Study On Biomimetic Modification Of Polyacrylonitrile Fiber And Its Reinforcement Mechanism For Composite Asphalt

Polyacrylonitrile fiber（PAN）is widely used in asphalt pavement to improve the performance of asphalt pavement due to its adsorption and reinforcement of asphalt.However,due to the weak effect of polyacrylonitrile fiber on the interface of asphalt,it is easy to cause interface debonding and fiber pulling phenomenon in actual use,which shortens the actual service life of asphalt pavement.Therefore,it is necessary to modify the fiber to improve the interface effect between the fiber and the asphalt.In this thesis,the surface modification of PAN was carried out by the polydopamine（PDA）bionic coating modification technology,and three modified fibers were prepared.1.PDA was used as the intermediate layer and grafted aminated reduced graphene oxide（NH₂-r GOs）on the surface of PAN to prepare NH₂-r GOs/PAN.2.PDA and silane coupling agent KH570 were co-deposited on the surface of PAN to prepare KD-PAN.3.PDA,silane coupling agent KH550（APTES）and polyethyleneimine（PEI）were co-deposition reaction to prepare P-P/A-P/PAN.The above-mentioned three kinds of modified fibers are mixed into asphalt to prepare fiber-modified asphalt.The rheological performance test and microanalysis of the three kinds of modified fibers are combined to explore the performance mechanism of modified fiber-enhanced asphalt.The research conclusions are as follows:（1）Characterization of the changes in the functional groups of the GOs before and after modification by Fourier infrared spectroscopy（FT-IR）.The crystallographic changes of NH₂-r GOs were characterized by X-ray diffraction（XRD）.The 3D and 2D topography of NH₂-r GOs/PAN were obtained by atomic force microscopy（AFM）and scanning electron microscopy（SEM）,and many lamellar materials appeared on the surface of modified PAN as NH₂-r GOs.The AFM force profile showed that the Young’s modulus of modified PAN was increased by 612%.By dynamic shear rheometry（DSR）,the G^*,G’and G’’of3%NH₂-r GOs/PAN modified asphalt were obtained,which increased about 8%,18%and 15%,respectively,over 3%PAN modified asphalt.（2）Surface elemental changes of KD-PAN were analyzed by scanning electron microscopy spectroscopy（EDS）.The microscopic morphological characterization of KD-PAN by SEM and AFM produced many granular substances on the surface and increased surface roughness.And the adhesion of fibers to SBS-modified bitumen was observed by SEM,and the infiltration of KD-PAN into SBS-modified bitumen was enhanced.The cone penetration test found that KD-PAN/SBS composite modified asphalt relative to the PAN/SBS composite modified asphalt shear strength was greatly improved,by DSR analysis of the rheological properties of KD-PAN/SBS modified asphalt,its G^*,G’and G’’respectively than PAN/SBS modified asphalt increased by 12.4%,20.5% and 11.2%.（3）Analysis of the reaction mechanism of PDA-APTES and PDA-PEI by UV-vis near-infrared spectroscopy（UV-vis）.Microscopic morphological characterization of P-P/A-P/PAN by SEM and AFM produced many granular materials on the surface,which basically covered the PAN surface and increased the surface roughness.The surface free energy analysis revealed that the surface free energy of P-P/A-P/PAN increased by 62%relative to PAN,and the adhesion work of P-P/A-P/PAN to asphalt increased by 26.5%relative to the adhesion work of PAN to asphalt,and the deformation resistance,elasticity and adhesion properties of P-P/N-P/PAN modified asphalt relative to PAN modified asphalt were obtained by DSR analysis,respectively The increases were 24%,37% and 19%.