An effective non‐covalent grafting approach to functionalize carbon fiber with polyethyleneimine in supercritical fluid to enhance the interfacial strength of carbon fiber/epoxy composites

Abstract

A facile and effective approach to functionalize carbon fiber (CF) by non‐covalent grafting branched polyethyleneimine (PEI) in conventional and supercritical methods was proposed. Fourier transform infrared (FTIR) spectrometry, X‐ray photoelectron spectroscopy, Raman, scanning electron microscopy (SEM), atomic force microscopy (AFM), dynamic contact angle analysis (DCA), and single fiber tensile testing were carried out to characterize the CF reinforcements. Interfacial shear strength (IFSS) and transmission electron microscopy were performed to investigate the composites interfacial properties. Experimental results indicated that the non‐covalent grafting polyethyleneimine on CF–COOH increased the polarity, wettability, and roughness of carbon fiber surface. The interfacial shear strength improved significantly using the two methods, especially in supercritical methanol, which further confirmed the previous study. Single fiber tensile strength did not deteriorate owing to the green modification. Moreover, this convenient project was believed to have widely potential applications in high performance composites. POLYM. COMPOS., 39:E2381–E2389, 2018. © 2017 Society of Plastics Engineers

Integrated sensing layer of bacterial cellulose and polyethyleneimine to achieve high sensitivity of ST-cut quartz surface acoustic wave formaldehyde gas sensor

“…Polyethylenimine (PEI) is a typical water-soluble polyamine, with a polar group (amino group) and a hydrophobic (vinyl) structure that allow it to be bound to different substances [28,29]. It has a wide range of applications in polymer dyes [30], papermaking [31], fiber modification [32] and biomedicine [33]. The PEI molecules contain a large number of amino groups, which have a good selectivity to adsorb the formaldehyde molecules and are suitable for detection of formaldehyde gas [34][35][36].…”

Grafting hyperbranched polymer with terminal hydroxyl groups onto carbon fiber surface in two‐step polycondensation for improving the interfacial properties of carbon fiber/epoxy resin composite

“…The amorphous structure on the CF surface could correspondingly increase the active atoms, providing more react sites for subsequent grafting, which was favorable for improving the interfacial adhesion of the CF composite. In addition, the integrated area ratio of the A band to the G band (IA/IG) was widely considered to be an assessment of amorphous carbon structures and some oxygen-and/or nitrogen-containing functional groups and the relative degree of surface functionalization on CF [25,26]. Figure 6 showed that the microstructure heterogeneity changes of the modified CFs surface.…”

“…There was no suitable interphase for untreated CF/epoxy composite, the crack tip extended perpendicular to the fiber surface directly, which would lead to fiber fracture under low stress. For CF-HBPH/composite, the HBPH interphase could act as a shielding layer which would ease the stress concentration [27]. When the major crack passed to them, HBPH could derive more and more micro-scale cracks, which made the communication process become difficult and intricate, meanwhile, it could prevent the crack tip from directly attacking the fiber reinforcement and efficiently absorb more fracture energy, thereby increasing the composite flexural properties.…”

Enhancing the Interfacial Properties of Composites by Grafting Polyethylene Glycol and Polyvinyl Alcohol Onto a CF Surface

“…The earliest CFs can be traced back to Edison's application of carbonized cotton yarn. CFs have good in‐plane tensile properties compared with traditional metallic materials , and therefore CF ‐reinforced polymer composites have found a wide range of applications in the aerospace industry and opened up many possibilities for new long‐life products for producers and consumers. However, because CFs produced by the dry‐spray wet‐spinning processes have a low content of active oxygen (O) functional groups and possess low‐roughness surfaces, they do not easily combine with matrices.…”