Thermal pre-oxidation of polyacrylonitrile (PAN) fibers is a time-consuming and energy-consuming step in the production of PAN-based carbon fibers. In this paper, the effect of temperature on the structures and properties of PAN fibers cyclized in the supercritical carbon dioxide (Sc-CO2) medium was studied. The thermal behaviors of the PAN fibers were investigated by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The cyclization reaction was sensitive to the heating temperature and gas atmosphere. The FT-IR results of the PAN fibers treated in the Sc-CO2 confirmed that the degree of cyclization increased with the increase of the cyclization temperature. Compared with the PAN fibers treated in the air, the PAN fibers treated in the Sc-CO2 showed a higher degree of cyclization even at the same temperature. These findings might be related to the osmotic action of Sc-CO2 causing the fibers to be further arranged in a regular manner, which was favorable for the cyclization reaction. Moreover, as one kind of high diffusion and high heat transfer media, the heat release during the cyclization of PAN fibers could be quickly removed by Sc-CO2, which achieved the progress of the rapid-entry cyclization reaction.
The effect of supercritical carbon dioxide (ScCO 2 ) treatment with acetic anhydride (AA) for Kevlar fabric on the interfacial adhesion and mechanical properties of Kevlar fabric/epoxy composites was investigated. ScCO 2 treatment with AA remarkably affects the interfacial adhesion, thus improving mechanical properties. The effects of treating time on the surface modification and mechanical properties of composites were studied. Results demonstrated that the optimal condition is 100 C at 10 MPa for 60 min, as shown by the tensile strength and shear strength of the ScCO 2 -treated composites being 21.3 and 47.9% higher than those of the untreated ones, respectively. The mechanical properties demonstrated that ScCO 2 treatment provides an efficient and environmentally safe method for surface modification to improve interfacial interaction between the treated fiber and matrix with ScCO 2 treatment. POLYM. COMPOS., 40: E920-E927, 2019. POLYMER COMPOSITES-2019 FIG. 4. SEM images of the surfaces of Kevlar fiber (a) Kevlar untreated, (b) treating time of 30 min, (c) 60 min, and (d) 90 min. E924 POLYMER COMPOSITES-2019 DOI 10.1002/pc FIG. 7. SEM images of interlaminar shear ruptures of Kevlar fiber/epoxy Kevlar untreated, (b) treating time of 30 min, (c) 60 min, and (d) 90 min E926 POLYMER COMPOSITES-2019
In this paper, GO is mainly applied in the pre-oxidation experiment process of PAN fibers, and the exothermic heat in the PAN fiber pre-oxidation process is taken away by the GO with super-high thermal conductivity to accelerate the pre-oxidation progress.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.