Synthesis and properties of novel poly(alkyd-urethane)s derived from various types of vegetable oils
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Date
2014
Authors
Jem Shan, Ling
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Abstract
Triglyceride of oil palm (Elaeis guineensis), soy (Glycine max) and sunflower
(Helianthus annuus) were used to produce novel alkyd diols and poly(alkydurethane)
s with chemical structure specifically designed for better coating
performances. The vegetable oils were first converted to monoglycerides by
glycerolysis process. The monoglycerides derived from the different oils were
reacted with phthalic anhydride at 2:1 monoglyceride-to-phthalic anhydride ratio to
obtain novel polyols called alkyd diols. The polyols were then reacted with 4,4`-
methylenediphenyldiisocyanate (MDI) to produce five novel poly(alkyd-urethane)s
(PAU), namely palm oil based poly(alkyd-urethane) (POPAU), soy oil based
poly(alkyd-urethane) (SOPAU), sunflower oil based poly(alkyd-urethane) (SFPAU),
palm-soy oils based poly(alkyd-urethane) (POSOPAU) and palm-sunflower oils
based poly(alkyd-urethane) (POSFPAU). The successful synthesis of the
monoglycerides, alkyd diols and poly(alkyd-urethane)s were confirmed by FTIR, 1H
NMR, 13C NMR spectroscopy and their morphology were evaluated by scanning
electron microscopy (SEM). The obtained varieties of poly(alkyd-urethane) were
applied onto substrates to study their physical and mechanical properties. Further
analyses prior to application included viscosity, solubility, iodine number testing, gel
content, drying time test while thermogravimetric analysis (TGA), crosshatch
adhesion tests, impact strength, pencil hardness, chemical and water resistance were
employed after the films were cured. The films showed good homogeneity and
impressive thermal stability with palm oil poly(alkyd-urethane) showing only 5%
weight loss temperature in N2 at 270oC. Overall, sunflower oil poly(alkyd-urethane)
exhibited relatively better mechanical and thermal properties among all due to the
highest percentage of cross linked fraction portrayed by its higher iodine value and
gel content. Coating performance of poly(alkyd-urethane) based on palm oil was
enhanced after blending with sunflower oil or soy oil based alkyd-diols. The adopted
technique in the novel chemical design of poly(alkyd-urethane)s created a potential
alternative reaction schemes to be applied in the industry for surface coating, binder
for composites and other applications, aiding the effort to replace or minimize the use of non-sustainable petroleum-based raw material.