Insitu Microwave-Assisted Functional Finishing Of Cotton Fabric Using Nano-Zinc Phosphate

Microwave method has become a research point in functional finishing of cellulose fabrics and material synthesis due to its advantages such as heating the reaction system rapidly, accelerating the reaction and shorting the reaction time. In this paper, UV-blocking and flame retardant cotton fabric were obtained by microwave method and traditional pad-dry-cure method, using cheap industrial products zinc nitrate, sodium dihydrogen phosphate and urea as raw materials.The synthesis of zinc phosphate was first investigated and characterized by IR, XRD, TG-DTG. Then number of crystal water of zinc phosphate was studied under different drying temperature. The results showed that the sol powder under80℃drying condition was Zn3(PO4)2·4H2O and under150℃was Zn3(PO4)2·2H2O, while the sol product under140℃was a mixture of Zn3(PO4)2·4H2O and Zn3(PO4)2·2H2O. In addition, it was found that the sol of zinc phosphate showed a strong UV absorption, as a result, the zinc phosphate can impart the fabric with excellent ultraviolet resistance.UV-blocking cotton fabric was obtained by microwave-assisted in situ synthesis of zinc phosphate. It was found that in the UV-blocking finish treatment the UPF value of the pure cotton fabric was8.12, the UPF value of the finished cotton fabric increased with the increase of the concentration of zinc nitrate. When the concentration of the zinc nitrate was0.5mol/L, the UPF value of finished cotton fabric was98. The UPF value of finished cotton fabric also increased with the increase of curing temperature and time. The curing temperature and time had a significant influence on the UPF values while the microwave temperature and time had a little effect on the UV-resistance capabilities of the fabric.UV-blocking and flame retardant finished cotton fabric with flame retardant and UV-blocking capabilities was prepared by microwave-assisted in situ synthesis of zinc phosphate and conventional pad-dry-cure finishing process. It was found that the finished cotton fabric treated with zinc phosphate and urea showed very excellent flame retardancy. The LOI value of the finished cotton fabric can reach to28.9. However, the cotton treated only with zinc phosphate or urea didn’t show good non-flammability. In TG-DTG test, the onset temperature of treated cotton fabric reduced to20.4℃and the max decomposition reduced from20.50%/min to8.61%/min. The flame retardant capability increased with the increase of concentration of zinc nitrate under a certain concentration of urea. However, under the certain concentration of zinc nitrate, the LOI of treated cotton fabric firstly increased and then reduced with the increasing concentration of urea. This result showed that there was a phosphorus-nitrogen (P-N) synergistic action in the flame retardancy of cellulosic fibers. The best synergistic flame retardant ability can be achieved only under a certain ratio of zinc phosphate and urea.SEM analysis was investigated to observe the morphology change of zinc phosphate on the cotton fabric before and after burning test. SEM analysis showed that the surface of pure cotton fabric fiber was smooth and had a certain degree of natural curvature. After burning, the cotton fabric fiber became hollow and the structure of the fabric became very loose. and some zinc phosphate particles dispersed on the fiber surface clearly covered by a thin film. After the burning test, a flame retardant thin film formed on the cotton fiber surface and the structure of the cotton fabric almost didn’t change. This could be due to the new substance produce in the burning processing by zinc phosphate and urea on the cotton fabric improved the flammability of cotton fabric. The SEM of UV-blocking cotton fabric (only with zinc phosphate) showed that zinc phosphate dispersed on the cotton fiber in the condition of bulk or plate-shape particles.