Preparation and Characterization of Conductive Bioplastic Films

Abstract

This laboratory report presents the methodology, materials, and results of the preparation and characterization of conductive bioplastic (CB) films using 2-Hydroxyethyl Cellulose (2-HEC) and ammonium chloride (NH4Cl). The CB films were prepared through a solution casting technique with varying NH4Cl compositions. The materials and methods, experimental procedures, and characterization techniques, including Electrical Impedance Spectroscopy (EIS), Thermogravimetric Analysis Differential Scanning Calorimetry (TGA-DSC), and Texture Analyzer (TA), are discussed in detail. The report also includes tables and equations for data representation and analysis.

1. Introduction

Conductive bioplastic films have gained significant attention due to their potential applications in various fields, including electronics and biomedical devices. This report focuses on the preparation and characterization of CB films based on 2-HEC and NH4Cl. The aim is to investigate the electrical, thermal, and mechanical properties of these films as a function of NH4Cl composition.

2. Materials and Methods

2.1 Materials

The materials used in this research are listed in Table 1. The 2-HEC polymer with an average molecular weight (M.

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W.) of ~90,000 and viscosity of 75-150 Cp was obtained from Sigma Aldrich. Ammonium chloride (NH4Cl) with a purity of 99.8% was also obtained from Sigma Aldrich.

2.2 Procedure

The CB films were prepared using a solution casting technique at room temperature (RT). Two grams of 2-HEC were dissolved in 80 ml of distilled water in a clean beaker. Different amounts of NH4Cl (wt. %) were added to the 2-HEC solution, and the mixture was stirred continuously until homogenous.

The solutions were cast into Petri dishes and left to dry in an oven for 14 hours. The films were stored in a desiccator to remove residual moisture. The composition of 2-HEC-NH4Cl films is detailed in Table 2.

3. Characterization Techniques

3.1 Electrical Impedance Spectroscopy (EIS)

The CB films were characterized using EIS with a HIOKI 3532-02 LCR Hi-Tester in the frequency range from 50 Hz to 1 MHz. The films were cut into 2 cm x 2 cm samples and labeled accordingly. The samples were placed between stainless steel electrodes to determine electrical conductivity. The ionic conductivity (σ) and electrical properties were calculated using Equation 1:

σ = t / (Rb x A) (1)

Where:

• σ = Ionic conductivity (S/m)
• t = Film thickness (m)
• Rb = Bulk resistance (Ω)
• A = Surface area of the film (m²)

3.2 Thermogravimetric Analysis Differential Scanning Calorimetry (TGA-DSC)

The thermal stability of the CB films was studied using TGA-DSC. TGA measured the weight loss as a function of temperature up to 400°C. DSC was used to investigate thermal transitions such as glass transition temperature (Tg), melting (Tm), and crystallization (Tc). Samples were analyzed at a heating rate of 10°C/min under an argon atmosphere.

3.3 Texture Analyzer (TA)

The mechanical properties of the CB films were determined through tensile strength (TS) and elongation at break (EAB). TA was operated according to ASTM standard method D882-02. Eleven rectangular strip specimens were cut for tensile tests, and the results were used to calculate TS and EAB.

4. Results and Discussion

4.1 Electrical Impedance Spectroscopy (EIS)

The EIS results showed that the ionic conductivity (σ) of the CB films increased with increasing NH4Cl content. This indicates that the addition of NH4Cl enhances the electrical conductivity of the films. The bulk resistance (Rb) decreased with higher NH4Cl content, demonstrating improved conductivity.

4.2 Thermogravimetric Analysis Differential Scanning Calorimetry (TGA-DSC)

The TGA-DSC analysis revealed the thermal stability of the CB films. The films exhibited weight loss as the temperature increased. The maximum decomposition temperature (Td) was found to decrease with increasing NH4Cl content, indicating reduced thermal stability. DSC analysis also showed changes in glass transition temperature (Tg), melting (Tm), and crystallization (Tc) with varying NH4Cl compositions, suggesting alterations in the film's thermal properties.

4.3 Texture Analyzer (TA)

The mechanical properties of the CB films were evaluated using TA. The tensile strength (TS) and elongation at break (EAB) were measured. It was observed that TS increased with increasing NH4Cl content, indicating improved mechanical strength. Conversely, EAB decreased with higher NH4Cl content, suggesting reduced flexibility of the films.

5. Conclusion

In conclusion, the preparation and characterization of conductive bioplastic films based on 2-HEC and NH4Cl were successfully carried out. The results indicate that the addition of NH4Cl enhances the electrical conductivity of the films while affecting their thermal stability and mechanical properties. These findings have implications for the potential applications of CB films in various industries, including electronics and packaging.