สำนักราชบัณฑิตยสภา

101 Jaruwan Krongsin, Roongkan Nuisin, Supaporn Noppakundilograt, Suda Kiatkamjornwong วารสารราชบัณฑิตยสถาน ปีที่ ๓๗ ฉบับที่ ๔ ต.ค.-ธ.ค. ๒๕๕๕ methosulfate, ceteareth-20, that has the higher paste consistency. The flow curves of the leave-on conditioner exhibited the lower viscosity and larger thixotropic loop which may be caused by the effect of chitosan/menthol emulsion. The formulations of the microcapsules containing a large amount of water tend to produce a fluid-like emulsion system that is prone to deform easily under high shear rates than that of the viscous system of a conditioner base. As such, one can observe a larger hysteresis loop of the conditioner base in both the shear stress vs. shear rate and viscosity vs. shear rate. 16,17 Accordingly, one can observe the much larger hysteresis loops of the leave-on conditioner in Figure 2 (c) having a flow area of 15.54 Pa as shown in Table II. It seems to be caused by the dilution effect of the chitosan/menthol microcapsule emulsion in Figure 2 (a) on the conditioner base in Figure 2 (b). When mixing the microcapsule emulsion with the conditioner base, an immiscible composite of leave-on hair conditioner can be expected. At zero shear, the microcapsules had a spherical shape, when it is subjected to a high shear rate, the microcapsules and other particulate molecules were elongated, deformed and broken when passing through a small tubing or slot. When the shear rate was removed or decreased, the molecules relaxed, reformed and restructured to increase their shear stress or viscosity. With the given time frame (not long enough for relaxation time), the downward hysteresis curve could not fully recover to meet the upward hysteresis curve. 15 Based on the observed thixotropic behavior of the three materials, the leave-on conditioner can fully recover its viscosity when a rest time was long enough. Therefore, before using the leave-on conditioner, one needs to break the thixotropic structure by shaking the bottle slightly to make it flow or become more fluidity.