Research On Preparation Of Polymer Filler From Bauxite Tailings

Bauxite tailing is a kind of industrial solid waste, which results from the development of Al industry. It restricts the sustainable development of mining, occupys farmland and pollutes environment. Tailing contains a few metal impurities. Its main mineral structure is the same as layered aluminous silicate mineral which is .used as plastic filler. It has a broad market prospect.The main chemical components of tailing are aluminum oxide (Al₂O₃) and silicon oxide(SiO₂), of which the content is as high as 70%. The main mineral phase of tailing includes diaspore and kaolin which take up as much as 50%. Tailing is easy for ultra-fine processing because of its small size (d₉₀≤65μm). The main study makes use of ore pulp as raw material. It is adopted both wet and dry ultra-fine processing in order to obtain excellent grinding technology. The size of tailing powder is homogeneous (d₉₀≤10μm); its morphology is near-spherical. It has stable chemical properties, good thermal stability and fire-resistant. It can meet the requirements of plastic filler.The surface modification of tailing is respectively treated by titanic ester coupling agent, saline coupling agent, silicone oil and quaternary ammonium salt, which testifies that the content of different coupling agent exists an optimal range. According to analysis and comparison, titanic ester coupling agent and saline coupling agent were selected to modify composite, of which the effect of modification is good. Activation index is more than 90%; contact angle is as high as 130°; oil absorption is less than 14 ml/100g. The results show that the modification changes the polarity of the surface of tailing powder, which changes from hydrophilic to hydrophobic. Modified tailing powder is mostly in oligomic state and the dispersion degree is improved. In order to discuss modification mechanism, the unmodified and modified tailing powder are studied by IR. The bond at 2959.71cm^-1 indicates the chemical band function between coupling agents and powder surface. Modified tailing powder is studied by SEM and EDAX, which show that the different mineral phase of tailing has selectivity to adsorb modifier, i.e., diaspore adsorbs NDZ, and kaolin adsorbs KH.The best modified powder is added as filler in polyvinyl chloride (PVC) matrix to produce PVC composite by melt extrude. The physical, mechanical and thermal properties of PVC composite are studied. The results as follows: the filler has multi-component affection; the rigid and heat-resistant of filled PVC composite are improved. PVC composite owns well flow and process properties when the filler content is 40Phr; the coupling agents have plasticizing and lubricative effect; modified filler can be distributed uniformly in the PVC matrix, which finally determines the higher properties of the PVC composite: izod notched impact strength is 7.8kJ/m²; tensile strength is 33.8MPa; break extensibility is 17%; vicat malacia temperature is 86.1℃. Break appearance is studied by SEM, which shows that the filler has nucleation effect, indicating a better compatibility between PVC and filler and stable associated interface. Properties of PVC composite meet the standard of enterprise. The study is important for increasing the added value of tailing, developing new material and protecting environment.