Unsaturated polyester resins (UPR) are commonly used in electronics manufacturing and traditional construction, but their inherent flammability greatly limits their use. An expansive flame retardant EZ was prepared via the simple ionic reaction between the 2-Aminothiazole (AMZ) and ethylene diamine tetra methylene phosphoric acid (EDTMP). The thermal decomposition process of EZ and UPR/EZ and the flame retardancy of the compound were studied. The flame retardancy mechanism of EZ in UPR was analyzed in detail. When the EZ content was 15 wt%, the flame-retardant grade of the composite reached V-0. The flame-retardant efficiency was very high mainly through the interaction of gas phase and condensed phase. Interestingly, flame retardant EZ can perform expansion crosslinking in UPR, which can effectively promote carbon formation in UPR. Moreover, EZ itself can also expand to form dense and continuous carbon layers in UPR, which further elucidates the flame-retardant mechanism.

A biomass intumescent flame retardant (TA-g-DOPO) was fabricated from tannic acid (TA) and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) through the bridge of silane coupling agent (KH560), which showed a low degradation rate at Tmax of 2.71 %/min and a high char yield of 55.8%. Then, various EP composites with 4∼10 % TA-g-DOPO were prepared. Due to the presence of flexible silane structures and rigid phosphaphenanthrene rings as well as the remained phenol groups (tending to form hydrogen bonds with epoxy matrix), EP composite with a high content of 10% TA-g-DOPO exhibited no deterioration on the tensile and impact properties as well as the glass transition temperature (Tg) when compared with pure EP. More importantly, it reached a high LOI value of 30.3% and passed a V-0 rating in the UL-94 burning test. Additionally, its peak heat release rate (PHRR), total heat release (THR) and average mass loss rate (av-MLR) decreased by 23.2%, 15.5% and 30.2% respectively. Analyses from the condensed char and pyrolysis gases indicated that the improved flame retardancy was mainly attributed to the cooperation of the free-radical quenching effect of P-containing radicals and phenoxy radicals working in stages (derived from DOPO and TA respectively) and the physical barrier effect caused by the highly graphited, intumescent and porous char layer (reinforced by P- and Si-containing cross-linked structures). This work provides a sustainable biomass flame retardant with good flame-retarding efficiency based on TA.

Novel 2D materials are now at the forefront of developing advanced multifunctional composite film due to their fascinating properties. Particularly, graphene and MXene-based 2D materials are regarded as potential multifunctional materials for structure–function and integration with laminated composites. As expected, high mass production from low-cost and facile fabrication techniques for multifunctional composites film plays a pivotal role in their practical applications. Herein, we have covered a broad spectrum of 2D materials overview, covering all contributions to this field and summarizing the most pertinent literature available for developing multifunctional composites which are attractive for advanced aircraft applications. Moreover, the integrated functions of the 2D materials-based multifunctional composites such as sensing and actuation behaviour, thermal conductivity, and electromagnetic interference (EMI) shielding effectiveness are explored and their mechanism for superior performance is detailed. Some prevailing challenges with perspectives of this thriving field have also been critically discussed.

Polyester-cotton fabrics (PTCO) have excellent properties and are ubiquitous in daily life, but their serious flammability brings great safety hazards to people's lives. This study used phenylphosphonic acid (PPOA) and urea as raw materials to prepare a flame retardant named POU. PTCO/POU was prepared by the pad-dry-cure technique, and the performance was compared with that of PTCO/PPOA, revealing many interesting phenomena. Based on the gas phase and condensed phase flame-retardant mechanism brought by P/N synergy, PTCO/POU had better flame retardancy than PTCO/PPOA did. The damaged length was 6.7 cm, and the limiting oxygen index (LOI) value was 30.1%. The char residues after burning were complete and denser with a higher degree of graphitization. Thermogravimetric analysis showed that POU can significantly reduce the Rmax of PTCO, and improve its thermal stability in high temperature zones. The CCT results showed that PTCO/POU had the longest time to ignition and the smallest fire growth index, which was of great significance for reducing fire risk. The TG-FTIR results showed that the volatile products of PTCO/POU were greatly reduced, and during the burning process, NH3 was produced to dilute the concentration of combustible gases. In addition, PTCO/POU also had better whiteness performance than PTCO/PPOA did. This work greatly improved the flame retardancy of PTCO in a simple way and expanded its application prospects.

