Rapid Preparation Of MWVNT/EP Composite By Photo Initiated Frontal Polymerization

Epoxy-based nanocomposites,combining the excellent performances of nanoparticles and epoxy resin(EP),and having a very important application prospect in many fields such as aerospace,automotive,power electronics,and building material decoration,attract people’ extensive attention.Among these nanomaterials,the outstanding performances of carbon nanotubes(CNTs)lead to the CNTs to be the mainstream of resin-based nanocomposite fillers.Currently,the main curing method of the EP nanocomposites is heating,which have a series of shortcomings such as long production cycle,high energy consumption,large pollution,easy aggregation of nanoparticles.This article is about using UV initiated horizontal frontal polymerization(UV-HFP)as a fast curing method to prepare CNTs/epoxy resin nanocomposites in order to compensate for the lack of heat curing.In addition,due to the extremely high surface energy of CNTs,they are easily agglomerated and difficult to disperse when using.Therefore,aiming at above situations,firstly,the CNTs were covalently modified by the ―on water‖ method.Secondly,the modified and unmodified CNTs were added into the EP,and the CNTs/EP nanocomposites were prepared by UV initiated horizontal frontal polymerization(HFP).Then the effects of the modified and unmodified CNTs on the HFP behaviors were studied.Finally,the properties of CNTs/EP nanocomposites were characterized.The main research contents and conclusions are as follows:(1)Using water as solvent,MWCNTs were covalently modified by diazotization of isoamyl-nitrite and 4-aminobenzoic acid,and benzoic acid groups were successfully grafted on the surface of MWCNTs.The results of TG and XPS tests show that the maximum grafting rate of benzoic acid groups on the surface of MWCNTs is about 12%.The modified MWCNTs still have good dispersibility in acetone after being placed for 3 months,which are still dispersed uniformly without sedimentation.The modified and unmodified CNTs were subjected to SEM testing,which shows that agglomerated phenomenon appeared in the SEM photo of unmodified MWCNTs,but not in the SEM photo of modified MWCNTs.(2)The CNTs/EP nanocomposites were prepared by UV-HFP.The effects of the modification and the grafting ratio of the CNTs on the HFP behaviors were studied.The results show that before the polymerization of HFP,only one or two drops of pre-prepared photoinitiator and EP mixture are added to the front of the glass boat,and the HFP can also be initiated by UV light;The amount of thermal initiator used is about 2wt% of EP,and the preheating time does not exceed 90s;When the modified CNTs was added,the frontal temperature increases,the frontal propagation rate increases,and the propagation angle decreases;With the increase of the content of CNTs,the maximum temperature of the frontal temperature increases,the propagation rate decreases,and the propagation angle increases;With the decrease of the grafting rate on the surface of CNTs,the maximum temperature of the HFP decreases,and the propagation angle increases;FTIR and DSC tests show that the products of the CNTs/EP composites by HFP have been completely cured.(3)The performance tests of CNTs/EP nanocomposites show that with the increasing of the content of CNTs,the thermal stability of CNTs/EP nanocomposites gradually increases;The thermal stability of EP composites with the modified CNTs were slightly improved;The higher the grafting ratio of CNTs,the better the thermal stability of its composites;With the increase of the content of CNTs,the glass transition temperature of the EP composites increases firstly and then decreases,the EP composite with the content of CNTs of 0.4wt% has the highest glass transition temperature;The thermal conductivity of the CNTs/epoxy resin is improved,and the thermal conductivity of the modified CNTs/EP composite material is also higher than that of the unmodified CNTs/EP composite material;With the increasing of the content of CNTs,the impact strength firstly shows a trend of increasing and then decreasing;The EP with 0.4wt% modified CNTs has the maximum impact strength,which is 655.05% higher than that of pure EP resin and 34.23% higher than that of EP composite with unmodified CNTs;The higher the grafting rate of carbon nanotubes,the higher the impact strength of the composites.The fracture section of EP resin,which is smooth and flat,is a typical brittle fracture.After adding CNTs,the EP resin composite material that has a rough section and a large number of scale on structures,shows a typical ductile fracture.With the sections of the EP composites with modified CNTs content of 0.4wt% and 0.6wt%,fibrous structure of the surface-wrapped EP resin was observed,while with other EP resin samples this phenomena were not observed;The higher grafting rate of CNTs on the surface,the rougher the fracture morphology of the composites section,indicating the better mechanical properties of the composites.