Synthesis and Characterization of Alkyd Resin Microcapsules - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 231

Chapter 21
synthesis and Characterization of alkyd resin
microcapsules
Hariharan Raja, Swarupini Ganesan, Gokulnath Dillibabu,
and Ravisankar Subburayalu
iNtroduCtioN
Microencapsulation enables storing of reactive components in a hollow sphere which
has been used for variety of applications such as pharmaceuticals, textiles, adhesives,
cosmetics, nutrient retention, and advanced coatings. Recently, microcapsules in the
form of microscopic spheres containing “Healants” or “coating repairing” compounds
are involved in self-healing mechanism (Ashok Kumar et al., 2006; Dong Yang Wu
et al., 2008). Upon damage-induced cracking, the microcapsules containing heal-
ing agents are ruptured by the propagating crack fronts resulting in the release of the
healing agent into the cracks by means of capillary action. These microcapsules can
be manufactured by various methods of polymerization techniques (Erin B. Murphy
et al., 2010).
Poly(urea-formaldehyde) (UF) microcapsules prepared by in situ polymerization
of urea and formaldehyde meet the demanding criteria required for use in self-healing
materials (Suryanarayanaa, 2008). These criteria includes excellent bonding to the
matrix, sequestration of the healing monomer from the surrounding environment, and
rupture and release of the monomer into the crack plane upon matrix damage (Blaiszik
B. J., 2009).
Here, we report on the development of urea-formaldehyde microcapsules filled
with fast drying alkyd resin and xylene as a solvent for its use in self-healing. Not all
resins are suitable for self-healing. Alkyd resin has fast drying property, film forming
ability by atmospheric oxidation, self-healing property, surface transparency, and low
flammability. Alkyd resin, being cost effective and commercially available resin it
could be the suitable replacement for other resins which had been used for self-healing
coatings.
eXPerimeNtal ProCedure
microcapsule materials
Fast drying alkyd resin obtained from soya oil is used as a core material and mixed
xylene is used as a solvent (to reduce the viscosity of the resin). Urea, formaldehyde,
resorcinol and ammonium chloride were the wall forming materials. Polyvinyl alcohol
as a surfactant and n-octanol as an anti-foaming agent supports to achieve high yield
of microcapsules without any air filled capsules.