| Polymer coated steel strip is a new type of functional metal and polymer composite material,which has better safety,environmental protection,aesthetics,and molding processing and packaging protection and preservation performance.It is in line with the development trend of energy saving,material saving,green environmental protection,and high taste in the metal packaging industry.Therefore,it has been valued since its invention and has been recognized as a future product to replace TFS(tin free steel)packaging materials.This article was funded by the National Natural Science Foundation of China.Facing the urgent needs of domestic polymer coated steel preparation theory and technology,focusing on the serious problems of domestic polymer coated steel enterprises in terms of production efficiency and product quality.Aiming at the bonding behavior between the metal substrate and the polymer film interface during the melt coating process of polymer coated steel,as well as the influencing factors and laws of the coating process and quality,a multi-scale method was used to combine experiments,numerical simulations.and theoretical analysis.system Research.The research is based on the polymer coated steel production line of a large domestic enterprise,and the research results provide theoretical guidance for the enterprise to solve production technical problems.The main research content and results of the thesis are as follows.(1)In view of the compound process and behavior law between the polymer film polyethylene terephthalate(PET)and the hydrated chromium oxide on the surface of TFS in the molten state of the polymer coated steel coating process,first pass the X-ray photoelectronspectroscopy(XPS)experiment characterizes and analyzes the chemical composition of the hydrated chromium oxide layer on the surface of the chromium-plated steel strip.It is determined that the hydrated chromium oxide layer is composed of chromium oxide,chromium hydroxide,and chromium oxyhydroxide molecules;then molecular dynamics combined with first-principles methods are used The combination model of PET molecules and chromium oxide molecules at the microscopic scale,and the combination models of chromium oxide molecules with different hydroxyl concentrations and PET molecules were established.The results show that chromium oxide molecules and PET molecules are combined in the form of Lewis acid-base interactions,and the binding energies of the binding models corresponding to Cr2O3(110),Cr2O3(200),and Cr2O3(211)crystal planes are-13.07eV,-2.74eV and-2.37eV;hydroxylated chromium oxide molecules and PET molecules are combined in the form of hydrogen bonds,and the combination of the two is linearly positively correlated with the concentration of hydroxyl groups on the surface of chromium oxide,which improves the hydrated chromium oxide layer on the surface of chromium-plated steel The concentration of hydroxyl in the polymer can effectively improve the bonding strength of the polymer coated steel interface.(2)In the preparation process of polymer coated steel,the chrome-plated steel strip and PET film are heated by the heating roller and the temperature of the laminating roller is cooled by the complex temperature control process,the temperature change of the substrate and the film,and the heat transfer behavior of each interface during the laminating process.According to the law,an integrated numerical simulation model of laminating roller-PET-chrome-plated steel-heating roller is established,which reveals the recrystallization behavior of the PET film on the surface of the chrome-plated steel after being heated during the melting and laminating process.And the law,the law of the internal temperature change of the PET film during the melt coating process and the law of the impact of the process parameters of the film on its temperature change,and the law of the melt thickness of the PET film during the melt coating process and influencing factors.The results show that the increase of the pressure of the laminating roll makes the contact arc length of the PET and the chromium-plated steel interface longer.Under the condition of a certain laminating speed,the interface contact heat transfer time is increased;the laminating speed affects the thickness of the film melting layer,which is too large The film coating process speed will cause the polymer coated steel film to melt completely;the increase of the initial preheating temperature of the film roll and the strip will make the melting layer thicker,and the initial preheat temperature of the oversized film roll and strip will also The polymer coated steel film is completely melted;the film speed and the initial preheating temperature of the film roll and the substrate strip are the main process parameters that determine the thickness of the film melting layer.(3)Aiming at the melting,flow and filling behavior of the molten PET film on the rough surface of the chromium-plated steel strip during the melting and coating of polymer coated steel,simulation experiments combined with finite element numerical simulation are used to reveal the melting and coating process The influence of the surface profile of the chromium-plated steel strip of the medium substrate on the bonding behavior of the bonding interface of polymer coated steel.The results show that with the increase of the coating temperature,the bonding rate and bonding strength of the polymer coated steel interface gradually increase;with the decrease of the coating speed,the bonding rate and bonding strength gradually increase;the surface temperature of the chromium-plated steel strip of the base material is not Both will cause bubbles to appear in the finished polymer coated steel film.(4)Aiming at the quality problem of uneven thickness of PET film on the surface of the finished polymer coated steel due to various reasons such as raw material conditions,process conditions and equipment accuracy during the laminating process,the finite element simulation method was used to carry out the laminating process.Mechanical modeling and analysis reveal its main influencing factors and their influence rules.The results show that the lateral temperature difference on the surface of the chrome-plated steel strip has a major influence on the lateral melting thickness of the PET film on the polymer coated steel surface.Increasing the surface temperature of the chrome-plated steel can reduce the influence of the lateral temperature difference on the lateral melting thickness difference of the PET;The longitudinal thickness of the PET film on the surface of the polymer coated steel and the longitudinal melting thickness are negatively correlated;the influence of the eccentricity of the laminating roller on the longitudinal thickness of the PET is gradually attenuating;the increase of the thickness of the silicone layer and the decrease of the hardness of the silicone layer can reduce the laminating roller The effect of eccentricity on PET longitudinal thickness difference. |
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