Study on Mixing Mechanism and Structural Properties of Polyester Composite System via Volume Pulsation Processing

Author:Qiu Feng

Supervisor:zuo jin ping

Database:Doctor

Degree Year:2019

Download:24

Pages:139

Size:10981K

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The different processing and molding methods of the polymer will form different microstructures,which directly affect the final structure and properties of the product,which indicates that the processing and molding methods play a key role in the quality of the polymer product.The traditional screw extruder processing equipment is based on the shear flow field during the plasticizing transport processing.It has a long mechanical history and a large shear force field,which has a certain destructive effect on the polymer molecular chain.However,independent development of eccentric rotor extruder equipment is based on volume elongation flow field of plasticizing transport during processing,owning shorter mechanical process,lower energy consumption,having better mixing dispersion and distribution and making less damage to polymer molecular chain,thus allowing polymer to maintain the character of itself originally.Therefore,based on the structural characteristics of the eccentric rotor extruder dominated by the elongation flow field and the characteristics of the polymer material,compared with the traditional screw extruder processing method.A comprehensive and in-depth study of the characteristics of the mixed dispersion distribution of polyester composite system and the effect of volume elongation deformation on the structural properties of polyester composite system under the volume pulsation plasticizing is of great significance to prepare the high performance polyester composites and promote the innovative development of polymer processing equipment.This paper introduces the structural characteristics of eccentric rotor extruder based on volume elongation flow field,and emphatically introduces that the core of eccentric rotor extruder is the extrusion system composed of eccentric rotor and stator,in which both rotor and stator have topological geometrical structure.When the rotor rotates,the material cavity between the rotor and the stator changes periodically along the axial and radial direction of the stator,so that the polymer is subjected to the volume elongation deformation force field during the periodic compression and expansion.The elongation deformation runs through the solid conveying zone,the melting zone and melt conveying zone along the whole melting plasticizing process.Through the sampling of polyethylene terephthalate/thermoplastic polyurethane blends in the process of volume pulsating plasticizing transport,the evolution process and mechanism of the blending morphology of polyester composite system under the volume elongation deformation were studied,and the scanning electron microscope,wide-angle X-ray diffraction and the differential scanning calorimeter to characterize the mixed dispersion distribution morphological characteristics and crystal morphological structure of the molten plasticizing transport sections respectively.It was found that under the volume elongation deformation,polybutylene terephthalate can complete the melting plasticizing process quickly,the particle size of thermoplastic polyurethane as a dispersed phase finally reached 0.6μm.In this paper,the eccentric rotor extruder based on volume elongation flow field is studied to prepare polyethylene terephthalate/thermoplastic polyurethane in situ fiber blends by"melting extrusion-quenching",which induces the fiber forming of thermoplastic polyurethane via volume elongation deformation.The results show that the effect of regulating volume elongation deformation can form thermoplastic polyurethane microfiber with uniform distribution and large diameter ratio.The fibers of thermoplastic polyurethane is increasing with enhancing the elongation flow field through improve rotational speed.The uniformly dense distribution and high diameter ratio of polyurethane microfiber significantly improved the tensile strength and impact strength of thermoplastic polyurethane blends.When the thermoplastic polyurethane content is 25%,increasing the rotational speed from 30rpm to60rpm,the tensile strength of blends increased from 35.7MPa to 44.5MPa,and the impact strength increased from 16.6kJ/m~2 to 88.5kJ/m~2.Moreover,highly fibrous thermoplastic polyurethane limited the molecular chain movement of polybutylene terephthalate and reduced the crystallization temperature and crystallinity of polybutylene terephthalate.The polyethylene terephthalate/montmorillonite composites with different montmorillonite content were prepared by using twin-screw extruder and eccentric rotor extrusion.The dispersion morphology of montmorillonite in polyethylene terephthalate/montmorillonite composites were observed by scanning electron microscope and transmission electron microscope,the crystalline behavior and crystal structure were investigated by the wide-angle X-ray diffraction and the differential scanning calorimeter.The thermal stability of the composites were characterized by the thermogravimetric analyzer,and the mechanical properties of the composites are tested by mechanical testing machine.The results show that the stripping intercalation of polyethylene terephthalate/montmorillonite composites prepared by eccentric rotor extrusion mechanism based on elongation flow field is better.Due to the volume elongation deformation,the molecular chains were less damaged.It has higher initial decomposition temperature and maximum weightlessness rate temperature.Moreover,when the montmorillonite content is 5%and 9%,it was found the formation ofβ-crystal type and better mechanical properties of composites.The polyethylene terephthalate/thermoplastic polyurethane blends with different thermoplastic polyurethane content were prepared by the means of twin-screw extruder and eccentric rotor extrusion.The two-phase morphology was observed by scanning electron microscope.the crystalline behavior and crystal structure were investigated by the wide-angle X-ray diffraction and the differential scanning calorimeter.The thermal stability of the blends are characterized by the thermogravimetric analyzer,and the mechanical properties of the blends are tested by mechanical testing machine.The results show that the two-phase compatibility of polyethylene terephthalate/polyurethane blends prepared by eccentric rotor extrusion based on elongation flow field is better,and it is found that the distribution and size of thermoplastic polyurethane phase are more homogeneous and smaller than that of thermoplastic polyurethane dispersed phase in the blends prepared by twin-screw extrusion.The thermal stability and mechanical properties are better than those prepared by twin-screw extrusion mechanism.In addition,when the thermoplastic polyurethane content is 25%,the impact strength of the blends reached 7.8kJ/m~2,compared to the pure polyethylene terephthalate,increased by 39.3%.The polyethylene terephthalate/polyurethane/montmorillonite composite system with different thermoplastic polyurethane content were prepared by using twin-screw extruder and eccentric rotor extrusion.The dispersion morphology and phase structure of polyethylene terephthalate/polyurethane/montmorillonite composite system were observed by scanning electron microscope and transmission electron microscope.The crystallization behavior and crystal structure were investigated by the wide-angle X-ray diffraction and differential scanning calorimeter,the thermal stability of composite system are characterized by thermal weight analyzer,and the mechanical properties of composite system are tested by mechanical testing machine.The results show that in the composite system prepared by eccentric rotor extrusion,montmorillonite dispersed in the matrix with smaller size and fewer layers,and the phenomenon of intercalation stripping is more obvious,the formation ofβ-crystal type of polybutylene terephthalate,and it also had a higher initial decomposition temperature and maximum decomposition rate temperature.Through the above experimental results of eccentric rotor extruder based on volume elongation deformation,the morphological evolution law in the process of blending via volume elongation deformation is found,and proved the elongation deformation is good for dispersion and distribution of polyester composite system.Moreover,the micro-fibers of thermoplastic polyurethane can be induced by the elongation flow field to prepare in-situ fiber composites with high strength and toughness.The composite system based on the elongation flow field dominated eccentric rotor extruder compared to the shear flow field-based twin-screw extruder is summarized.Under the volume elongation deformation,the montmorillonite are better stripped and dispersed,and have smaller thermoplastic polyurethane dispersed phase size.At the same time,the larger elongation deformation can make the polybutylene terephthalate form theβcrystal,and the composites have better mechanical properties.It highlights the significant advantages of volume elongation deformation for processing polyester composite systems,and provides an effective basis for advancing and developing elongation deformation processing technology.