Preparation Of Brominated Carbon Nanotubes And Its Application As Toughener For Polyvinyl Chloride

The excellent conductivity,thermal conductivity and mechanical properties of carbon nanotubes make them of great potential in many applications.Carbon nanotube is mainly in the form of six membered ring,with a small amount of five membered ring and seven membered ring structure,the chemical stability is strong,but it is also limited in application.In order to broaden the application of carbon nanotubes,a series of carbon nanotubes modification technology is particularly important.In this paper,brominated carbon nanotubes with C-Br weak bond were prepared by bromination modification on the surface of carbon nanotubes and bromine.The prepared brominated carbon nanotube was applied to the toughening modification of PVC.The C-Br weak bond produced by the bromination of carbon nanotubes and the weak bond of C-Cl in PVC formed a micro crosslinking point after the high temperature fracture,and the toughness of PVC was improved.In the part of bromination modification,two methods of bromination modification,one-step method and two-step method,are put forward in this paper.The preparation of brominated carbon nanotubes by one-step method was to directly graft bromine onto the surface of carbon nanotubes.The two-step method of preparation of brominated carbon nanotubes was the first grafting of some carboxyl and hydroxyl groups on the carbon nanotube by the acidification oxidation process to form a new active point.Using the chemical reaction of the new active point and acroleyl chloride,the vinyl group was successfully grafted onto the carbon nanotube.Finally,the brominated carbon nanotubes were prepared by the chemical reaction of bromine and vinyl.By systematically studying the influencing factors of preparing brominated carbon nanotubes by one-step and two-step methods,the best conditions for the preparation of brominated carbon nanotubes by two methods are finally obtained.The morphologies,thermal stabilities,and chemical structures of the brominated carbon nanotubes prepared by the two methods were systematically characterized by transmission electron microscope,thermogravimetric analysis,Raman spectroscopy and X-ray photoelectron spectroscopy.The results show that the brominated carbon nanotubes prepared by the two methods have uniform appearance,good stability,grafting rate in 5wt%-10wt%,and chemical bonds between carbon nanotubes and grafted bromine.Two types of brominated carbon nanotubes are applied to the toughening modification of polyvinyl chloride by blending method.Firstly,a modified polyvinyl chloride masterbatch having a high density of cross-linking points was prepared,then the masterbatch was redispersed into the polyvinyl chloride resin by a two-roll mill.The prepared samples were characterizated by X-ray photoelectron spectroscopy,scanning electron microscopy,thermogravimetric analysis,differential scanning calorimetry,dynamic mechanical thermal analysis,simple beam impact testing machine,and universal material testing machine.The results show that the two modified sample fillers have good dispersion and stable performance and can play a toughening effect on polyvinyl chloride.When the amount of brominated carbon nanotubes was added to 5wt%,the impact strength of PVC splines can be increased by 75%,and the elongation at break of PVC strips increased by 43%when the amount of brominated carbon nanotubes was up to 4wt%.