Non-Covalent Bond Surface Modification Of Carbon Nanotubes And Preparation Of Carbon Nanotube/Natural Latex Composite Materials

Carbon nanotubes(MWCNTs)have ultra-high strength,great toughness,and excellent electrical and thermal conductivity due to their unique structure.However,due to the large aspect ratio of carbon nanotubes and the high surface energy,the carbon nanotubes are easy to agglomerate and difficult to disperse in the matrix.So it is important to modify them.In this paper,MWCNTs were modified non-covalently by dopamine and sodium methylene perylene naphthalene sulfonate under the action of mechanical grinding.MWCNTs modified with dopamine and sodium methylene perylene naphthalene sulfonate were prepared.Natural latex(NRL)was used as a matrix,and the modified MWCNTs were used as fillers.The properties of the modified MWCNTs and unmodified carbon nanotube/natural rubber composites were compared.TEM,TGA,Raman methods were used to study the dispersion effect of carbon nanotubes in water and the interaction between carbon nanotubes,dopamine and sodium methylene perylene naphthalene sulfonate.The mechanical properties,Payne effect,and electrical properties of the modified carbon nanotubes/natural rubber composites were systematically studied by the testing methods such as mechanical properties,RPA,and surface resistance.(1)The results showed that under the action of colloidal milling of MWCNTs,and after ultrasonic treatment,dopamine and carbon nanotubes formed ?-? conjugation.So dopamine could adhere to the surface of multi-walled carbon nanotubes.Thus,non-covalent modification of multi-walled carbon nanotubes by dopamine were obtained.TGA showed a certain interaction between dopamine and carbon nanotubes.Transmission electron microscopy showed that carbon nanotubes were uniformly dispersed in water and could stably exist in water.Dopamine significantly improved the dispersibility of carbon nanotubes.Raman spectroscopy showed that the defects of carbon nanotube were significantly reduced after modification.(2)By comparing the experimental results,it was found that carbon nanotubes more easily formed a uniform filler network structure in the latex matrix after dopamine modification.The mechanical properties showed that the properties of dopamine-modified carbon nanotubes/natural latex composites had been improved.The vulcanization performance showed that the vulcanization speed of CNT / NRL composites modified by dopamine was decreased,and the dispersion effect of carbon nanotubes in the matrix became better.The RPA results showed that the modified carbon nanotube/natural latex composites had improved storage modulus and reduced loss factor.Electrical properties showed that the dispersed network of dopamine-modified carbon nanotubes in the latex matrix was more stable.The conductive paths formed were more smooth,and the surface resistance was smaller.(3)The studies had shown that sodium methylene perylene naphthalene sulfonate modified carbon nanotubes made the dispersion of carbon nanotubes in water more stable through ?-? interaction.TEM showed that the dispersion of carbon nanotubes in water was significantly improved.Raman spectroscopy showed that sodium methylene perylene naphthalene sulfonate could improve the crystalline state of carbon nanotubes,reduce the disordered structure and increase the ordered structure.At the same time,in the presence of sodium methylene perylene naphthalene sulfonate,a uniform filler network could be formed.The storage modulus of the CNT/ NRL composite was increased,and the loss factor was decreased.Electrical properties showed that carbon nanotubes could form more uniform conductive paths in the matrix after modification with sodium methylene perylene naphthalene sulfonate.(4)Dopamine and sodium methylene perylene naphthalene sulfonate were used to synergistic modification for carbon nanotubes.Zeta potential test showed that the effect of synergistic modification was better than single modification.With the increase of the content of carbon nanotubes,the mechanical properties of the composites improved significantly.The vulcanization speed of natural latex composites increased with the increase of carbon nanotubes.It was because that the thermal conductivity was increased and the vulcanization speed was increased with the increasing of carbon nanotubes.RPA showed that the storage modulus of carbon nanotube/natural latex composites had increased and the loss modulus had decreased.When 3phr NNO-PDA-MWCNT filler was added,the volume resistance of the composite reached to 10~5?.