Ahmad Jamekhorshid

Microcapsules containing paraffin wax as cores and polystyrene as shells were prepared by suspension polymerization technique. The influence of four experimental factors, including percentage of initiator/ styrene mass ratio (BPO/St wt.%), paraffin wax/styrene mass ratio (PCM/St), percentage of stabilizer/ styrene mass ratio (PVP/St wt.%), and water/styrene mass ratio (H2O/St), on microcapsules properties were investigated. Each factor was in five levels. Response surface methodology (RSM) was implemented for statistical design and analysis of experiments and process modeling. Two mathematical models were derived for prediction of melting latent heat of microcapsules and their average particle size. Analysis of variance showed that PCM/St mass ratio was the most significant factor affecting melting latent heat of parameters, while average particle size is affected by PVP/St wt.% and H2O/St mass ratio. In process optimization, maximum values of melting latent heat were achieved as 148.5 J/g. Using BPO/St wt.% of 2.18%, PCM/St mass ratio of 1.94, PVP/St wt.% of 8.84%, and H2O/St mass ratio of 11.67, encapsulation ratio of 78.5% were obtained.