The fire detection plays a critical role in the maintenance of public security. Previous approaches of early fire warning, based on smoke or temperature response must be set in the proximity of a ...fire. They cannot provide the additional information of fire location or size and are susceptible to complicated situations. It is still a big challenge to make rapid and accurate early fire warning in precombustion because of the lack of reliable alarm signals. Herein, a precursor molecular sensor (PMS) is designed and synthesized that can present the chemical structure transformation to form phthalocyanines (Pcs) and release a color change signal at about 180 °C, learning from the plant chlorophyll metabolism. Further, the PMS is assembled to an early fire warning component (EWC) and an intelligent image recognition algorithm is introduced for unburned fire detection. The EWC generates a colorful alarm within 20 s at 275 °C. Therefore, the facile PMS provides a reliable real‐time monitoring strategy to the early fire warning detection in precombustion.
A bioinspired color changing molecular sensor is designed to achieve early fire detection based on transformation of phthalonitrile to phthalocyanine, learning from the plant chlorophyll metabolism. An intelligent image recognition algorithm is applied and the sensor generates colorful alarm within 20 s at 275 °C. This study provides a reliable real‐time monitoring strategy to the early fire detection in precombustion.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire‐safety ...properties, thus restricting their applications. Reported herein is an end‐group‐capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N‐(2‐hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl‐terminated fragments, thus increasing the fire‐safety properties, such as self‐extinguishing, anti‐dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi‐aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire‐safe polymers.
Captured: End‐group capture of benzoxazole from the thermal rearrangement of a hydroxy‐containing phthalimide group contributes to the fire‐safety features of polyesters. This novel strategy exhibits applicability and efficiency for both semi‐aromatic and aliphatic polyesters, providing a new design approach to fire‐safe polymers.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Although a variety of dynamic covalent bonds have been successfully used in the development of diverse sustainable thermosetting polymers and their composites, solving the trade‐off between recovery ...efficiency and comprehensive properties is still a major challenge. Herein, a “one‐stone‐two‐birds” strategy of lower rotational energy barrier (Er) phosphate‐derived Diels–Alder (DA) cycloadditions was proposed for easily recyclable carbon fiber (CF)‐reinforced epoxy resins (EPs) composites. In such a strategy, the phosphate spacer with lower Er accelerated the segmental mobility and dynamic DA exchange reaction for network rearrangement to achieve high‐efficiency repairing, reprocessing of the EPs matrix and its composites and rapid nondestructive recycling of CF; meanwhile, incorporating phosphorus‐based units especially reduced their fire hazards. The resulting materials simultaneously showed excellent thermal/mechanical properties, superb fire safety and facile recyclability, realizing the concept of recycling for high‐performance thermosetting polymers and composites. This strategy is of great significance for understanding and enriching the molecular connotation of DA chemistry, making it potentially applicable to the design and development of a wide range of dynamic covalent adaptable materials toward practical cutting‐edge‐tech applications.
A strategy of tailoring dynamic covalent bonds with a low rotational energy barrier was proposed to fabricate phosphate‐derived Diels–Alder crosslinked recyclable thermosets and their composites, simultaneously overcoming the trade‐off between recycling efficiency and comprehensive properties in current covalent adaptable materials and offering a guidance for the rational design of sustainable thermosetting polymers for versatile applications.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Recent advances in epoxy resins have been forward to achieving high mechanical performance, thermal stability, and flame retardancy. However, seeking sustainable bio-based epoxy precursors and ...avoiding introduction of additional flame-retardant agents are still of increasing demand. Here we report the synthesis of p-hydroxycinnamic acid-derived epoxy monomer (HCA-EP) via a simple one-step reaction, and the HCA-EP can be cured with 4,4′-diaminodiphenylmethane (DDM) to prepare epoxy resins. Compared with the typical petroleum-based epoxy resin, bisphenol A epoxy resin, the HCA-EP-DDM shows a relatively high glass transition temperature (192.9 °C) and impressive mechanical properties (tensile strength of 98.3 MPa and flexural strength of 158.9 MPa). Furthermore, the HCA-EP-DDM passes the V-1 flammability rating in UL-94 test and presents the limiting oxygen index of 32.6%. Notably, its char yield is as high as 31.6% under N2, and the peak heat rate release is 60% lower than that of bisphenol A epoxy resin. Such findings provide a simple way of using p-hydroxycinnamic acid instead of bisphenol A to construct high-performance bio-based thermosets.
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A novel bio-based monomer, HCA-EP, with low viscosity is synthesized and used to prepare an epoxy resin having low flammability, high Tg and mechanical properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Novel flame-retardant bio-based long-chain aliphatic polyamide with great overall properties.•The copolymer exhibited high LOI value of 32.6%, and achieved an UL-94 V-0 rating.•Successful inhibition ...of the release of heat and toxic gasses in cone calorimetry test.•The copolymer showed largely improved tg and maintained thermal and mechanical properties.
