Study of Micro/nano Structure Control and Properties of Filled Poly(aryl Ether Nitrile) Composites

Author:Pan Hai

Supervisor:liu xiao bo

Database:Doctor

Degree Year:2019

Download:36

Pages:134

Size:14206K

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Polymer composites are of significance and widely welcomed for the applications in aerospace,marine-machinery,smart cars,electronic information,3D printing etc.for their enhanced properties arising from the easy processing,low cost,outstanding designability and high performance.Filled polymer composites have become one of the most economical methods for the development of new materials to meet increasingly demanding requirements of high-tech and cutting-edge technology.Current research suggests that the performance of filled composites mainly depend on the properties of fillers,polymer matrices and their interface.The characteristics of fillers(including functionality,surface,and structures etc.),as well as the interfacial properties between fillers and polymer matrices are primary factors determining the comprehensive performance of composite.For certain resin matrix materials,the interfacial properties between fillers and matrix will dominate the final properties of the filled composites.Therefore,the study of controlling properties of filled composites will come down to the designing and controlling of fillers and the interface.Poly(aryl ether nitrile)(PEN),a kind of special polymer with excellent comprehensive performance,has been widely used in aerospace,electronic information and automotive industry owning to its outstanding properties including heat resistance,chemical corrosion resistance,flame retardancy and high mechanical strength,etc.To further broaden its functional applications,Nd2Fe14B with outstanding magnetic properties and MWCNTs with outstanding electrical properties were selected as reinforcing fillers to enhance PEN.The dispersion and compatibility of fillers in PEN were studied through structural controlling including the sizes,surface roughness and micro/nano morphology of fillers.The dynamical rheological test was employed to theoretically calculate and analyze the compatibility of fillers,by which the influence of micro/nano structure on the properties of composites was discussed.Meanwhile,analysis of mechanical properties,electromagnetic properties and thermal properties of the composites were performance to reveal the influence of micro/nano structure of fillers on the interfacial compatibility of the composites.Based on the studies,the comprehensive performance of the filled composites can be adjusted and controlled.Specifically,the research is carried out as follows:(1)Nd2Fe14B particles with different sizes were prepared by ball milling.Nd2Fe14B particles with suitable size were selected by mechanical characterization as the research object.It was found that at a low loading(5 wt.%),Nd2Fe14B particles had good interfacial interaction with the matrix,which enhanced the tensile strength of the composite films.Results of rheological behavior showed that the addition of Nd2Fe14B hindered the movement of matrix molecular chain and significantly increased the storage modulus,loss modulus and complex viscosity of composite films.At the same time,the composite films exhibited excellent thermal stability and outstanding magnetic properties.(2)To further ameliorate the compatibility between Nd2Fe14B and the matrix,surface modification was studied.Fe3O4-FePc@Nd2Fe14B micro/nano particles with surface nanocrystallization,high roughness and self-compatibilizing properties were prepared by one-step solvothermal method.During the preparation processes,Fe3O4-FePc nanospheres self-assembly attached to Nd2Fe14B surface.The special micro/nano structure increased the specific surface area of the filler,endowing a larger contact area with the substrate.At the same time,phthalocyanine iron molecular chain on the surface of the microsphere was physically entangled with the matrix molecular chain to achieve interface self-compatibilization,making contribution to improving the performance of composite materials and realizing the effect of organic-inorganic micro-nano interface on the compatibilization of high-performance polymers.By the analysis of cross-section morphology,tensile strength and rheological behavior of the composite film,good interfacial compatibility between fillers and matrix was verified.When the filler content was 5 wt.%,the tensile strength of the composite film with an increment rate of 23.0% compared with that of pure films.When the filling content increased to 20 wt.%,tensile strength of the composite film was still higher than that of the pure film.Additionally,the introduction of Fe3O4-FePc nanospheres significantly reduced the coercivity of the composite film,making it exhibit soft magnetic material characteristics.(3)The filler system with multi-micro-nano structure was constructed with Nd2Fe14B and acidified MWCNTs by compounding.Various ratio of Nd2Fe14B and MWCNTs were selected to obtain various multi-micro-nano fillers.The effects of contents of fillers on the final properties of composites were also discussed.Also,the microwave absorption of the composite film was studied to expand its functional application.Performance of the composite film was obviously affected by changing the filling amount of fillers and adjusting the ratio of micron phase and nano phase in the fillers.Mechanical strengthening effect was better than that of Nd2Fe14B/PEN composite system.The storage modulus,loss modulus and complex viscosity were obviously improved,and the rheological behavior of composite film was mainly affected by the matrix resin under high frequency shear.Results showed that electromagnetic properties of the composites endowed the composite film excellent microwave absorbing properties.When the filling amount was 40 wt%and the mass ratio of MWCNTs to Nd2Fe14B was1:1,the reflection loss value of the composite film can reach-20 dB or less at all simulated thicknesses,and the absorption of electromagnetic waves of more than 99.0% can be achieved.(4)Replacing Nd2Fe14B with Fe3O4-FePc@Nd2Fe14B,a novel filler system with multi-micro-nano structure was designed to study the effect of filler on the performance of composite film.It was found that Fe3O4-FePc@Nd2Fe14B showed improved interfacial compatibility with the matrix than that of pure Nd2Fe14B filler.The compatibility was verified by the cross-sectional morphology,mechanical properties and rheological analysis.In addition,the introduction of Fe3O4-FePc nanospheres had an effect on the electromagnetic properties,which enabled the composite film good absorbing properties.When the filling amount was 40 wt% and the mass ratio of MWCNTs to Nd2Fe14B was3:1,the reflection loss of the composite film can reach-20 dB at all simulated thicknesses and the maximum reflection loss value was-47.0 dB.(5)Thermal decomposition kinetics of pure PEN film and composite films showed that the decomposition type of composite films was first-order reaction,and the average activation energy and pre-exponential factor was higher than that of pure PEN film.In the meantime,the multi-micro-nano filler system can significantly improve the aging life of the composite films and exhibited excellent thermal stability.Within the glass transition temperature,all composite films had a long aging life to meet the applications.