Study On Surface Modification Of UHMWPE Fiber And Its Reinforced Composite Interface

The increasing demand for lightweight and high-performance materials has expanded the prospects and value of composite materials,especially fiber-reinforced composites.Among all reinforcing fibers,ultra-high molecular weight polyethylene(UHMWPE)fibers have attracted much attention from researchers and industrial engineers for their excellent mechanical properties,high chemical resistance and impact strength.The lack of polar functional groups and low surface free energy result in poor adhesion of the fiber to the matrix.The degree of fiber-polymer infiltration,especially at the fiber-matrix interface,determines the performance of UHMWPE fiber-reinforced composites.Adhesion can be promoted by both physicochemical or mechanical locking,and the combination of these two different primary pathways can construct new reinforcing interfaces for the composite.The bionic surface modification method of oxidative autopolymerization of dopamine to create thin layers of polydopamine(PDA)can build bridges between the polymer matrix and the fibers,while the low-temperature solutionbased growth technique can form rigid whiskers on the coating surface to enhance load transfer and interfacial adhesion.Based on the requirement of functionalized coating that does not damage the fiber body and its process is green and controllable,this project uses PDA functionalized coating as a carrier,prepares PDA coating by mild and simple solution impregnation,and modifies UHMWPE fibers by in situ uniform growth of ZnO nanoarrays on PDA surface by lowtemperature hydrothermal method to study the influence of inherent properties of PDA and microstructure parameters of nanoparticles on the interfacial properties of composite materials.The effect of PDA intrinsic properties and nanoparticle microstructure parameters on the interfacial properties of the composites was investigated;the surface properties of multi-scale reinforced UHMWPE fibers were studied systematically from the microscopic interfacial properties to the macroscopic mechanical properties of the composites,and the interfacial reinforcement mechanism was revealed to provide theoretical and scientific basis for optimizing the design of reasonable interfacial phase microstructures of UHMWPE fiberreinforced composites.The specific research contents and main findings are as follows.(1)PDA-functionalized UHMWPE fibers and interfacial properties study.Inspired by the components of adhesion proteins in mussels,dopamine self-polymerization was used to form a PDA film on the surface of UHMWPE fibers.Controllable PDA morphology was achieved by regulating the kinetic factors of dopamine polymerization(e.g.reaction solvent,reaction time,etc.).When the ethanol content in the solvent is 20%,the tensile strength of the fiber can be increased by a maximum of 11.1%.When the dopamine concentration is 2 g/L,the interfacial shear strength increases with the increase of reaction time,and the maximum can be enhanced by 146.7%,but when the reaction time exceeds 24 h,the interfacial strength slightly decreases;when the reaction time is 84 h,the interfacial bond strength is enhanced by 57.7% when the ethanol content is 40%,influenced by the solvent effect.The main reason for the interfacial enhancement is that the PDA coating can introduce highly polar catechol and amino groups on the surface of UHMWPE fibers,thus enhancing the compatibility with the resin matrix.(2)Preparation of UHMWPE-PDA-ZnO fibers and study of their interfacial properties.By secondary functionalization modification of PDA,ZnO nanorod arrays were grown in situ on the fiber surface using hydrothermal method to achieve controllable ZnO nanorod aspect ratio in polyethyleneimine(PEI)-mediated reaction system.Among them,the seed layer is the main reason for the orientation of ZnO nanoarrays along the c-axis.ZnO nanorods with aspect ratios ranging from 10 to 32 were prepared at PEI concentrations from 0 to 5 m M,respectively,and the interfacial bond strength could be enhanced by a maximum of 63.6%.The mechanical interlocking between the ZnO nanorods on the fiber surface and the resin matrix was the main reason for the enhancement of the interfacial strength.(3)Preparation of UHMWPE laminates and their mechanical properties.UHMWPE/WPU,UHMWPE-PDA/WPU and UHMWPE-PDA-ZnO/WPU laminates were prepared by hot pressing process,and the influence law of UHMWPE fabric modification on the interfacial properties of the composites was studied by 180° peeling,short beam shearing and dynamic mechanical properties.Among them,the peel strength and interlaminar shear strength of UHMWPE-PDA-ZnO/WPU composites were improved by 4 times and 70.14%,respectively,compared with UHMWPE/WPU,while their tanδ values indicated that the system could absorb more energy.In summary,the structural design and controllable preparation of high-performance organic-inorganic nano-reinforced materials can obtain controllable composite interfaces with minimal damage to the original mechanical properties of UHMWPE fibers,which provides a new research idea for the interfacial modification of UHMWPE fiber/resin-based composites,but the corresponding understanding of the strengthening mechanism at the molecular/atomic level requires advanced characterization methods and techniques.The corresponding understanding of the reinforcement mechanism at the molecular/atomic level requires more advanced characterization methods and techniques.