Improving Thermal Stability and Hydrophobicity of Rutile-TiO2 Nanoparticles for Oil-Impregnated Paper Application

Abstract

Thermal stress and moisture absorption can cause a synergetic negative impact on kraft paper. Among various approaches for improving the dielectric properties of kraft paper, nanotechnology has had promising results. However, the hydrophilicity of most metal oxide nanoparticles renders nanomodified kraft paper more vulnerable to thermal stress and moisture, thereby inducing degradation. In nanomodified kraft paper research, the use of TiO2 nanoparticles has yielded the most promising results. The major shortfall, however, is the hydrophilicity of TiO2. This work investigated surface modifications of rutile-TiO2 nanoparticles (NPs) for improved hydrophobicity and thermal stability. Rutile-TiO2 NPs is a nontoxic metal oxide that can withstand high temperature and is stable in chemical reactions. Two cases of surfactants were used—alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA). The intention was to increase heat resistance and reduce the surface free energy of the rutile-TiO2 NPs. The impacts of the surface modifiers on the rutile-TiO2 NPs were characterised using FT-IR, muffle furnace, analytical weight balance, and TGA. It was discovered that new functional groups were formed on the modified NPs examined through FT-IR spectra. This indicates new chemical bonds, introduced through the surface modification. The unmodified rutile-TiO2 NPs absorbed moisture, increasing their mass by 3.88%, compared with the modified nanoparticles, which released moisture instead. TGA analysis revealed that AKD- and ASA-modified rutile-TiO2 needed higher temperatures than the unmodified rutile-TiO2 to markedly decompose. AKD, however, gave better performance than ASA in that regard. As an example, those modified with 5% AKD sustained a 45% higher temperature than the pure TiO2 nanoparticles. Furthermore, in both cases of the surfactants, the higher the percent of surfactant content was, the more thermally stable the nanoparticles became. This work demonstrates the possibility of fabricating rutile-TiO2 NPs to give improved hydrophobicity and thermal stability for possible dielectric applications such as in kraft paper for power transformer insulation.

Reducing Hydrophilic Characteristics of Kraft Paper Insulation by Reinforcing With Surface Modified Rutile-TiO2 Nanoparticles

“…However, these techniques have the risk of producing toxic byproducts. Consequently, the literature often highlights the need to explore alternative means to improve the thermal stability of kraft paper insulation [4].…”

“…Water in kraft paper increases the paper's dielectric dissipation factor (DDF) due to increased conductivity. The thermal and mechanical properties are entirely compromised as a result of accelerated structural decomposition of the kraft paper [4], [9], [10]. Among the techniques for improving the dielectric properties of kraft paper insulation is the application of nanotechnology.…”

“…TiO2, MgO, ZnO, SiO2, and Al2O3 are the typical metal oxide nanoparticles (NPs) used to modify kraft paper insulation [4], [11]. However, regarding reaction stability, thermal stability, high electrical resistivity, and nontoxicity, TiO2 has been found to be superior among the various alternatives.…”

“…However, regarding reaction stability, thermal stability, high electrical resistivity, and nontoxicity, TiO2 has been found to be superior among the various alternatives. TiO2 has a low cast, and its rutile phase is reported to be chemically stable, has a high dielectric constant, withstands higher temperatures and does not readily decompose as compared with other phases of the TiO2 [4]. However, metal oxide NPs, including TiO2 are hydrophilic.…”

“…However, metal oxide NPs, including TiO2 are hydrophilic. The hydrophilic nanoparticles therefore compromise the effort to improve the dielectric properties of the cellulose nanocomposite kraft paper insulation [4], [17], [18].…”