| Fire-retardant coating is a kind of functional coating that has the capabilities of both decoration and flame-retardancy. In this paper, the inexpensive and renewable soy flour (SF) was used as the raw material. The soybean protein was modified and the appropriate additives and fillers were added. Then, the preparation of environmental friendly and excellent waterborne flame-retardant coating was studied, The main contents of study were investigated as follows:Study on modification of soy flour. Soybean protein flour was modified by alkali, and the influences of concentration, alkali dosage, reaction temperature and time on viscosity of the modified soybean protein solution were studied. The crystallinity and protein secondary structure of the modified soybean protein were characterized by XRD and IR spectrum, respectively. The experimental results showed that when the alkali dosage was 4%(based on the mass of soy flour), reaction temperature was 60℃ and the time was 0.5 h, the modified soy protein achieved the best modification effect. At this moment, the viscosity of the modified soybean protein solution was the largest, the crystallinity of the modified soybean protein powder was destroyed, and the random coil content of protein secondary structure reached the highest. But the excessive alkali dosage, too high reaction temperature and too long time would cause the degradation of the soybean protein molecules.The pH of the alkali-modified soybean protein solution was adjusted by acid, and the influences of alkali-modified soy protein were studied by UV spectrum, microscopy and the change of protein secondary structure. The results showed that, until 7 of pH, the basic structure of the soybean protein didn’t change, the protein secondary structure of the modified soybean protein changed slightly, the secondary reunion of soybean protein didn’t happen, and the color of emulsion was relatively light. Adjusting suitable pH of alkali-modified soybean protein solution can promote to form protein film.Study on the water absorption and dissolve-loss ratio of soybean protein film. The influencing factors of the water absorption and dissolve-loss ratio were studied, and the effect of adding metal ions and the feeding process on protein film were also studied. The experimental results showed that when the reaction temperature was 30℃, pH was 7 and the oven-dried temperature was 120℃, the water absorption and dissolve-loss ratio of soybean protein film was low. Under this condition, adding 1.0 g ZnCl2 before modifying the soybean protein could reduce the water absorption greatly, but it didn’t have an effect on dissolve-loss ratio.Study on the flame-retardant properties of coating. Firstly, Ammonium polyphosphate (APP) and Zinc borate (ZB) as flame retardants were prepared, and then their structures were identified by IR and XRD spectrum, their thermal stability were analyzed by TG-DSC. Finally, the different types of flame retardants were added in the modified soybean protein emulsion. And then, the flame retardant properties were tested. The results showed that APP and ZB had the excellent thermal stability. In all flame retardants, P-N flame retardants could inhibit the ignition effectively. B-Zn flame retardants had a favorable flame-retardancy. Complex of flame retardants, when APP:ZB was 3:1.2, the coating had the optimal flame-retardant effect.Based on the above, the optimal formulations of fire-retardant coating were investigated. The results showed that added-16 g of titanium pigment,16 g of silicon dioxide,0.8 g of sodium hexametaphosphate, the amount of defoaming agent and pH adjusting agent, the resultant coating had good flame-retardant properties.It was showed that the modified-soybean-protein-based waterborne fire-retardant coating possessed the excellent flame-retardancy. It is functional and environmental, and accords with the way of the development of the coatings industry, and possess the good foreground of development and application. |
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