To investigate the dyeing Mechanism of the sunning process, the chemical constructive changes of dioscorea cirrhosa tannin and fibers before and after processing were analyzed by high-performance liquid chromatography (HPLC) and infrared spectroscopy (IR). According to the test results and plant polyphenols chemical theory, this study reached the following conclusions. Firstly, during the sunning process, the dioscorea cirrhosa tannin is oxidized and converted to quinoid structure by solarization. With the deepening of the process, the surface color of the fabric gets darker, eventually becomes brown or brownish red. Secondly, the multipoint combination of hydrophobic bond and hydrogen bond may be the common mode which dioscorea cirrhosa tannin is combined with silk, cotton and hemp fiber. The number of combination sites and the bonding strength vary greatly with the difference of fibers’ chemical structure, thus affecting dyeing fastness. There are hydrophobic amino acids and many combining sites for hydrogen bonding in silk structure, so a large number of hydrophobic bonding and hydrogen bonding can be formed, and a better processing effect can be obtained. Thirdly, the other two possible factors contributing to silk’s good processing effect are, respectively, the covalent bonds between tannin and silk, and the richness of silk’s fibrillar structure, which significantly increase the binding points between silk with tannin, compared with the other fibers.
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