Effect of Acid-Base Treatment on Wettability and Mechanical Properties of Polyimide Membrane
Due to the poor polarity and poor adhesion of polyimide(PI)films,the comprehensive performance of PI films is limited.The effect of sodium hydroxide(NaOH)concentration on the surface and mechanical properties of PI films was studied.Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),atomic force microscopy(AFM)and static contact angle and dynamic contact angle analysis(DCAA)were used to analyze the surface chemical structure,surface morphology,surface roughness and surface wetting properties of PI films before and after acid and alkali treatment.The mechanical strength of polyimide films treated with different concentrations of NaOH was measured by tensile tester.The results show that the O/C ratio of PI film surface increases from 27.70％to 47.26％,and the surface energy increases from 27.65 mJ/m2 to 58.2 mJ/m2.The results of XPS show that the content of C-O active group on the surface of PI film increases,and the infiltration of PI film surface is increased.With the increase of the concentration of NaOH,the mechanical strength of the film decreases significantly,which is related to the hydrolysis of NaOH.
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