Numerical Simulation And Experimental Verification Of The Mechanical And Compatibility Of PP/PET Composite Materials Compatibilized With CNTs

Polypropylene(PP)and polyethylene terephthalate(PET)are common materials for polymer modification.PET can enhance the heat resistance and modulus of PP,and PP can enhance the processability of PET and reduce its sensitivity to water.However,PP/PET blends have high interfacial tension and poor compatibility,and their application is greatly limited.Carbon nanotubes(CNTs)have high aspect ratio and excellent mechanical properties.It is of great significance to mix CNTs with PP/PET composites to prepare composites with good processability.The attention of CNTs at home and abroad is mostly on the mechanical properties,and the compatibilization of CNTs as interface transition phase is rarely studied.The addition of CNTs to PP/PET composites has an impact on the mechanical properties and compatibility of the materials and broadens their application fields.This article simulates the mechanical properties and glass transition temperature(Tg)of pure PP models and composite models with different PET ratios(10%,15%,25%)based on molecular dynamics.It is found that the stiffness coefficient,bulk modulus,shear modulus,and Young’s modulus of PP/PET composite systems with different ratios increase compared to pure PP systems,while the flexibility coefficient decreases.Among them,the mechanical properties of PP/PET(85:15)composite systems are more prominent.Construct CNTs/PP/PET composite crystal cells with better mechanical properties,simulate their mechanical properties and Tg,and analyze that the mechanical properties of CNTs/PP/PET composite system have been improved,and CNTs make the two Tg of PP/PET composite system closer,and the compatibility has been improved to some extent.CNTs/PP/PET composites with different mass ratios of 0wt%,1wt%and 2wt%were prepared by melt blending and injection molding with CNTs,PP and PET as raw materials.Through scanning electron microscope observation,CNTs can reduce the size and number of "sea-island structure" and pits on the fracture surface of PP/PET composite,which proves that CNTs play a certain role in compatibilization.Through tensile test,it was found that the tensile strength of CNTs/PP/PET composites increased and the elongation at break decreased with the increase of CNTs content.The XRD diffraction analysis shows that the absorption peak of PP is obvious,and carbon nanotubes can enhance the diffraction effect of the material on the(110)and(040)crystal planes,and PET can inhibit α crystallization of monoclinic PP.According to Vickers hardness tester,the hardness of CNTs/PP/PET composites increases with the increase of CNTs content.According to the rheometer,when the test temperature is 230℃,the storage modulus of CNTs/PP/PET composites increases with the increase of CNTs content.The loss modulus of CNTs/PP/PET composites with different CNTs content is significantly higher than that of pure PP.As the frequency increases,the complex viscosity of CNTs/PP/PET composites(η*)decrease.