| Summary: | 碩士 === 國立臺北科技大學 === 有機高分子研究所 === 93 === In this work the unsteady-state contact angle at the interface between polymer melt and nano-titanium dioxide （photocatalyst） was measured. The transition of contact angle from an unsteady to a steady state when the polymer was melt can be divided into three stages, the unsteady thermo-stage, the wetting stage, and the reach of equilibrium contact angle .Subsequently, there are three critical indices, the unsteady heat-transfer period to, the retardation timeτ, and the contact angle at equilibrium state A∞ are defined herein. The decrease in contact angle against time can be simulate by an exponential decay that involves these three critical indices. Molten polystyrene（PS）has the smallest equilibrium contact angle A∞ , polymethyl methacrylate（PMMA）and high impact polystyrene（HIPS） have the greatest angle. Interestingly , this order is strongly related to the solubility parameter of each polymer. The equilibrium contact angle A∞ is effected by the viscosity of the melt polymer. The equilibrium contact angle A∞ will decrease when we increase the melt temperature. The smooth surface of nano-titanium dioxide has the shorter retardation timeτ，but has higher equilibrium contact angle A∞. Ther higher density of nano-titanium dioxide has longer retardation timeτ，but has lower equilibrium contact angle A∞.
Mixing experimental results are that the HIPS has higer torque(11.5 Nm) than PS(9.5 Nm), but the PS has longer retardation timeτ(417 sec) than HIPS(400 sec). We change the adding time of nano-titanium dioxide , the torque of mixer is same. We can change the adding time of nano-titanium dioxide according to the mixing machine.
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