Improving dynamic mechanical property of bamboo pulp fiber reinforced epoxy resin composite treated by nano calcium carbonate

Abstract: In this study, in order to explore the enhancement mechanism of calcium carbonate (CaCO3) and develop the economizing, simplify and practical bamboo fiber reinforced composites, bamboo pulp fiber (BPF) and epoxy resin were served as the raw materials used to manufacture the fiber reinforced composites by means of vacuum-assisted resin transfer molding (VARTM). The BPF was modified with nano CaCO3 using impregnation. The dynamic thermo-mechanical property and interfacial property of the composites were analyzed using dynamic mechanical analysis. It was observed that when the test frequency was in the single digits (such as 1 Hz), the maximum storage modulus of the nano CaCO3 treated bamboo pulp fiber (IMBPF) reinforced epoxy resin composites (3 421MPa) increased by 30% in temperatures ranging from -20 to 120 ℃ compared to the control sample (2 627 MPa). When the test frequency was multiple digits (1, 2, 5, 10 and 20 Hz) it had a similar effect on the BPF/epoxy resin composites and IMBPF/epoxy resin composites, meanwhile, the storage modulus E', loss modulus E'' and loss factor tan δ all increased with the additional frequency and gradually moved to a higher temperature. The glass transition temperature of both BPF/epoxy resin composites and IMBPF/epoxy resin composites increased with the increase of the frequency, however, the loss factor tan δ had no significant change. In addition, the glass transition apparent activation energy Ea of IMBPF/epoxy resin composites (369.0 kJ/mol) with a lower glass transition temperature was lower than that of BPF/epoxy resin composite (495.8 kJ/mol), but the correlation between the logarithm of frequency (lnf) and the reciprocal of the glass transition temperature (1/Tg) for IMBPF/epoxy resin composites (R2=0.987 6) was higher than BPF/epoxy resin composites (R2=0.965 9), at the same time, the correlation coefficient (R2) of BPF/epoxy resin composites and IMBPF/epoxy resin composites was higher than 0.95. Moreover, when the composites were in glassy state and rubbery state at the selected temperature -20, 40 and 100 ℃, the dependence of the storage modulus E' of IMBPF/epoxy resin composites on the test frequency was higher than the BPF/epoxy resin composites, which suggested that the loading of CaCO3 particles (15%) affected the dependence of the storage modulus E' of the composites on test frequency to a certain degree. In the test temperature range of -20-120 ℃, the variation of the interface performance parameter A for IMBPF/epoxy resin composites was similar with that of BPF/epoxy resin composites, and the A value of IMBPF/epoxy resin composites was lower than the control sample. The A value of bamboo pulp fiber and matrix epoxy resin could reflect the temperature with the state of the composite interface. Therefore, the smaller the A value, the better the interfacial adhesion would be, thus the interfacial property of the composites were improved with nano CaCO3 impregnation.