| Halloysite nanotubes(HNTs),as a kind of aluminosilicate minerals and novel natural inorganic nano materials with its special hollow tubular structure and surface structure,has the advantages of low price,abundant source,strong thermal stability and so on,,and thereby got extensive utilization in the fields of composite materials,ceramics,nano templates and so on,which has become a hot spot in the research of new materials.As a filler,HNTs can effectively enhance the properties of polymer materials.In addition,due to the polar surface characteristics of HNTs,it has good dispersibility in the polar polymers such as epoxy resin(EP).At present,most research concentrated on HNTs/oily epoxy resin composite,while the research on HNTs/waterborne epoxy resin is rarely reported.The purpose of this paper is to select the waterborne epoxy resin as the matrix,and the HNTs is used as the reinforcing material to prepare the waterborne epoxy resin composites with excellent performance and environmental protection,which is expected to be applied to the surface of mechanical equipment or industrial coating.The main work is as follows:Firstly,the HNTs/waterborne epoxy resin composite material was prepared through ultrasonic dispersion and mechanical blending using the marketed waterborne epoxy resin as matrix.The dispersion process was explored.Then take bisphenol A expoxy E-44 as raw material,the nonionic waterborne epoxy resin and the HNTs/waterborne epoxy composite resin were prepared.The effect of HNTs on the performance of waterborne epoxy resin and film were studied.HNTs were modified by silane coupling agent,and a series of m-HNTs were gotten.The thermal stability and rheological behavior of series m-HNTs and series m-HNTs/waterborne epoxy resin composites were tested.The optimum modified process was determined.Secondly,Take bisphenol A expoxy E-51 as raw material,the nonionic waterborne epoxy resin and its HNTs/waterborne epoxy resin composites and m-HNTs/ waterborne epoxy resin composites were prepared under optimum conditions.The effects of HNTs and m-HNTs content on the fracture morphology,thermal stability,emulsion particle size,rheological behavior and film properties were analyzed.Finally,the m-HNTs/waterborne epoxy resin coating was prepared with the addition of m-HNTs/waterborne epoxy resin emulsion,as well as fillers,dispersing agent,defoaming agent,wetting agent,leveling agent and thickening agent and other additives.Effects of various additives on the coating properties were systematically discussed.Effects of coating,rolling and brushing methods on coating properties were studied.Based on the above work,the conclusions were as follows:(1)The ultrasonic dispersion and mechanical blending process were favorable to prepare homogeneous HNTs/waterborne epoxy resin composites.The research showed that the best ultrasonic process conditions were as follows:ultrasonic power was 80%,ultrasonic time was 30 min,ultrasonic mode was ultrasonic time/stirring time =10 min/5 min,and this test cycle was repeated for two times.Composites resin prepared under this condition had lower particle size distribution index PDI.Light scattering and rheological analysis showed that the emulsion was endowed with bettercolloid stability.Scanning electron microscopy(SEM)image showed that HNTs were able to uniformly disperse in composites.The fracture characteristic of film transferred from brittle fracture to ductile fracture.The storage modulus increased and the loss factor decreased,However,the thixotropy of the composite system was reduced,the thermal stability of the composite and the comprehensive performance of the film were better when w(HNTs)=2%.However,when the HNTs content was greater than 5%,the comprehensive properties of composite films decreased.(2)Fourier transform infrared(FTIR)and X-ray photoelectron spectroscopy(XPS)test results showed that silane coupling agent KH550 has been successfully coupled to HNTs.And C atoms in m-HNTs had three kinds of binding states and the binding states of the two Si atoms.SEM、transmission electron microscopy(TEM)and XRD results showed that the crystal structureand microstructure of HNTs did not change.The thermal decomposition temperature of m-HNTs was improved effectively compared to HNTs.When the mass ratio between KH550 and HNTs was 1:2,the thermal decomposition temperature reached the highest,indicating improved thermal stability,and the rheological behavior of the composite emulsion system was improved.(3)With proper addition of HNTs and m-HNTs,the average particle size of the composite emulsion increased,the PDI decreased,rheological behavior was improved.The fracture characteristic of composites film transferred from brittle fracture to ductile fracture,The thermal decomposition temperature of waterborne epoxy resin latex film increased,suggesting improved thermal stability.The water resistance of the compositesalso got improved.In addition,the stiffness of film wasenhanced with the addition of HNTs and m-HNTs.Compared with HNTs,average particle size and PDI were further reduced,the thermal stability,water resistance and comprehensive performance of the film were further improved with the addition of m-HNTs.When w(m-HNTs)=3%,the average particle size and PDI rached the minimum,the decomposition temperature increased by 22 ℃,the lowest water absorption reduced to10.01%.When w(HNTs)increased from 0% to 3% at the shear rate of 1 s-1,the viscosity increased from 0.65 Pa.s to 2.36 Pa.s,the storage modulus increased by four times.However,when HNTs were repalced by m-HNTs,the viscosity increased from 0.65 Pa.s to 7.26 Pa.s,the storage modulus increased by an order of magnitude,and the delta of system further reduced.When w(m-HNTs)>5%,obvious aggregation took place in m-HNTs,and the comprehensive properties of the composites were weakened.(4)The formulation of coating additives were determined,the results were as follows: w(dispersant)=3%,w(thickener)=0.6%,w(defoamer)=0.2%,w(wetting agent)=0.15%,w(leveling agent)=0.2% and w(pigment filler)=20%.(5)The film produced by roll coating was even and smooth.With respect to spray technology,the viscosity of the emulsion can’t be too large,and the as-prepapred film was more smooth.As to brush techonology,the requirement of the emulsion viscosity was strict.The viscosity of coatings were higher than the emulsion matrix,as well as the storage modulus and loss modulus.The addition of additives,such as thickners,leveling agent,was beneficial to theformation of crosslinking structure and enhancement in the molecular interaction. |
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