Bio-based long-chain aliphatic polyamides show remarkable potential in pursuing high-performance, sustainable bio-plastics. However, the aliphatic structure also leads to high flammability that severely restricts their applications. Herein, we demonstrate a novel flame-retardant system to fabricate high-performance, flame-retardant bio-based long-chain aliphatic polyamide. In this system, a novel reactive nitrogen-based flame-retardant monomer, PDB, was designed and synthesized. Subsequently, the corresponding bio-based long-chain polyamide copolymer was prepared through a facile polycondensation process. The nitrogen-based groups exhibited highly efficient free-radical-capturing effect, helping the copolymer achieve a high limiting oxygen index value of 32.6%, the UL-94 V-0 rating, a 33.3% lower peak heat release rate, and inhibited the release of toxic gasses at a PDB content of 6 wt%. Furthermore, the copolymer exhibited largely maintained crystallinity, thermal stability, and mechanical properties, owing to the high reactivity of PBD with polyamide monomers. At the same time, the incorporation of PBD increased the rigidity of the copolymer, resulting in a significant increase of 16.4 °C in the glass transition temperature and lower dielectric properties. This work provides a new perspective on the preparation of bio-based long-chain aliphatic polyamide with enhanced overall properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Wood is an important renewable material exhibiting excellent physical and mechanical properties, environmental friendliness, and sustainability, and has been widely applied in daily life. However, ...its inherent flammability and susceptibility to fungal attack greatly limit its application in many areas. Use of fire-retardant coatings and preservatives has endowed wood with improved safety performance; importantly, the cooperative effect of dual treatments on the burning behavior and flame retardancy of wood needs to be better understood. Here, a two-step treatment for wood is proposed, with a copper–boron preservative (CBP) and a fire-retardant coating. The thermal degradation and burning behavior of treated wood were investigated. The CBP formed a physical barrier on the wood surface, facilitating a charring process at high temperatures and thus suppressing the release of heat and smoke. Notably, the dual-treated wood exhibited lower heat release and reduced smoke emission compared with the mono-treated wood, indicating a cooperative effect between CBP and fire-retardant coatings, beneficial to the improvement of fire safety. This experimental work improved fire retardance and suppressed smoke release in flammable materials, and offers a new design for developing fire-retardant coatings.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ultra-low dielectric loss (Df) and low dielectric constant (Dk) materials are urgently required in high-speed and large-capacity transmission, in which the wholly aromatic liquid crystal polymer ...(LCP) has gained attention due to its excellent dielectric properties. However, the relationship between molecular structure and dielectric properties is still not clear. In this study, two copolyesters containing phenyl or naphthyl structures are synthesized, as well as the effects of benzene and naphthalene mesogens on dielectric properties are investigated. The synthesized copolyesters containing naphthalene structure have good comprehensive properties with high thermal stability (T5% = 479 °C and Tg = 195–216 °C), inherent flame retardance (LOI = 33.0–35.0 and UL-94 V-0 level at 0.8 mm), low Dk (2.9–3.0@10 GHz) and low Df (0.0027–0.0047@10 GHz). Naphthalene mesogen can reduce the dielectric loss more significantly than benzene at high frequency by reducing the density and mobility of polarizable groups, which leads to the effectively limited dipole polarization in copolyesters. Consequently, we proposed a new strategy for designing low Dk and low Df materials.
This study proposes a new strategy for designing liquid crystal polymer materials with low dielectric constant and low dielectric loss at high frequency. Display omitted
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Since cable insulation with low thermal conductivity occupies a large proportion of high-voltage cable, an optimization analysis on dynamic thermal behavior of cable insulation can be very useful to ...improve the accuracy of cable dynamic thermal rating. In this paper, the dynamic thermal analysis of cable insulation is carried out by combining the theoretical method and finite-element analysis (FEA) method. Based on the analysis, it is proved that using IEC recommended transient thermal model of cable insulation will bring certain error to cable dynamic temperature evaluation, especially at the early stage of cable temperature rise. Moreover, in this paper, an implementable optimization method for transient thermal model of cable insulation is developed. The improvement of the optimized model compared with the IEC model on cable dynamic thermal rating is verified by the FEA method. The results confirm that the optimized model can better model the dynamic thermal behavior of cable than the IEC model and the improvement is more obvious for dynamic thermal rating of cable with high voltage level and under large load. The methodology developed in this paper can pave a way for electricity utilities to increase cable utilization while still ensuring cable reliability.
•A multifunctional additive was successfully synthesized through a one-pot route.•The resultant thermoset EP-DPI exhibited excellent comprehensive properties.•High flame retardancy was realized at a ...low DPI and phosphorus content.•The toughening and flame-retardant mechanism were revealed in detail.
High-performance and multifunctional epoxy resins (EPs) are of great use in the booming electric & electronic and 5G fields, however their fabrication shows huge challenges. Herein, through a facile strategy by simply incorporating a functional molecule DPI (phosphaphenanthrene polyethylenimine), which possessed a unique structure with hyperbranched polyethyleneimine as flexible inner core and phosphaphenanthrene groups as rigid outer shell, a high-performance and multifunctional epoxy resin was successfully fabricated. The hyperbranched rigid-flexible structure of DPI endowed the resultant thermoset EP-DPI with superb mechanical performance and high glass transition temperature, for which, at a low DPI content (≤4 wt%), EP-DPI exhibited 160%, 40%, and 31% improvement in impact toughness, tensile strength, and flexural strength compared with neat EP. At the same time, the good compatibility between DPI and the EP matrix enabled EP-DPI to be highly transparent, and the aromatic phosphorus structure endowed EP-DPI with excellent UV-shielding effect in the UV-A band. The dielectric performance of EP-DPI was enhanced due to the unique structure of DPI and its interaction with the EP matrix. Furthermore, the phosphaphenanthrene groups endowed EP-DPI with excellent anti-ignition, self-extinguishing, and low heat release during combustion. This work opens up a new strategy for developing novel high-performance and multifunctional EPs with potential versatile applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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