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Preparation and Assessment of Chitosan Encapsulated Menthol Microcapsules for Leave-on Conditioners 96 The Journal of the Royal Institute of Thailand Vol. 37 No. 4 Oct-Dec 2012 Reaction Setup A miniature kit for emulsification with an SPG module was purchased from Kiyomoto Co., Ltd (Japan). A tubular porous glass membrane with a length of 2 cm and 1 cm in diameter was installed in the module. The dispersed phase (an oil phase) was stored in a Teflon vessel (20 cm 3 ) which was connected to a nitrogen gas inlet, the continuous phase (an aqueous phase) containing a mixture of SDS and PVA in a 250-cm 3 beaker was stirred at 300 rpm with a magnetic bar to prevent creaming of the droplets. With an optimum pressure of nitrogen gas, the dispersed phase can permeate through the uniform pores of the membrane into the continuous phase to form emul- sion droplets. The droplets were then stabilized by the PVA and SDS dissolved in the continuous phase. Preparation of chitosan microcapsules and leave-on conditioners The preparation of oil-in-water emulsion of chitosan/menthol microcapsules were car - ried out via a double emulsion method. As mentioned above, the SPG emulsification was used for preparing the primary emulsion, while the high-speed disperser for the secondary emulsion. The final emulsion was obtained by mixing the primary and secondary emulsions. Preparation of primary emulsion and secondary emulsion The SPG membrane was pre-wetted in the aqueous phase. A pressure used was slightly above the critical pressure. The ranges of the permeation pressures from 14.1 to 67.0 kPa for the 5.2 µ m membrane pore size were applied to the membrane. Menthol was dissolved in a mixture of light mineral oil, and cetyl stearyl alcohol co-surfactant by heating up to 40-43 º C and was used as a dispersed phase. The aqueous phase containing 3.0 g PVA and 1.5 g SDS was dissolved in 200 cm 3 of deionized water. The oil phase permeated through the uniform pores of the SPG membrane by the predetermined pressure of nitrogen gas into the aqueous phase to form the o/w primary emulsion. The secondary emulsion was prepared via a high-speed disperser. The continuous phase was composed of 50.0 g of deionized water, 0.05 g of sodium dodecyl sulfate, and 10 cm 3 of 1% w/v chitosan solution in acetic acid (1% v/v). The oil phase consisting of 5.0 g of mineral oil, the emulsion was then mixed using a high-speed disperser at 14,000 rpm for 90 s. The emulsion was thereafter stirred continuously at 400 rpm to prevent the coagulation.