Fabrication and Evaluation of Physical and Mechanical Properties of Magnetic-Cellulose Paper/Epoxy Resin Nanocomposites

Abstract
Background and Objectives: Despite the high potential applications of superparamagnetic cellulose fibers and papers, the hydrophilicity of cellulose and its resulting dimensional instability, as well as the significant loss of tensile strength due to the presence of magnetic nanoparticles on the fibers' surface, have limited the use of these functional materials. This study aimed to investigate the possibility of impregnating cellulose-superparamagnetic papers with epoxy resin and improving their physicomechanical behavior by converting them to nanocomposites.
Materials and Methods: In this research, superparamagnetic cellulose fibers were prepared by synthesizing of magnetite nanoparticles (Fe3O4) on the softwood cellulose fibers. First, suspension of cellulose fibers was prepared in distilled water at a temperature of 65 ° C, followed by the addition of iron chlorides II and III at a ratio of 2:1. Treated fibers were transferred out of solution and immediately added to 1 M sodium hydroxide solution at 60 ° C after dewatering to complete magnetic nanoparticle synthesis. After washing, the magnetic cellulose fibers were converted to magnetic cellulose paper (MCPap) with a grammage of 60 g/m2. For comparison, non-magnetic paper (CPap) with the same grammage was produced. The papers were impregnated with a two-component epoxy resin and cellulose paper / epoxy resin (EP-CPap) composites and magnetic-cellulose paper/epoxy resin (EP-MCPap) nanocomposites were made. Microscopic observation, X-ray diffraction, magnetometry, ash determination, static tensile testing, water absorption, and thickness swelling were performed on the specimens and the results were assessed.
Results: The successful in situ synthesis of spherical magnetic nanoparticles on the surface of cellulose fibers was confirmed by FESEM micrographs. The results of the XRD and VSM tests showed a successful synthesis of magnetite nanocrystals with a diameter of about 7 nm and a superparamagnetic behavior. The weight ratio of magnetic nanoparticles in MCPap paper was approximately 14.5 percent. The results of the static tensile test confirmed the significant improvement in the tensile behavior of EP-CPap and EP-MCPap over the initial papers. Also, the maximum tensile strength of EP-MCPap did not show a significant difference with EP-CPap, while the tensile strain and energy at the break of EP-MCPap were significantly higher and the modulus of elasticity was significantly lower than EP-CPap. In EP-CPap samples, the maximum water absorption and thickness swelling and the speed to reach the peak assessed values were higher than those in EP-MCPap specimens.
Conclusion: Microscopic analysis of the paper structure of CPap and MCPap indicated enhanced fiber-fiber interface quality in CPap paper; this observation was attributed to the influence of the presence of magnetic nanoparticles on MCPap paper fibers and the disturbance in the development of the interface between adjacent cellulosic fibers. Despite the considerable advantage of the tensile strength of CPap paper over MCPap paper, probably due to the limited availability of epoxy resin on all fiber surfaces in CPap paper, the tensile strength of EP-MCPap and EP-CPap nanocomposite was not significantly different. It appears that despite the negative effect of the presence of magnetic nanoparticles on the mechanical properties of MCPap paper due to the less dense texture of the paper, the epoxy resin's permeability is improved and therefore the epoxy nanocomposites' tensile behavior and water absorption and thickness swelling are improved. The results of this study confirmed that the impregnation of the magnetic papers with epoxy resin significantly improves the physicomechanical behavior and consequently the development of their potential applications.