关键词: 羟丙基甲基纤维素, 表面张力, 接触角

Abstract:

The dynamic contact angle of hydroxypropyl methylcellulose (HPMC) powders on water surface,as wellas the air- water and the oil- water surface tensions of HPMC aqueous solution,were investigated at different concen-trations and pH values.The results show that (1) the wettability of HPMC powders is not strong enough and isslightly affected by the pH value; (2) the contact angle reaches its minimum 86.380° at pH 4.00; (3) the sur-face tension of HPMC aqueous solution mainly depends on the change of molecular chain conformation in the inter-facial area and varies with both the pH value and the concentration; (4) the air- water surface tension increaseswith the pH value at the mass concentration of 0.1% and shows a V- shaped variation with the pH value at the massconcentration ranging from 0.3% to 1.0%,which illustrates the complex change of HPMC molecular chain confor-mation in the interfacial area; (5) the conformation of HPMC molecular chains becomes more complex at the oil-water interface due to the interaction between HPMC and the lipid in the oil; and (6) the oil- water surface tensiondecreases with the increase of pH value that is not less than 6.00,and varies irregularly due to the greater effect ofconcentration when the pH value is less than 6.00.

Key words: hydroxypropyl methylcellulose, surface tension, contact angle