Oxygen-containing Polar Functional Groups Research Articles

Changes in electrical and microstructural properties of microcrystalline cellulose as function of carbonization temperature

AC and DC electrical measurements were made to better understand the thermal conversion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstructural evolution of cellulose during carbonization. In Region I (250–350 °C), a decrease in overall AC conductivity occurs due to the loss of the polar oxygen-containing functional groups from cellulose molecules. In Region II (400–500 °C), the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III (550–600 °C), a further increase of AC conductivity with increasing heat treatment temperature is observed. In addition, the AC conductivity demonstrates a non-linear frequency dependency due to electron hopping, interfacial polarization, and onset of a percolation threshold. In Region IV (610–1000 °C), a frequency independent conductivity (DC conductivity) is observed and continues to increase with heat treatment due to the growth and further percolation of carbon clusters. Finally in Region V (1200–2000 °C), the DC conductivity reaches a plateau with increasing heat treatment temperature as the system reaches a fully percolated state.

Gliding arc discharge — Application for adhesion improvement of fibre reinforced polyester composites

A gliding arc enables selective chemical process with high productivity due to its high degree of non-equilibrium and high energy density simultaneously, and thus can be preferably used for a variety of industrial applications such as gas cleaning, pollution control, fuel conversion, hydrogen production, and surface treatment. However, the application for adhesion improvement of structural materials has been rarely reported. In the present work, glass fibre reinforced polyester plates were treated using atmospheric pressure gliding arcs with high speed air flow for adhesion improvement with vinylester resin. It is found that the treatment increased the density of oxygen-containing polar functional groups at the composite surfaces, the polar component of the surface energy, and adhesive strength with a vinylester resin. The treatment effect highly depended on the temperatures of the electrodes and the discharge.

Comparison of the surface characteristics of polypropylene films treated by Ar and mixed gas (Ar/O 2) atmospheric pressure plasma

In an attempt to modify the hydrophobic surface properties of polypropylene (PP) films, this study examined the optimum process parameters of atmospheric pressure plasma (APP) using Ar gas. Under optimized conditions, the effects of a mixed gas (Ar/O 2) plasma treatment on the surface-free energy of a PP film were investigated as a function of the O 2 content. The polar contribution of the surface-free energy of the PP film increased with increasing O 2 content in the gas mixture. However, slightly more oxygen-containing polar functional groups such as CO, C O, and COO were introduced on the PP film surface by the Ar gas only rather than by the Ar/O 2 gas mixture. In addition, AFM analysis showed that the Ar plasma treatment of the PP film produced the smoothest surface as a result of the relatively homogeneous etching process.

Ammonia removal of activated carbon fibers produced by oxyfluorination

In this study, activated carbon fibers (ACFs) were produced by an oxyfluorination treatment to enhance the capacity of ammonia gas removal. The introduction of polar groups, such as CF, CO, and COOH, on the ACFs was confirmed by a XPS analysis, and N2/77 K adsorption isotherm characteristics including specific surface area and total and micropore volumes were studied by the BET and t-plot methods. The ammonia-removal efficiency was confirmed by a gas-detecting tube technique. As a result, the specific surface area and micropore volume of ACFs were slightly destroyed as the surface treatment time was increased. However, the oxyfluorinated ACFs led to an increase of fluorine and oxygen-containing polar functional groups in ACF surfaces, resulting in an increase in the ammonia-removal efficiency of the ACFs produced.