Carbon Nanotubes And Polyester Composites And Fiber Preparation And Performance Research

Carbon nanotubes(CNTs)with perfect one-dimensional tubular structure,possess excellent electrical,mechanical and thermal properties,with wide potential applications in many different fields and industries,CNTs with broad development prospects,are considered to the mo st promising next-generation reinforcements for high-performance composite materials.Polyethylene terephthalate(PET)has good mechanical properties and is widely used in various fields.The addition of CNTs in the PET matrix can effectively improve its electrical,mechanical and thermal properties,and has been extensively studied.However,most studies are limited in the laboratory level and hard to scale up.Furthermore,it is much insufficient with CNTs reinforced PET fibers.By using industrial-grade MWCNTs as fillers and fiber-grade PET as the matrix,this thesis fabricates.MWCNT/PET composite slices by mechanical blending and melt extrusion granulation processes.Full-granulated composite fibers and masterbatch composite fibers were also prepared through the melt spinning process.The morphologies,thermal properties,crystallization properties,mechanical properties and electrical properties of composite slices and composite fibers were characterized through various test methods.Investigations on the MWCNT/PET composite slices indicate the good dispersibility of MWCNTs with the mass fraction of MWCNTs up to 3.0 wt.%and good interacted interfaces.The addition of MWCNTs significantly elevates the crystallization temperature and enhanced the crystallinity of PET.However,the thermal decomposition temperature decreases and the thermal stability of the composite slice declines.The electrical conductivities of the composites are significantly improved.When the mass fraction of MWCNTs is 3.0 wt.%,the apparant resistivity of composite splices decrease to 105?.When the mass fraction of MWCNTs is 5.0 wt.%,the apparant resistivity of the composite spline decreases to 103?.The addition of a small amount of MWCNTs also significantly increase the fracture strength of the composites.When the mass fraction of MWCNTs is 0.5 wt.%.the fracture strength increases by about 25.7%in comparision with pure PET slice.When the mass fraction of MWCNTs is 3.0 wt.%,the fracture strength increased by approximately 35.4%.Composite fibers are fabricated by fully granulation method and masterbatch method.Comparatively,the masterbatch method composite fiber has better spinnability.When the mass fraction is 1.5 wt.%,the MWCNTs are still well dispersed in PET matrix.Composite fibers by fully granulation method exhibit better interfacial interactions between MWCNTs and PET matrix.Adding a small amount of MWCNTs also significantly increase the crystallization temperature of fibers by masterbatch method.When the mass fraction of MWCNTs is 0.5 wt.%,the crystallization temperature elevates by 7?.Incorporating MWCNTs enhances the thermal stability of the composite fibers wit,and the increase grain size of PET,and the improved crystallinity.Post tensioning increase the order degree of PET crystals.The percolation threshold of primary fibers is between 1.5-2.0 wt.%.When the mass fraction of MWCNTs is 2.0 wt.%,the volume resistivity of composite fibers decrease to 107?·cm.