Electrical and optical properties of plasma treated jute

Abstract

Low temperature plasma (LTP) treatment, a kind of environmentally friendly surface modification technique, was applied to biodegradable and ligno-cellulosic jute fibre with the use of two nonpolymerizing gases, namely argon (Ar) and oxygen (O2) at various discharge powers level of 50, 75 and 100 W and exposure times of 5, 10, 15 and 20 min. with a flow rate of 0.2 L/min. The surface morphology, chemical structure, thermal, optical, direct current (DC) and alternating current (AC) electrical properties of both raw and LTP treated jute were studied at various discharge power levels and exposure times. By means of the scanning electron microscopy (SEM), the influence of treatment time and discharge power on the surface morphology of the surface of LTP treated jute were studied and compared with that of raw jute. SEM microphotographs reveal that the roughness of the fibre surfaces increases with the increase of discharge power and exposure time. This is caused due to the bombardment of high energetic ions on the fibre surface and the fibres become sputtered. The analyses of the chemical structure of raw jute and plasma treated jute fibre by fourier transform infrared (FTIR) spectroscopy showed similar spectra with the change in the peak intensity and shift in the peak position. From FTIR spectra, the changes at the bands around 1730, 1650, 1235, 1077, 1030 and at 890 cm-1 revealed surface chemistry of fiber changes after plasma treatment. FTIR has given the evidence of moisture removal from the fibre. From differential thermal analysis, it is seen that the fibres degradation temperatures for both the celluloses and hemicelluloses were unstabled. Thermogravimetric analysis (TGA) is applied to measure the mass loss of the of raw and LTP treated jute samples as a function of temperature. It is seen from the TGA traces that the percentages of the moisture content of the LTP treated fibre by the O2 are the higher than that of the fibre treated by the Ar plasma. Ultraviolet Visible spectroscopic analysis reveals that the band gap of jute increases with the increase of discharge power as well as exposure time. The increase of the DC electrical resistivity of the LTP-treated jute fibre was in good agreement with the above findings. The capacitance and the AC electrical conductance of both raw and LTP treated jute were measured as a function of frequency (50 Hz. to 120 MHz.) at room temperature. The dielectric constant r, AC conductivity (ac) and dielectric loss tangent (tanδ) of both raw and LTP treated jute as a function of frequency were studied at room temperature. It is observed that for all the samples the r almost constant at lower frequencies and then decreases gradually very sharply in the high frequency region. In addition, r increases with increase plasma treatment times as well as discharge powers. It is also observed for all the samples that the ac increases as the frequency increases with a lower slope in the low frequency region and with a higher slope in the higher frequency region. In addition, the values of ac decrease with increase of plasma exposure times as well as discharge powers. The ac increases with frequency due to the hopping mechanism of electrons. The dependence of the tanδ with frequency at different treatment times and discharge powers for all the jute samples show small relaxation peaks at the very low frequency region. The values of tanδ decrease with the increases of both plasma treatment times and discharge powers. Also, the relaxation peaks shifted to the higher frequency region as the plasma treatment times as well as discharge power increases. At low frequencies relaxation peaks indicates the possibility for the interfacial polarization.