Synthesis Of Polypropylene Composites Filled With Calcium Sulfate Whisker Prepared By Shale Vanadium Neutralizing Slag

The shale vanadium neutralization slag is a solid waste produced by vanadium shale acid leaching in the neutralization process,with good whiteness,high activity and less impurity content.After blending with acid leaching residue,the accumulation or landfill not only pollutes the environment but also wastes the resources.Through the analysis on the characteristics of the shale vanadium slag,it is used to prepare calcium sulfate whisker and modified to synthesis polypropylene composites,which can be harmless comprehensive utilized,and broaden the sources of raw materials of calcium sulfate whisker,reduce production cost of the composites.In this study,the preparation of calcium sulfate whisker and the suitable process for stability modification were first investigated,and the filler of calcium sulfate whisker suitable for filling polypropylene was obtained.Then,the performance and microstructure of polypropylene composites filled with calcium sulfate whiskers and neutralized slag were analyzed,and the influence mechanism of neutralization slag whiskerization and surface modification to the properties of composites was explored.The main conclusions were as follows:(1)The main component of shale vanadium neutralization slag was Ca SO4·0.5H2 O and a small amount of Ca SO4,which is a typical calcareous waste.The particle size is fine and the processing property is good.It is a suitable raw material for the preparation of calcium sulfate whisker.(2)The best technological parameters for preparing calcium sulfate whiskers by neutralization slag hydrothermal method are: the reaction temperature is 130 degrees,the reaction time is 6 h,the slurry mass fraction is 3%,and the auxiliary agent Mg Cl2·6H2O amount is 10 wt%.The optimum parameters of stearic acid modified whisker are as follows: stearic acid is 4 wt%,initial slurry concentration is 8 wt%,modified temperature is 90 C,and modification time is 20 min.Stearic acid inhibits the hydration of whiskers by blocking its hydrophilic active sites by chemical links with the whisker surface.(3)Under the same filling content,the order of the mechanical properties of the composites is: MCSW/PP > MHCSW > MNS/PP > NS/PP.When the filling amount is10%,the tensile strength,Young's modulus,flexural strength and flexural modulus of MCSW/PP composites are 37.3 MPa,570 MPa,42.8 MPa and 1100 MPa,respectively,which increase 10.4%,21.3%,30.2% and 49.9% compared with pure PP.The filling of inorganic filler can slow down the oxidation and decomposition of PP,inhibit the movement of the molecular chain,and improve the thermal stability and mechanical properties of the composite.(4)The interfacial debonding between the neutralizing slag and the substrate can alleviate the stress concentration and improve the mechanical properties.At the same time,the filling of neutralized slag has a heterogeneous nucleation effect on the polypropylene.The calcium sulfate whisker have stronger interfacial debonding and heterogeneous nucleation ability than neutralization slag particles,which result in better performance.But the rigidity effect is greater than the toughening effect,and the toughness of the composite will be reduced.