Synthesis and Characterization of Alkyd Resin Microcapsules - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 232

encapsulation technique
The encapsulation method was adapted from that of (Brown et al., 2003). Microcap-
sules containing a mixture of resin and solvent were prepared by in situ urea-form-
aldehyde microencapsulation procedure. 260 ml of deionised water is mixed with 10
ml of 5 wt% aqueous solution of polyvinyl alcohol in a 1000 ml beaker and is kept
over a hot plate. The solution is agitated using REMI Mechanical stirrer consisting of
4 bladed low shear mixing propeller each of 40mm diameter, placed above the bot-
tom of beaker. Under agitation, 5 g of urea, 0.5 g of ammonium chloride and 0.5 g of
resorcinol were added to the solution. After agitation for 5 min, pH was adjusted to
approximately 3.5 by using 5wt% solution of hydrochloric acid in deionised water.
One to two drops of n-octanol was added to reduce foam.
A slow stream of 60 ml of alkyd resin and solvent containing 0.05 wt% cobalt
octoate, 0.5 wt% lead octoate and 0.05 wt% manganese octoate driers were added
slowly to form an emulsion and allowed to stabilize for 10 min under agitation. After
stabilization, 12.67 g of 37 wt% aqueous solution of formaldehyde was added. The
temperature is increased at a rate of 1°C/min upto 45°C under stirring at 200 rpm and
maintained at this temperature for 4 hr. Contents were cooled to ambient temperature.
Microcapsules from the suspension were recovered by sieve filtration through a stack
of 3 sieves: 450, 650, and 1000 μm. A wet-sifting technique was performed by rinsing
the set of sieves under a running faucet of deionised water, in order to remove better
the urea-formaldehyde debris. The collected microcapsules were then dried at room
temperature for approximately 24 hr as in Figure 1.
Figure 1. Microcapsules after sieve filtration.