| With the improvement of living standards, the safety of washing products had become more and more important for people. Traditional surfactants were made by oil and natural oil, however, the possibility of oil depletion and high prices exists, which forces people to find new sources of raw materials. Polymer surfactant made by starch has feature of non-toxic, non-polluting, bio-degradation. It was widely used in food industry, agriculture, detergents, cosmetics and other fields, is an important direction of surfactant industry.In this paper, regarding cassava starch as raw material, surfactant with special surface properties was prepared by physical, chemical methods. The structure and properties of products were characterized by using various analytical tools.The cassava starches were made by mechanical milling. The changes of starch structure and properties were studied. The results showed that surface structur made rough, cracks and debris appeared, crystal structure was destroyed, lattice size became smaller, even disappeared. The size of starch became smaller, surface area increased. The number of free hydroxyl increased, reactivity increased. The solubility increased, paste viscosity reduced, and viscosity stability increased with long milling time.Oxidized starch was preppared by cassava starch and oxidant under catalytic conditions. The carboxyl content as criterion, the optimum conditions were: CuSO4·5H2O as catalyst, reaction time 1.5h, temperature 40℃, dosage of oxidant 10% dry starh, catalyst 0.1% dry starch, pH=9. Under these conditions, oxidized starch with 0.24 carboxyl content is made. Structures and properities are studied. The results showed that the surface of oxidized starch appeared shades of dents and defects. Starches were degraded into many fragments, sticking together as larger degree of oxidation. The oxidized starch had the same crystal structure as cassava starch. In addition, the higher carboxyl content, the higher the transparency of liquid paste, the lower the analysis of water rate, the weaker the retrogradation, the better the freeze-thaw stability.The oxidized starch reacted with DDSA. DDSA content on the impact of DS was studied. Structure and properties were also studied. The results showed that the different carboxyl content of oxidized starch had different DDSA dosage to make high DS of SSDS. Infrared spectrum showed that a new peak appeared at 1566 cm-1 wavenumber, it standed for the characteristic absorption peak of C=C which proved SSDS was made successfully. SSDS had the same crystal structure as oxidized starch. The higher DS, the more serious damage to the surface of starch, the higher transparency of liquid paste, the weaker retrogration, the lower the surface tension, the lowest was 31.408mN/m . The rescults of complexing with APG showed the surface tension could reach the APG's standards, but surface activity was lower.The multiple modifications of cassava starch were studied. The performances of surfactants were studied. The rescults showed that amphoteric surfactants had lower surface tension, LX48's was 26.347 mN/m and MLX3's was 27.515 mN/m. They were lower by 8.2% and 4.1% than APG respectively. After complexing with APG, the surface tension decreased to 26.123 mN/m and 27.067 mN/m, their EC were 87.3 and 90.1 respectively, and the surfactants were optimum.
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