Physico-chemical, thermal and electrical properties of the fabricated polyurethane thin films utilizing bio-based epoxidized soybean oil
We successfully fabricated polyurethane (PU) thin films deposited on glass substrates utilizing bio-based epoxidized soybean oil (ESBO) via spin coating technique. Prior to deposition, one-shot polymerization condensation reaction was made by reacting varied amount of ESBO-based polyols with isocyanate. Visual inspection using stereomicroscope revealed that both petroleum-based and ESBO-based polyols polyurethane exhibit homogeneous and superior quality thin films as confirmed by scanning electron microscope (SEM) images. Furthermore, Fourier transform infrared (FTIR) spectra showed a higher N-C-O vibrational mode transmission for bio-based polyols while lower vibrational mode transmission for petroleum-based polyols. On the other hand, FTIR spectra showed a higher O-H vibrational mode transmission for bio-based polyols while lower for the petroleum-based polyols. This phenomenon may trigger a stoichiometric ratio closer to unity between polyols and isocyanate that will significantly produce a homogeneous thin film deposition. Moreover, fabrication of uniform thin films was also influenced by the spin coating speed. The fabricated PU thin films utilizing ESBO-based polyols exhibit a higher thermal stability as indicated in the thermogravimetric analysis (TGA).
Keywords: Polyurethane; epoxidized soybean oil; spin coating; thin films