To improve the dispersion of graphene oxide (GO) nanosheets in sizing agent and to enhance the interfacial adhesion between GO and epoxy, GO nanosheets were chemically modified with cyanuric chloride (TCT) and diethylenetriamine (DETA). The functionalized GO (i.e. GO-TCT-DETA) with different contents was introduced into the carbon fiber (CF) interface by sizing process. The uniform distribution of GO sheets on CF surface and the enhancement of surface roughness were obtained. Moreover, significant enhancements (i.e., 104.2%, 100.2%, and 78.3%) of interfacial shear strength (IFSS), interlaminar shear strength (ILSS), and flexural properties were achieved in the composites with only 1.0 wt% GO-TCT-DETA sheets introduced in the fiber sizing. The GO-TCT-DETA in the interface region enhanced the stress being transferred effectively and the local stress concentrations being relieved. This study indicates that the utilization of functionalized GO is one of the alternative approaches for controlling the fiber-matrix interface and improving the mechanical properties of CF epoxy composites.

Reinforcing carbon fiber epoxy composites with triazine derivatives functionalized graphene oxide modified sizing agent

The effective control of crystallinity of covalent organic frameworks (COFs) and the optimization of their performances related to the crystallinity have been considered as big challenges. COFs bearing flexible building blocks (FBBs) generally own larger lattice sizes and broader monomer sources, which may endow them with unprecedented application values. Herein, we report the oriented synthesis of a series of two-dimensional (2D) COFs from FBBs with different content of intralayer hydrogen bonds. Studies of H-bonding effects on the crystallinity and adsorption properties indicate that partial structure of the COFs is “locked” by the H-bonding interaction, which consequently improves their microscopic order degree and crystallinity. Thus, the regulation of crystallinity can be effectively realized by controlling the content of hydrogen bonds in COFs. Impressively, the as-prepared COFs show excellent and reversible adsorption performance for volatile iodine with capacities up to 543 wt %, much higher than ...

Mechanistic Insight into Hydrogen-Bond-Controlled Crystallinity and Adsorption Property of Covalent Organic Frameworks from Flexible Building Blocks

Enhanced interfacial interactions of carbon fiber reinforced PEEK composites by regulating PEI and graphene oxide complex sizing at the interface

A novel strategy to simultaneously electrochemically prepare and functionalize graphene with a multifunctional flame retardant

Porous organic frameworks (POFs), a general term for covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state-of-the-art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in "turn-off" or "turn-on" fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/advs.201801116

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

Wave-transparent composites based on phthalonitrile resins with commendable thermal properties and dielectric performance

Enhanced thermal property via tunable bisphenol moieties in branched phthalonitrile thermoset

Many efforts have been devoted to tailoring the architecture of phthalonitrile (PN) polymers in recent years. Herein, we disclose a series of novel PN oligomers (PBP-Phs) bearing heteroaromatic phenyl-s-triazine moieties, serving as thermally stable segments in the polymer backbones. With bis(4-[4-aminophenoxy]phenyl)sulfone as a curing additive, PBP-Phs displayed commendable processability. After curing at high temperatures (up to 375 °C), the resulting networks (Th-PBPs) exhibited high glass transition temperatures ranging from 294 °C to 400 °C and outstanding thermal stability with a weight retention of 95% in N2 lying between 538 °C and 582 °C; the overall thermal properties were closely connected with the oligomer molar weights. Additionally, the feasibility of producing Th-PBPs reinforced with unidirectional continuous carbon fibers (CF) was evaluated. The results show that CF/Th-PBP laminates possess high flexural strength (1339–1855 MPa) and interlaminar shear strength (71.8–92.2 MPa).

Thermally stable phthalonitrile resins based on multiple oligo (aryl ether)s with phenyl-s-triazine moieties in backbones

Light-weight 1D heteroatoms-doped Fe3C@C nanofibers for microwave absorption with a thinner matching thickness

In this study, we describe a novel strategy to design and construct POSS-modified silane layer on carbon fiber (CF) to strengthen the interfacial adhesion and anti-hydrothermal aging behaviors of CF-reinforced copoly(phthalazinone ether sulfone)s (PPBES). POSS was first modified by 3-aminopropyltriethoxysilane (APS) to improve chemical reactivity. Without separation and purification, APS-c-POSS was used to functionalize CF to improve reactivity and ensure the covalent linkages between CF and POSS-modified silane layer. CF coated with POSS-modified silane layer was obtained by in situ hydrolysis of APS-c-POSS. FTIR and XPS confirmed the chemical bonds between CF and POSS-modified silane layer. Dynamic contact angle, dynamic wetting test and AFM tests demonstrated that POSS-modified silane coating can increase the wettability and roughness, which could improve interlaminar shear strength and flexural strength of CF/PPBES composites by 17.5 and 30.0% with slight enhancement on tensile strength of CF. The failure mechanisms of CF/PPBES composites with and without POSS-modified silane layer were both investigated by SEM in detail. Moreover, this layer was helpful to dynamic mechanical property and hydrothermal resistance of CF/PPBES composites. This study provides alternate strategy to modify CF with POSS, which will significantly broaden the application field of POSS in advanced composites.

One-pot strategy for covalent construction of POSS-modified silane layer on carbon fiber to enhance interfacial properties and anti-hydrothermal aging behaviors of PPBES composites

Lishuai Zong

Papers

Wave-transparent composites based on phthalonitrile resins with commendable thermal properties and dielectric performance

Enhanced thermal property via tunable bisphenol moieties in branched phthalonitrile thermoset

Thermally stable phthalonitrile resins based on multiple oligo (aryl ether)s with phenyl-s-triazine moieties in backbones

Light-weight 1D heteroatoms-doped Fe3C@C nanofibers for microwave absorption with a thinner matching thickness

One-pot strategy for covalent construction of POSS-modified silane layer on carbon fiber to enhance interfacial properties and anti-hydrothermal aging behaviors of PPBES composites