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Preparation and Assessment of Chitosan Encapsulated Menthol Microcapsules for Leave-on Conditioners 98 The Journal of the Royal Institute of Thailand Vol. 37 No. 4 Oct-Dec 2012 Table I Composition of leave-on conditioners Components Function Amount (%) Chitosan microcapsules Control released 72.0 microcapsules Deionized water media 22.5 Cetearyl alcohol Dipalmitoylethyl 5.0 hydroxyethylmonium Conditioner base methosulfate Ceteareth-20 Glydant Preservative 0.5 Hair treatment with the leave-on hair conditioner The virgin Asian hairs (2.5 g) were repeatedly cleaned using a 1.25 cm 3 solution containing 14% w/w solution of sodium dodecyl sulfate at room temperature. Then, 0.025 g of the leave-on conditioners was applied onto 0.5 g cleaned hairs and the hairs were air dried at room temperature prior to further analyses. Characterization Flow property of the leave-on conditioners by viscosity The viscosity of chitosan/menthol emulsion, conditioner base and leave-on conditioner was determined by Brookfield viscometer (model LVDV-III Ultra equipped with a needle-shaped no. 64 spindle, U.S.A.). The chitosan/menthol microcapsules (10 cm 3 ) was transferred to a small sample holder and covered with a lid to prevent water evaporation during the measurement. For the viscosity measurement, the shear rate was scanned from zero shear (0 s -1 ) to 25.9 s -1 while the sample temperature was controlled at 25 º C . For the leave-on conditioner, 25 cm 3 of the conditioner paste was transferred to the sample holder and measured by the same method described above.