dc.description.abstract | Vernonia oil and other epoxidized vegetable oils were studied for
their characteristics and evaluated for their applications as
reactive diluents in alkyd coatings and in elastomers for
toughening epoxy coatings. These oils are compatible with short
oil, medium oil and long oil alkyds. Their degree of epoxidation
was found to be related to their densities, viscosities
unsaturation and rate of cure of alkyd coatings (with the oils as
reactive diluents). The oils helped to lower volatile organic
compounds (VOC), drying time and application viscosity of alkyd
based paints. The paints maintained package (can) stability very
well. Coatings formed had excellent adhesion, flexibility, impact
resistance and had good specular gloss. The oils did not enhance
degradation of the coatings by UV. Compared with synthetic reactive
diluents, introduction of these oils into alkyd coatings would be
simpler and possibly involve less capital investment. They are
cheaper with little or no toxicity. Th ir use would reduce
pollution to the atmosphere and save on expensive solvents and
energy. Two phase epoxy coatings were made from DGEBA epoxy resin
(EPON 828), commercial 4,4'-diaminodiphenylmethane (DDM) and
epoxidized vegetable oil liquid rubber. Below 20% rubber content,
discrete rubbery particles of the order of 0.2-5 microns were
formed in the epoxy matrix. In this region, microcavitation and
shear band formation were the major toughening mechanisms of the
coatings. Beyond 20% rubber content, phase inversion started in the
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coatings and was complete by 50%. In this region, epoxy coatings
were enhanced by rubber through its flexibilizing and plasticizing
effects. Incorporation of the liquid rubber in the epoxy coatings
helped to improve on impact resistance and flexibility. Adhesion
showed no significant change but remained high throughout. There
was a gradual decrease in hardness as rubber content was increased.
Epoxidized vegetable oils have great potential in alkyd coatings
and elastomers for toughening epoxy coatings. | |