Preparation And Study On Performance Of Epoxy Matrix Composites Modified With Shellfish Powder

As natural inorganic-organic hybrid materials, shellfish is a kind of natural biological nano-composites which is cheap and easy to get, with higher strength and toughness. In this paper the high-performance shellfish powders, treated with coupler and calcined in various temperatures, were used to be the filler of thermosetting resin-epoxy, which was made of rigid particles and modified to epoxy resin matrix composites. And then the basic mechanical properties, friction properties and microstructure of composites were measured.The active group changes, crystalline structure transformations and carbon quantitative analysis of the composites were investigated by Fourier transform infrared spectrometer, X-ray diffraction and elemental analysis, respectively. The results proved the existence of organic components, which mainly were the amino acid and ammonium. The main part of the inorganic calcium carbonate transformated from aragonite to calcite crystal which is more conducive to cleavage. Organic ingredients burned completely at 700℃, which is the temperature of the major turning point. Then various proportions modified epoxy matrix composites were prepared, filled with the natural and calcined shellfish powders treated at different temperatures, ultrasound and the coupling agent.The curing kinetics of composites was investigated. The composite system can lower the curing reaction temperature, made the reaction more stable. The research of the basic mechanical properties of composites showed that the toughness of each system was improved differently. System BA modified with coupler added natural powder has better toughening effect than system BB without coupler. But both systems achieved the best toughening effects when the powder reached the weight percent of 3%. The impact toughness of system SB modified without coupler powder was superior to system SA modified with coupler added powder. They all reached their maximal impact toughness at 700℃. The maximal impact toughness of system SB increased by 57.8% than pure epoxy. All systems maintained a relatively high strength while the toughness was improved. SEM confirmed that particles in the matrix were dispersed quietly uniformly. The pattern of impact fracture surfaces showed rougher and displayed the characters of ductile fracture. The addition of shell powders raised the humidity resistance of the composites obviously.Friction properties of all systems were improved. The antifriction effect of system BA was most obvious. The lowest friction coefficient decreased 33% than pure epoxy. BA, BB two systems both had better wear resistence, the lowest wear rate decreased by 19% and 16% than pure epoxy respectively. System SA has less wear resistence. At 700℃system SB reached a minimum wear ratio which decreased by 16% than pure epoxy. The wear mechanisms of the materials were presumed according to morphology characteristics of the wear surfaces by SEM.Micro-hardness of composites kept a good coincidence with the friction performance. The great micro-hardness of the materials lowered the friction coefficient, and the wear ratio is; and vice versa.The positron annihilation lifetimeÏ„3, annihilation strength I₃ and relative free volume fraction f_app were measured by positron annihilation technique. The modified mechanisms of composites were discussed. The results showed: Positron annihilation lifetimesÏ„₃ of all systems were no major changes. The annihilation intensity I₃ all showed a downward trend, but the drop ratio of SA is greater than SB. The presence of coupler caused the difference from SA to SB. The relative free volume fraction f_app of various systems kept the same trends with the annihilation intensity I3. Positron annihilation technique detected the role of the interface, between the powders and matrix, and the microstructure of composites.With a result, system BA modified with a normal shell and coupling agent had the best integrated properties. System SB at 700℃exhibited excellent performance. The reasons of various properties change of composites were discussed from the perspectives of the particle dispersion, coupling of the interface, particles own properties and the microstructure of composites.