Study On Dispersion Of Calcium Carbonate Filler In Polypropylene Thought Fluorescence-LSCM Technology

In polymer composites,the uniformity dispersion of inorganic filler plays a key role in the mechanical strength,electrical conductivity,dielectric constant,heat transfer,and abrasion resistance of polymer composites.At present,researchers have conducted in-depth discussions on methods to improve the uniformity of filler dispersion.However,due to the lack of objective and universal index requirements for filler uniformity,it is difficult to quantify the dispersion state.This has an uncertain impact on the modification methods of inorganic fillers and the choice of polymer composite formulations.In order to scientifically analyze the evolution of filler dispersion uniformity in polymer composites and its effect on mechanical properties,it is of great practical significance to develop a quantifiable simple and practical method for detecting filler dispersion uniformity.In this paper,self-made calcium carbonate microspheres and commercially available light calcium carbonate were fluorescently labeled with fluorescent labeling technology.Polypropylene-based composite materials were prepared using polymer composite processing technology,and the dispersion state of calcium carbonate in polypropylene was studied by combining LSCM and fractal analysis theory.The purpose is to explore the quantitative description of the calcium carbonate filler dispersion state in polypropylene-based composites and its relationship with the macro mechanical properties of composites.The main conclusions are as follows:（1）Two kinds of calcium carbonate fluorescent microspheres,CaCO₃@SiO₂:Eu（DBM）₃phen（CSF-CaCO₃）and CaCO₃@Eu（DBM-Si）₃（F-CaCO₃）,were prepared by physical coating and chemical grafting respectively,The surface structure and fluorescent properties of two fluorescent calcium carbonate microspheres were studied.The results show that the two fluorescent calcium carbonate microspheres have uniform surface fluorescence distribution,broad excitation band,and can emit the characteristic red emission peak of rare earth Eu³⁺at about 610 nm.The three-dimensional visualization of the fillers in the polypropylene matrix was realized.Comparing the reconstruction results,it was found that the reconstruction results of F-CaCO₃ were higher in sphericity,better mono-dispersity,and closer to the real situation.（2）The fractal states of F-CaCO₃ in F-CaCO₃/PP composite with different filling amount（2²0 wt.%）were studied thought fluorescence LSCM technology and fractal analysis theory.The results show that with the increase of F-CaCO₃ filling amount,the fractal dimension D value first decreases to 1.81,and then increases,the dispersion state of the filler correspondingly becomes uniform,and then the uniformity becomes worse with the increase of fractal dimension D value.Therefore,the fractal dimension D value based on fluorescence LSCM technology and fractal analysis theory can quantitatively describe the dispersion uniformity of fillers in composite materials.（3）On the basis of fluorescent labeling,the commercially available light calcium carbonate was modified with sodium stearate to obtain a modified fluorescent light calcium carbonate MF-CaCO₃ with better hydrophobicity.The maximum contact angle was 146.4°and the average particle size decreased from 2.3μm to 1.2μm through the contact angle,fluorescence and other performance tests,the results show that the surface energy of MF-CaCO₃ decreases,the binding force between powders weakens,and the dispersion effect of powders becomes better.When the amount of sodium stearate is 3 wt.%,the fluorescence intensity of the modified fluorescent calcium carbonate increases by 113.54%,which shows that the appropriate amount of sodium stearate can sensitize and enhance the fluorescence performance of Eu³⁺.（4）Based on fluorescence-LSCM technology,fractal analysis theory and mechanical property test,the relationship between the dispersion state and impact property of MF-CaCO₃with different filling amount（2²0 wt.%）in MF-CaCO₃/PP composite were studied.The results show that MF-CaCO₃ can improve the impact properties of the composites,and the maximum impact strength is 14.91 KJ/m² when the content of MF-CaCO₃ is 15 wt.%;The fractal dimension D value is used to describe the dispersion uniformity of the samples respectively.When the MF-CaCO₃ filling amount is 15 wt.%,the minimum fractal dimension D value is 1.91,and the dispersion of the filler is the most uniform,and the corresponding impact performance is the largest.The impact performance of the composite is negatively correlated with the fractal dimension D value.This shows that the mechanical properties of the composite can be improved to the greatest extent by improving the dispersion uniformity of the filler in the composite.The uniform distribution of the filler in the matrix has a specific value,and the insufficient or excessive distribution cannot reach the optimal state.When the dispersion state of the filler reaches absolute uniformity,the filler in the composite can play a macro effect of maximum transfer and low efficiency of external energy,and finally can produce the reinforcement and toughening effect on the composite.