SYNTHESIS, MODIFICATION, AND CHARACTERISATION OF FUNCTIONAL POLYURETHANE COATING SYSTEMS FROM CASTOR OIL
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Environmental challenges have driven production science towards using biodegradable and
sustainable feedstocks for product development. Developing sustainable and high-performance
coating materials to address the environmental concerns and technical demands of modern
industries has become so critical that plant seed oils are considered viable renewable feedstocks
capable of substituting petrochemical-based materials in polymeric material preparation. This
study reports the synthesis and characterisation of functional organic polyurethane coatings
from castor bean seed oil (CSO) (Ricinus communis seed oil). Graphene nanoparticles were
modified into graphene oxide and incorporated within the polyurethane polymer matrix in a
one-pot synthesis. Also, aminopropyltrimethoxysilane (APTMS) was used to alter silica
nanoparticles and was incorporated into the polyurethane system. Bisphenol A and
trimethylolpropane (TMP) were used as extenders, and their influences on the coating
properties were also examined in the urethane systems. Physicochemical analysis of the
feedstock and prepared coating formulations was conducted. Structural evaluation of
synthesised materials was performed using proton nuclear magnetic resonance (1H NMR) and
attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. Synthesised
urethane coatings were cured on silicon resin mould and mild steel. Thermal stability and
crystallinity of pristine and composite films were studied using thermogravimetric analysis
(TGA) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to analyse
surface morphology. Water contact angle analysis revealed the hydrophobicity of the
synthesised urethane films. Solubility, anticorrosive, and antimicrobial properties of prepared
materials were evaluated. Spectroscopic analysis confirmed the structure of modified
nanomaterials, pristine, and composite films. Surface morphology and photographic images
showed successful incorporation of nanomaterials (graphene oxide and hybrid APTMSmodified
silica) within the polymer matrix. Thermal stability, anti-corrosive, and antimicrobial
properties of the coating films were enhanced with increasing percentages of nanomaterials in
the polyurethane systems. Coating films exhibited improved hydrophobicity with rising
percentages of modified nanoparticles. Film photographic retention tests showed no particle
agglomeration and high transparency at 0.5% graphene oxide composition (0.5% PU-GO). It
also shows that the polymer with 0.5% PU-GO is the most thermally stable. Similarly,
composite films of modified silica in CSO showed enhanced thermal stability, hydrophobicity,
antimicrobial activity, and corrosion resistance. The polymer with 5% PU-SNP was the most
thermally stable at high temperatures. It also has the highest water contact angle and lowest
corrosion rate, hence the most hydrophobic and corrosion resistant. In conclusion, the 0.5%
loading of modified graphene oxide (0.5% PU-GO) nanoparticles is the optimum loading in
applications requiring low and high temperatures. At the same time, 5% loading is the optimum
loading of APTMS-modified silica (5% PU-SNP) in applications that require high temperature.
These results present a viable, sustainable alternative for various industrial applications.
Keywords
QD Chemistry