To address the shortcomings of traditional intumescent flame retardants (IFRs), a novel four-in-one IFR (M[APP/NiCo2O4]) was constructed for the first time. It integrates acid source, gas source, carbon source (crosslinking β-CD), and synergistic agent (NiCo2O4 nanoparticles) into a single entity by a co-encapsulation technology. Under the loading of 20 wt.%, its flame retardant performance was significantly better than that of simple mixed flame retardants, and it could increase the limiting oxygen index of polypropylene (PP) from 18 to 30.2 and pass the UL-94 V-0 rating. At the same time, it could reduce the peak of heat release rate, total heat release, and peak of CO production of PP by 77%, 22%, and 80%, respectively, showing excellent flame retardant performance. The excellent flame retardant performance is mainly because the synergist NiCo2O4 nanoparticles in the four-in-one flame retardant can easily combine and efficiently interact with the acid source, carbon source, and gas source in the intumescent flame retardant to form a more stable protective char residue. In addition, the crosslinking β-CD shell enhances both the water resistance and initial thermal decomposition temperature of PP containing the four-in-one IFR compared to PP with simple mixed control samples. After 72 hours of water resistance test, it can still maintain the UL-94 V-0 rating. The presence of the crosslinking β-CD shell also improves the compatibility of the four-in-one flame retardant in PP, and its adverse effects on the mechanical properties of PP are also significantly smaller than those of the mixed control sample.

This investigation focuses on the synergistic performance improvement in graphene/MWCNT reinforced Polyaryletherketone (PAEK) - carbon fiber (CF) multi-scale composites. FTIR revealed the chemical interactions while HRTEM, XRD and 3D X-ray microscopy gave insight into nanofiller dispersion and microstructural features. The functional groups on nanofillers along with structural features integrated various components of the multi-scale composites by formation of graphene/MWCNT/CF complex network that provided larger interfacial area, bridging effect and physico-chemical interaction with PAEK while restricting its segmental mobility. Multi-scale composites displayed significantly improved strength, fracture toughness, interlaminar shear strength, glass transition temperature and tribological performance. Under dynamic load, graphene/MWCNT reinforcement of matrix and CF synergistically increases the storage modulus and energy absorption characteristics. Wear and fracture surface morphology of nano and multi-scale composites showed ductile failure confirming interfacial adhesion. The failure behavior in experimental studies was supported by Abaqus/Explicit-based FEM models of fracture toughness response. This work provides a promising avenue to develop next generation high performance thermoplastic composites for structural applications.

The substitutional structure of cyclotriphosphazene derivatives significantly influences their flame-retardant effectiveness. A cyclotriphosphazene derivative with triazole group, referred to as hexa(1,2,4-triazol-3-ylamine) cyclotriphosphazene (HATA), was utilized to improve the flame retardancy of epoxy resin (EP). Differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis were employed to characterize the thermal properties of EP/HATA thermosets. HATA facilitated the curing of EP due to its triazole and secondary amine structure. EP/HATA thermosets exhibited improved char-forming ability and storage modulus, attributed to the rigid cyclophosphonitrile structure of HATA. As a result of incorporating 5% HATA with 0.73 wt% phosphorus, EP passed UL-94 V-0 level. Subsequent analysis using a cone calorimeter revealed obvious reductions in the peak heat release rate, fire growth rate, and total smoke production of EP with the addition of HATA. Simultaneously, there was a significant enhancement in the char yield of EP during combustion, indicating notable improvements in fire safety. Additional investigations, including X-ray photoelectron spectroscopy, scanning electron microscopy, TG-FTIR, and pyrolysis gas chromatography/mass spectrometry, were employed to analyze the char residue and gaseous volatiles. HATA promoted the formation of a dense, continuous, and intumescent char layer containing cyclophosphonitrile structure in EP. Moreover, the decomposition of HATA released a notable quantity of nitrogen-containing volatiles, effectively mitigating flammable gases originating from the EP matrix in gaseous phase. A biphasic flame-retardant mode of action was proposed, underscoring cooperative flame-retardant effects arising from the interaction between triazole substituents and cyclophosphonitrile structure in HATA molecular for EP.

