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Intrinsic flammability significantly impedes practical applications of epoxy (EP), despite many merits. Intercalation‐functionalized graphene oxide (GO) has shown excellent performance in flame retardancy studies of polymers, but research investigating the effect of layer spacing on the flame‐retardant performance of polymers is still lacking so far. Therefore, three GO flame retardants with different layer spacing were prepared to flame retardant EP. When the layer spacing of GO is 1.09 nm, the heat and smoke release from EP composites is effectively suppressed. This is attributed to the barrier effect and maze effect of GO as well as the synergistic effect between the intercalator and GO. Analysis shows that the layer spacing of GO affects the flame retardancy of the composite by influencing the formation of protective char layer. [ABSTRACT FROM AUTHOR]

• A peculiar preparation method of bio-based self-healing/recyclable polyurethane: the raw materials come from cheap plant spices, dairy products and oils. The raw materials meet the requirements of sustainability. • A Combination of two different thermally reversible mechanism (deblocking/re-blocking of phenolic urethanes and imines metathesis) are introduced into the same system, thereby improving self-healing ability and recyclability. • The role of the non-toxic crosslinking agent triethanolamine (TEOA) was discussed. TEOA can promote bonding of phenolic urethanes. Even though HDI itself is low in activity, the lone pair of electrons provided by TEOA can guarantee the rapid reorganization of the cross-linked network. • Efficient self-healing/reprocessing reduces material waste. All the original properties of the material are preserved to the greatest extent. Bio-based, healable, and recyclable polyurethane materials conform to the sustainability of the polyurethane industry. By introducing dynamic covalent bonds, the cross-linked polyurethane can obtain the performance of network rearrangement, thereby realizing self-healing and reprocessing. In this work, a self-healing/renewable polyurethane based on bio-based vanillin and tyrosine was successfully synthesized solvent-freely and catalysts-freely. Due to two different thermal reversible mechanisms, metathesis of imines and deblocking/re-blocking of phenolic urethanes, the obtained PU has considerable self-healing efficiency and renewability. At 120 °C, the surface scratches almost completely disappear within 90 min, and the tensile strength can be restored to ∼ 95% within 2 h. After remolded for 5 times, the chemical structure, glass transition temperature, deblocking behavior, tensile strength, elongation at break and gel content didn't change significantly. Both the environmental friendliness of bio-based raw materials and the renewability of the obtained polyurethane materials meet the requirements of sustainability. [ABSTRACT FROM AUTHOR]

The requirements for long-term stability and thermal performance of resin-based coating materials are gradually increasing with the development of aerospace industry. As a low-toxicity aldehyde, terephthalaldehyde (TPA) with aromatic ring structure and high reactivity is an ideal formaldehyde substitute for synthesizing high thermal stability phenolic resins and coating candidate. In this work we provided a strategy for the synthesis of ferrocenecarboxaldehyde (Fc) in-situ modified TPA-phenol resin (PTPA-Fc), obtaining resin products with high glass transition temperatures at 302 °C. The non-isothermal curing process and activation energy changes of resins with different TPA-phenol ratios were further investigated. It was found that the highest cross-linking density of resin was achieved when TPA/phenol was 0.5, with the initial decomposition temperature (T 5%) reached 378 °C. Afterwards, carbonyl iron powder (CIP) filled PTPA-Fc microwave absorbing coating was prepared. Due to the improved oxidation resistance, composite based on PTPA-Fc had an effective bandwidth of 3.1 GHz (14.5–17.6 GHz, thickness 3 mm) after 100 h heat treatment at 250 °C and could still cover the 9.5–18 GHz absorption band (with RL ≤ -5 dB) with 5 mm matching thickness, reflecting a good long-term thermal stability. [Display omitted] • A strategy for the synthesis of ferrocenecarboxaldehyde (Fc) in-situ modified TPA-phenol resin (PTPA-Fc) was provided. • PTPA-Fc exhibited outstanding thermal properties, with a Tg of 302 °C, a T 5% of 378 °C and a pyrolysis yield of 69.7 % at 800 °C. • CIP-PTPA-Fc with excellent long-term oxygen-thermal stability could effectively protected CIP absorber from oxidation. • CIP-PTPA-Fc coating had an effective bandwidth of 3.1 GHz after 100 h heat treatment (250 °C). [ABSTRACT FROM AUTHOR]

• NaOH and trisilanolphenyl polyhedral oligomeric silsesquioxane (TPOSS) were used as catalysts to synthesize a novel boron-containing phenolic resin (TBPR). • NaOH/TPOSS results in more para -methylene linkage in TBPR structure, which is the key to the remarkable initial decomposition temperature. • The morphological transformation of TBPR at different temperatures was studied to verify the role of Si and B on the thermal pyrolysis stability. • CF/TBPR shows an outstanding ablative resistance due to the remakable thermal stability of TBPR. The heat resistance of existing phenolic resins cannot meet the requirements of the increasingly harsh spaceflight environment. Boron and silicon have been added to phenolic resins to improve the char yields. However, achieving both a high initial decomposition temperature and an outstanding char yield remains challenging. This study presented a strategy to regulate the methylene types of boron-containing phenolic resin (TBPR) by trisilanolphenyl polyhedral oligomeric silsesquioxane (TPOSS) and NaOH. Thermogravimetric analysis (TGA) in nitrogen of cured TBPR displayed remarkable thermal stability with an initial decomposition temperature of 450.0 °C and a char yield of 75.8 %. The effect of TPOSS and NaOH on the TBPR structure were further investigated using nuclear magnetic resonance (NMR) analysis and density functional theory (DFT) calculation. The results indicated that TPOSS could attract sodium phenate and formaldehyde through hydrogen bonds, and greatly reduced the energy barrier of the phenol–formaldehyde resin para -addition. The formation of more p-p' type methylene structures of phenolic resin profoundly contributed to the outstanding initial decomposition temperatures and char yield. TBPR matrix transformed into a stronger protective char layer, forming an effective thermal protection barrier. As a result, the mechanical strength and ablative resistance of the fiber-reinforced CF/TBPR composites were enhanced by the excellent thermal stability of TBPR matrix. [ABSTRACT FROM AUTHOR]