Search

The design and preparation of hydrophobic, wear-resistant, and thermally conductive multifunctional composites is an important direction of scientific research and application. In this study, A-CF/EP/FEP composites were prepared by incorporating APDMS-modified carbon felt (A-CF) into an epoxy resin (EP) and fluorinated ethylene propylene resin (FEP) mixed resin. The low surface energy of FEP, good adhesion of EP, and the supporting of carbon felt framework endow the A-CF/EP/FEP composites with hydrophobicity, wear resistance, and thermal conductivity at the same time. Firstly, the water contact angle (WCA) of A-CF/EP/FEP composites with 20 wt% FEP reaches 109.9 ± 2.6°, and the WCAs of all composites with different FEP contents (10, 20, 30, 40, and 50 wt%) is greater than 90°, indicating the composites have a hydrophobic surface. Secondly, the A-CF/EP/FEP composites have high wear resistance and maintain long-term hydrophobicity after tribological tests, because the residual debris and nanoparticles generated by external loading adhere to the friction interface, regenerating the microstructure of the hydrophobic surface. Finally, the A-CF/EP/FEP composites have high thermal conductivity up to 0.38 W/(m·K), which is 1.81 and 2.0 times that of pure EP and EP/FEP composites, respectively. This is because a relatively complete heat conduction network is formed after the addition of A-CF to the composites. The synergy among epoxy resin, FEP, and the A-CF filler plays a particularly important role in constructing hydrophobic surfaces and improving wear resistance and thermal conductivity. The EP enhances adhesion, the FEP supplies low surface energy, and the A-CF framework improves the wear resistance of A-CF/EP/FEP composites. This work provides ideas for the design and preparation of multifunctional composites and will underlie the application of high-performance epoxy resin and its composites. [ABSTRACT FROM AUTHOR]

Generally, high‐performance epoxy resins, which are derived from aromatic compounds have two major disadvantages of yellowing and brittleness, and thus it presently remains a challenge for the facile synthesis of epoxy resin with excellent ultraviolet resistance and superior strength and toughness. Herein, a novel bio‐based epoxy resin diglycidyl ester of camphoric acid (DGECA) was synthesized from the renewable camphoric acid via an efficient and scalable route. The chemical structure of DGECA was carefully characterized by Fourier transform infrared (FT‐IR), nuclear magnetic resonance (NMR), and mass spectrometry before being cured with methylhexahydrophthalic anhydride (MHHPA). Compared with the cured diglycidyl ether of bisphenol A (DGEBA)/MHHPA, the cured DGECA/MHHPA system achieved 11.5%, 16.7%, and 109.4% increment in flexural strength (126 MPa vs. 113 MPa), modulus (2.8 GPa vs. 2.4 GPa), and impact strength (6.7 kJ/m2 vs. 3.2 kJ/m2), respectively. Moreover, cured DGECA exhibited extremely lower ultraviolet absorption (0.038A) and better ultraviolet resistance than that of cured DGEBA. This work provides a new strategy to synthesize epoxy resin with excellent ultraviolet resistance and high toughness by using the unique structure of renewable feedstock. [ABSTRACT FROM AUTHOR]

[Display omitted] • The chemical and topological structures of flame retardant were regulated at the same time. • Modified epoxy resin showed UL-94 V0 rating and LOI above 32.6 vol% with phosphorus content of only 0.24%. • Impact strength was increased by 113% at 25°C and by 96% at −196°C after modification. • Tg was increased from 172°C for pristine resin to 194°C for modified system determined by DMA. • Flexural strength and modulus of modified epoxy were increased by 26% and 19%. Endowing epoxy resins with simultaneously improved flame retardancy, toughness and strength as well as glass transition temperature (T g) is a big challenge for us. Herein, a hyperbranched flame retardant (HBFR) with rigid backbone structure was synthesized through a facile strategy. Upon the incorporation of HBFR, the modified diglycidyl ether of bisphenol A (DGEBA) with phosphorus content of only 0.24 wt% exhibited better flame retardancy beyond expectation, showing UL-94 V-0 rating and limited oxygen index (LOI) above 32.6 vol%. Meanwhile, the modified epoxy resin demonstrated superior toughness, indicated by the more than 96% increment in impact strength both at 25 and −196°C, due to the enlarged free volume originated from hyperbranched structures. Furthermore, the T g , flexural strength and modulus of modified epoxy systems were also significantly increased because of the rigid backbone structure and high crosslinking density afforded by HBFR. This work provided us an attractive strategy for simultaneously improving the flame retardancy, toughness, T g and strength of commercial epoxy resins. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel hyperbranched flame retardant was synthesized from renewable resources. • The hyperbranched flame retardant endowed epoxy resin with UL-94 V-0 rating. • The impact strength at −196 °C of modified epoxy resin was increased by114%. • The flexural strength, modulus and T g of modified epoxy resin were simultaneously improved. It is highly desired yet very challenging to overcome the flammability and brittleness of epoxy resin without compromising its glass transition temperature (T g). Herein, an epoxy-terminated hyperbranched flame retardant (EHBFR) was designed and synthesized from 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and renewable protocatechualdehyde as well as guaiacol. When the synthesized EHBFR was taken to modify diglycidyl ether of bisphenol A (DGEBA), it is found that the incorporation of EHBFR remarkably improved its fire safety, endowing it with a UL-94 V-0 rating and a limiting oxygen index (LOI) of 33.0 vol%. Meanwhile, the notched impact strength of modified DGEBA at 25 and −196 °C (quenched by liquid nitrogen) exhibited significant increment by 135% (from 3.39 to 7.97 KJ/m2) and 114% (from 2.34 to 5.01 KJ/m2), respectively. Moreover, the T g of modified epoxy resin did not show any decrease, and even increased from 172 to 194 °C when the content of EHBFR was 10 wt%, due to the synergistic effect of rigid DOPO-containing groups and high crosslink density. This work offers an efficient strategy for constructing high-performance epoxy thermosets with excellent flame retardancy, superior toughness and strength, as well as elevated T g. [ABSTRACT FROM AUTHOR]

With the purpose to obtain an eco-friendly flame retardant for epoxy resin, a facile method for the synthesis of a bio-based epoxy monomer containing DOPO units (DGEBDB) from lignin-derived vanillin and guaiacol, was presented in this work. During the synthesis process, guaiacol acted as both reactant and solvent. And it could be recycled in situ and re-used as the fresh one. In order to evaluate the flame retardancy of DGEBDB, it was mixed with diglycidyl ether of bisphenol A (DGEBA) and cured with 4,4-diaminodiphenylmethane (DDM). Results showed that, DGEBDB demonstrated a good compatibility with DGEBA, and the mechanical properties of cured resins were obviously improved with the addition of DGEBDB. As expected, the limiting oxygen index (LOI) of cured resin reached 30.2% with the content of phosphorus only 0.67 wt%, in which the weight ratio between DGEBDB and DGEBA was 1:9 (B1D9/DDM). When the weight ratio of DGEBDB to DGEBA was further increased to 2:8 for the B2D8/DDM system, the UL-94 V-0 grade was achieved. Meanwhile, the mechanism of DGEBDB in improving the flame retardancy of cured resin was discussed and revealed. This easily available and eco-friendly DGEBDB was proved to be a highly efficient reactive flame retardant for epoxy resin. • A high-efficient flame retardant for epoxy was synthesized from the renewable resource. • Guaiacol acted as both reactant and solvent, it could be recycled and re-used. • The flame retardant showed very good compatibility with DGEBA. • UL-94 V0 grade epoxy was achieved with the phosphorus content was only 1.27%. [ABSTRACT FROM AUTHOR]