Asphalt pavement is widely applied to the surface in high-grade highway tunnels due to its prominent preponderance in road performance. However, asphalt is flammable as the binder material to adhere the aggregates and other additives, resulting that a fire in the semi-closed space of the tunnel can ignite and burn asphalt pavement to generate a large amount of heat and smoke. Therefore, further promoting the advance of flame-retardant asphalt pavement is essential to ensure security in tunnels. We gathered the relevant standards or regulations of diverse nations and test methods concerning flame retardancy of asphalt. Then we reviewed the research status of flame-retardant asphalt mixture, including thermal characteristics of the asphalt and four fractions, the flame retardants applicable to asphalt, and effects on other components. This review demonstrated that establishing universal standards and test methods is a research basis specifically for flame-retardant asphalt pavement. To optimize the flame retardancy of asphalt pavement, it should focus on the synergy with diversified aspects such as asphalt binders, multiple flame retardants, aggregates, mineral powders, fibers, and other additives.

Understanding the external and internal factors during an additive manufacturing (AM) process is crucial, as they can significantly affect the final product's performance. Efforts have been made to unwind the product, process, property, and performance (PPPP) relationships. The conventional experimental approaches can lead to boundless runs, resulting in exorbitant costs for research and development. Hence, developing, adapting, and validating numerical models is essential to achieving the desired performance of 3D-printed products with lesser resource utilization. In this study, numerical and experimental techniques were used to perform the PPPP relationship assessment on material extrusion 3D-printed parts. Three infill designs (rectangular, triangular, and hexagonal), with layer heights (0.1 mm, 0.125 mm, and 0.2 mm), and three different materials (carbon fiber-reinforced polyamide-6 (PA6-CF), polyamide-6 (PA6), and acrylonitrile butadiene styrene (ABS)), were selected for the investigation. Taguchi's design of experiments (DOE) method was used to limit the number of numerical simulations and experimental runs. A thermomechanical numerical model was utilized to perform the material extrusion process simulations and mechanical performance prediction of the specimens. Subsequently, the samples were 3D-printed and tested mechanically to validate the numerical simulation results. The dimensional, distortion, and mechanical analysis performed on numerical simulation results agreed well with the experimental observations.

Injection moulded specimens were produced from biodegradable poly(butylene succinate) (PBS)/organomodified montmorillonite (OMMT) nanocomposites, after melt compounding in different compositions. WAXD studies demonstrated that the OMMT formed similar intercalation levels in the 2.5–10 w/w% additive ratio range. It was also proved by rotational rheometry that the nanoclay stacks form physical network above 5 w/w% concentration, which significantly influence the viscoelastic properties of the melt. The value of zero shear viscosity also changed accordingly, starting to increase above 5 w/w% nanoclay content. The OMMT content reduced the creep sensitivity measured in molten state.X-ray and DSC investigations showed that OMMT inhibits the crystallisation of PBS, resulting in a decrease in crystallinity at higher nanoclay ratios. As a result, the room temperature creep increased with the OMMT ratio.The Young's modulus linearly increases in the entire concentration range exceeding 1.2 GPa at 10 w/w% nanoclay content. The value of yield strength does not change significantly (35–40 MPa), but the strain at yield – which characterises stiffness – and the notched Izod impact strength already decrease at 2.5 w/w% OMMT content, but further increasing the nanoclay content has minor effect. However, the nanocomposite with 10 w/w% OMMT can be a real alternative to polypropylene (PP) and high-density polyethylene (HDPE) injection moulded products based on its mechanical properties.To characterise the effect of OMMT on dynamic mechanical properties, the S (Stiffening effectiveness), L (Loss effectiveness) and D (Damping effectiveness) indices were introduced to quantitatively describe the nanoclay effect intensity in each temperature range.