Preparation And Properties Of Bamboo Fiber/Epoxy Resin Composites Modified By Oxidation And Carbon Nanotubes

In recent years,due to the global push for sustainable development,bamboo fiber reinforced epoxy resin composites(hereinafter referred to as bamboo fiber-based composites)have received more and more attention from researchers because of their low cost,easy availability and excellent mechanical strength properties.However,the problem of poor interfacial bonding between bamboo fiber and epoxy resin greatly limits the application of bamboo fiber-based composites,so it is urgent to study how to improve the interfacial bonding ability of fiber-resin two-phase in bamboo fiber-based composites.In this study,two different oxidation systems were selected to oxidize bamboo fibers,and the suitable oxidation system was selected to further improve the roughness of the fiber surface by amino-functionalized carbon nanotube grafting technique,and the effects of the two oxidation systems and carbon nanotube addition on the tensile strength and interfacial shear strength of bamboo fibers were comparatively studied.The bamboo fiber/epoxy composites were prepared by hot pressing and their tensile strength and interlaminar shear strength were tested and analyzed,and the strength values were evaluated by Weibull distribution,and finally the mechanism of action of oxidation technique and carbon nanotube grafting technique to strengthen the interface of bamboo fiber-based composites was investigated.The main findings of the study are as follows:(1)Two different modified bamboo fibers were produced by oxidizing bamboo fibers using TEMPO oxidation system and NHPI oxidation system,respectively.The bamboo fibers produced by different oxidation techniques showed large differences in microscopic morphology,tensile strength and interfacial shear strength.The single bamboo fibers prepared by the TEMPO system had greater structural and performance advantages,with surface roughness and interfacial shear strength of 92.1 nm and 10.13 MPa,which were improved by 31.4% and 64.46%,respectively,compared to the original bamboo fibers.In contrast,the surface roughness and interfacial shear strength of the specimens produced by the NHPI system were only 69.1 nm and8.36 MPa,which were only improved by 8.43% and 23.39%.Therefore,the TEMPO oxidation system is more suitable for the preparation of bamboo fiber-based composites with high interfacial bonding strength.The mechanism of the improved interfacial properties of modified bamboo fibers was investigated.(2)The effects of carbon nanotube addition on the morphology and properties of single bamboo fibers were investigated.Three different amino-functionalized carbon nanotube additions of 0.3wt%,0.5wt% and 0.7wt% were selected,and the grafting technique was successfully used to chemically graft amino-functionalized carbon nanotubes on the surface of bamboo fibers through the amide reaction between the amino group on carbon nanotubes and the carboxyl group on oxidized cellulose,and the threshold value of 0.5wt% of carbon nanotube additions was successfully found.The grafting technique significantly improved the fiber surface complexity and surface roughness,and resulted in surface roughness,tensile strength and interfacial shear strength of 175.0 nm,660.5 MPa and 15.90 MPa,respectively,for bamboo fibers at 0.5wt% carbon nanotube addition,which increased 212.5%,95.70% and 106.23%,respectively,compared with the original bamboo fibers.The mechanisms by which carbon nanotubes improve the tensile strength and interfacial strength of bamboo fibers,the causes of carbon nanotube agglomeration generation and the adverse effects caused by them were elucidated.(3)The modified bamboo fiber/epoxy resin composites were prepared by hot pressing technique.The grafting technique significantly improved the tensile strength and interlaminar shear strength of the bamboo fiber-based composites,and improved the interfacial bonding ability of the bamboo fiber-epoxy resin two-phase.When the addition of carbon nanotubes was0.5wt%,the mechanical strength of the composites had an optimal solution with tensile strength and interlayer shear strength of 78.03 MPa and 17.72 MPa,respectively,which increased by132.09% and 148.18% compared with the control group.The binding mechanism of the twophase interface of the bamboo fiber/epoxy composite was elucidated by combining the strength data analysis.