the membrane thickness (cm), Rb is the bulk resistance value (Ω) and A is the

> *b d R A*

*B A* ( ) *A DK C C tt*

Where CA is the methanol concentration in compartment A, A and L are the polymer membrane area and thickness, D and K are the methanol diffusivity and the partition coefficient between the membrane and solution, V is solution volume in compartment B and t is permeation time. The result of DK or P is the methanol permeability of membrane (DK = P), and t0 is also called the time lag associated

Membrane selectivity is comparison between proton conductivity and methanol permeability [8] expressed in Eq. (7). Where β is membrane selectivity, σ is proton

> *P* σ β

The chitosan membrane to be analyzed for its functional groups by FT-IR PRESTIGE-21 Shimadzu was taken as much as 0.1–0.2 g. In addition, KBr powder of 0.5–1.0 g was also prepared. The two solids were mixed and grinded until smooth, then the mixture powder was made into pellets with a hydraulic press and the measurement analysis was carried out with a wavelength between 4000 and

Methanol permeability of the membrane is measured by counting the methanol concentration passing the membrane for the diffusion of methanol in progress [16, 26]. The methanol permeability test is carried out using a permeation measurement cell that has two identical compartments. Compartment A is filled with methanol solution in deionized water, and compartment B is filled with deionized water. The principle used cell diffusion between the two compartments. The solution in both compartments is stirred until it is homogeneous so that the diffusion process runs well [14]. Methanol permeability was calculated from the methanol concentration versus permeation time curve. The methanol concentration in compartment B (CB)

∆ = 0

*E* σ

) [2].

σ

), ΔL is the length increase (cm) and L0 is the initial length of

= (2)

<sup>=</sup> (4)

<sup>=</sup> <sup>×</sup> (5)

*V L* <sup>=</sup> <sup>−</sup> <sup>0</sup> (6)

= (7)

(3)

constant cross head speed of 10 mm min−1 and 100 N load cells. The samples were dumbbell-shaped with gauge dimensions of 15 mm × 3 mm × 0.22 mm. Eq. (2) until Eq. (4) describe that σ is tensile strength, ε is elongation break, E is modulus young, P is the force applied to the specimen, A is the specimen cross-

*DOI: http://dx.doi.org/10.5772/intechopen.95580*

membrane area in the sample (cm<sup>2</sup>

is obtained from the Eq. (6) adopted from [25, 27].

/ 6D [29].

conductivity, and P is methanol permeability.

sectional area (cm<sup>2</sup>

the specimen (cm).

The mechanical strength test is generally measured by tensile strength test, in which material sample of a certain size is exerted with force and pulled until it breaks. Eq. (2) until Eq. (4) express the equation for determining tensile strength, elongation break and modulus young adopted from [10, 28]. Tensile strength test performed according to ASTM D882 at room temperature at a

*Characterization of Chitosan Membrane Modified with Silane-Coupled Nanosilica for Polymer… DOI: http://dx.doi.org/10.5772/intechopen.95580*

constant cross head speed of 10 mm min−1 and 100 N load cells. The samples were dumbbell-shaped with gauge dimensions of 15 mm × 3 mm × 0.22 mm. Eq. (2) until Eq. (4) describe that σ is tensile strength, ε is elongation break, E is modulus young, P is the force applied to the specimen, A is the specimen crosssectional area (cm<sup>2</sup> ), ΔL is the length increase (cm) and L0 is the initial length of the specimen (cm).

$$
\sigma = \frac{P}{A} \tag{2}
$$

$$
\varepsilon = \frac{\Delta L}{L\_0} \tag{3}
$$

$$E = \frac{\sigma}{\varepsilon} \tag{4}$$

Proton conductivity measured by Electrochemical Impedance Spectroscopy as Eq. (5) adopted from [5, 25–27]. Where σ is the proton conductivity (S cm−1), d is the membrane thickness (cm), Rb is the bulk resistance value (Ω) and A is the membrane area in the sample (cm<sup>2</sup> ) [2].

$$
\sigma = \frac{d}{R\_b \times A} \tag{5}
$$

Methanol permeability of the membrane is measured by counting the methanol concentration passing the membrane for the diffusion of methanol in progress [16, 26]. The methanol permeability test is carried out using a permeation measurement cell that has two identical compartments. Compartment A is filled with methanol solution in deionized water, and compartment B is filled with deionized water. The principle used cell diffusion between the two compartments. The solution in both compartments is stirred until it is homogeneous so that the diffusion process runs well [14]. Methanol permeability was calculated from the methanol concentration versus permeation time curve. The methanol concentration in compartment B (CB) is obtained from the Eq. (6) adopted from [25, 27].

$$\mathbf{C}\_{B} = \frac{A}{V} \frac{DK}{L} \mathbf{C}\_{A} \left(t - t\_{0}\right) \tag{6}$$

Where CA is the methanol concentration in compartment A, A and L are the polymer membrane area and thickness, D and K are the methanol diffusivity and the partition coefficient between the membrane and solution, V is solution volume in compartment B and t is permeation time. The result of DK or P is the methanol permeability of membrane (DK = P), and t0 is also called the time lag associated with diffusivity, t0 = L2 / 6D [29].

