Preparation And Application Of Vanadium Tailing Filler In Polypropylene

With the development of vanadium industry in China,the output of vanadium tailing?VT?is enormous.Since there are still many heavy metal elements in VT,a large number of VT treated by stacking or landfill will not only occupied the land,but also may cause secondary pollution to the environment.After fine grinding,roasting and leaching,the particle size of VT is fine and the mineral structure is effectively destroyed.A lot of quartz and gypsum in VT is beneficial for it to be acted as mineral filler for polymer.The inorganic filler made by VT can broaden the source of filler and reduce the cost of polymer production.Moreover,the effective use of VT and curing of heavy metal elements are good to environmental.Based on the analysis of the properties of VT,a suitable method for preparing polymer filler with VT was studied in this paper.First of all,the superfine processing of VT was investigated,and the suitable grinding aids and grinding process for VT were determined in this study.Then the effects of different kinds of coupling agents on the surface modification of VT were investigated to determine the optimum modification process.The suitable inorganic filler for polypropylene?PP?which prepared by modified VT?MVT?was obtained.Finally,the mechanical properties and microstructure of the composites filled with VT or MVT were studied.The mechanism of MVT and coupling agent on the polypropylene matrix were investigated.And the curing effect of polypropylene on the heavy metals in VT was also discussed.The main conclusions are as follows:?1?The main chemical composition of VT are SiO2 and CaO.The particle size of VT is fine,the mineral structure is destroyed and the particle surface is rough.There is a large number of high reactivity hydroxyl on the surface of VT and the heat stability is excellent.So it is suitable for VT to use as a polymer filler.?2?Sodium pyrophosphate is a suitable grinding aid for VT in wet superfine processing.When the content of sodium pyrophosphate is 1.8 wt%,the time required for the ultrafine grinding product of VT to reach the same particle size is shortened comparing with that without grinding aid.The optimum technological parameters of modification by DL-411 coupling agent are as follow:the content is 1.2 wt%and modified temperature is 100°C.The activity index and oil absorption of MVT powder are 95.53%and 30.76 ml/100g,respectively.?3?Used DL-411 for modification of VT in the best process conditions.The particle size of MVT used for the preparation of composite with optimum comprehensive mechanical properties is D₉₀=12.64?m,while the content of MVT is20 phr.The tensile strength,flexural strength and flexural modulus of the composites are 50.66 MPa,57.23 MPa and 1706.92 MPa respectively,which are 16.25%,22.58%and 46.63%higher than those of pure PP respectively.Only the impact strength decreased by 1.39%to 41.78 kJ/m².The thermal stability of composites are improved by filled with MVT.The PP matrix in composites encapsulates VT particles,making the heavy metals more difficult to be leached.So the heavy metals in VT can be cured effectively.?4?VT has a heterogeneous nucleation effect on PP and coupling agent enhance the nucleation effect.The MVT particles improve the mechanical properties of the composites by occurred an interface debonding phenomenon with PP matrix.But the MVT particles are rigid and can not be deformed,causing the particles to separate from the matrix and the toughness of the material decrease.