Study On Microstructure And Cationic Modification Of FAFs

FAF is a new type of inorganic fiber which came out in recent years, whose application used in paper making is just staying in the level of learning from the experience of glass fiber, as FAFs are not been researched deeply in China and abroad. The primary problem encountered in paper making is FAFs'bad dispersion in water, which would seriously affect the quality of paper produced. The purpose of the paper research is to find appropriate modification method which could improve FAFs'dispersion in water and have a study on the relationship of Zeta potential and dispersion performance. This paper research would have a certain significance for pushing the development of FAFs used in paper making and providing strong protection for fly ash's utilization.FAFs were studied systematically through a series of characterization means such as XRD, XRF, Solid-NMR, IR and so on. Backbone structure of Si-O and Al-O, surface groups and electrical properties were focused on especially. Leaching process in acid or alkali solution were researched through EDS and ICP analysing methods. The appropriate pretreatment conditions were fixed. Have cationic modification on FAFs respectively. Study on the dispersion mechanism for FAFs in water. Results were gotten as below:1. The FAFs' surface were very smooth and there were few active groups on them, which was not beneficial for surface modification. FAFs belonged to inverse glass structure, which meant that there was no crystal phase. Only 33.8% of silicon-oxygen tetrahedron were at the state of three-dimensional network, the others were all Q1(1Al), which was absolutely opposite with glass fibers'structure of irregular network theory.2. In normal temperature, FAFs was alkali-resistant and easily eroded in acid. The mean length decreased and the content of -OH increased after leaching in acid solution. A new layer of fiber surface would expose after hydrochloric acid leaching; The H2PO4 would have nucleophic substitution with≡Al-OH on the surface of FAFs and then aluminum phosphate layer generated after phosphoric acid leaching.3. Have process optimization on the two methods of cationic modification through orthogonal experiments. FAFs modified by cationic starch had good dispersion performance in water through analysis by settling experiments and contrast optical microscope images. The dispersion method suit to glass fibers could not be used on the dispersion of FAFs. Through study on FAFs'dispersion mechanism in water, the reason why FAFs were easily entangled with each other in water was that there were so many weak acid points and alkali points on the surface that they were attracted by static electricity. Cationic modification could improve the performance of dispersion of the FAFs in water. The dispersion and settling experiments proved that the higher the surface Zeta potential was, the longer the settling time would be and the better the dispersion performance would turn.