Membrane selectivity is comparison between proton conductivity and methanol permeability [8] expressed in Eq. (7). Where β is membrane selectivity, σ is proton conductivity, and P is methanol permeability.

$$
\beta = \frac{\sigma}{P} \tag{7}
$$

The chitosan membrane to be analyzed for its functional groups by FT-IR PRESTIGE-21 Shimadzu was taken as much as 0.1–0.2 g. In addition, KBr powder of 0.5–1.0 g was also prepared. The two solids were mixed and grinded until smooth, then the mixture powder was made into pellets with a hydraulic press and the measurement analysis was carried out with a wavelength between 4000 and 400 cm−1 [30, 31].

*Chitin and Chitosan - Physicochemical Properties and Industrial Applications*

The coupling process of nanosilica and silane was done by developing [12] method. A total of 0.03 grams of nanosilica and 0.0075 grams of 3-glycidoxypropyl trimethoxy silane (GPTMS) (nanosilica:silane = 1:0.25) were dissolved in 0.3 mL dimethylformamide (DMF) at room temperature, then stirred using magnetic stirrer for 6 hours. Then the homogeneous solution was put into a beaker and heated in an oven at 60° C for 24 hours. After that, it was heated at 100° C for 1 hour and at 120° C for 2 hours. Drying was carried out at 155° C for 2 hours. The obtained solids were soaked with 1 M HCl solution at 80° C for 24 hours until hydrolysis and condensation occur in the solution. The resulting solids were crushed and sieved with 230 mesh sieves. The final produced powder is nanosilica filler that had been modified with silane coupling agent. Furthermore, the coupling process was also carried out at the ratio of nanosilica: silane = 1:0; 1:0.50; 1:1.0; 1:1.5 and 1:2.0.

**2.4 Membrane synthesis by modifying chitosan with silane-coupled nanosilica**

The chitosan membrane synthesis with silane-coupled nanosilica addition by developing [8, 24] method. First, a total of silane-coupled nanosilica (w:w) with nanosilica:silane respectively 1:0; 1:0.25; 1:0.50; 1:1.0; 1:1.5 and 1:2.0 was dissolved in each 50 mL of 2% acetic acid and was stirred at a temperature of 60°C for 7 hours. Secondly, as many as 1 g of chitosan was dissolved in 50 mL of 2% acetic acid at room temperature for 4 hours. Then the first solution and second solution were mixed and stirred for 4 hours at the temperature of 60°C. The homogeneous solution formed is called dope solution that was then poured in the acrylic mold of 20 x 20 cm and was dried in an oven at the temperature of 60°C for 21 hours that produced dry membrane. The process of membrane formation used the phase

The characterization of chitosan-nanosilica membrane with silane addition was performed by water uptake measurement, membrane tensile strength analysis (by tensile test equipment Strograph VG 10-E Toyoseiki), methanol permeability (by diffusion cell method), proton conductivity analysis (by EIS or Electrochemical Impedance Spectroscopy Autolab PG STAT 128 N Instrument) [2], membrane selectivity determination, functional group analysis (by FT-IR PRESTIGE-21 Shimadzu), membrane morphology analysis (by SEM FEI Inspect S50), membrane topography analysis (by AFM Bruker N8 Neos 5.5 IF367), and thermal degradation

Water uptake is the ability of a membrane to absorb water for 24 hours, so it is performed by weighing the mass of absorbed water (w2) and comparing it with the mass of membrane (w1) in a percentage format as expressed in Eq. (1) adopted from [10, 25–27]. In determining the water uptake, demineralized water which is free of

> w w Water uptake 100% w

The mechanical strength test is generally measured by tensile strength test, in which material sample of a certain size is exerted with force and pulled until it breaks. Eq. (2) until Eq. (4) express the equation for determining tensile strength, elongation break and modulus young adopted from [10, 28]. Tensile strength test performed according to ASTM D882 at room temperature at a

<sup>−</sup> = × 2 1 1

(1)

**2.3 Silane-coupled nanosilica preparation**

**182**

inversion method.

metal ions is used.

**2.5 Membrane characterization**

analysis (by TGA Mettler Star SW 10.00).

The membrane surface morphology was observed using SEM FEI Inspect S50. The membrane (1x1 cm2 ) was firstly coated using gold so that it could be detected by the device.

Membrane topography was observed in three dimensions and two dimensions using AFM Bruker N8 Neos 5.5 IF367. The membrane was taken several parts then put on the tip and detected by the device at certain distance.

Thermal stability analysis using TGA Mettler Star SW 10.00 was carried out on the selected membrane specimens that had the best and worst properties therefore it represented all variations. Thermal stability analysis data was recorded in nitrogen atmosphere at every 10°C/minute heating rate at 30–500°C temperatures.
