Most organic polymeric materials have high flammability, for which the large amounts of smoke, toxic gases, heat, and melt drips produced during their burning cause immeasurable damages to human life ...and property every year. Despite some desirable results having been achieved by conventional flame‐retardant methods, their application is encountering more and more difficulties with the ever‐increasing high flame‐retardant requirements such as high flame‐retardant efficiency, great persistence, low release of heat, smoke, and toxic gases, and more importantly not deteriorating or even enhancing the overall properties of polymers. Under such condition, some advanced flame‐retardant methods have been developed in the past years based on “all‐in‐one” intumescence, nanotechnology, in situ reinforcement, intrinsic char formation, plasma treatment, biomimetic coatings, etc., which have provided potential solutions to the dilemma of conventional flame‐retardant methods. This review briefly outlines the development, application, and problems of conventional flame‐retardant methods, including bulk‐additive, bulk‐copolymerization, and surface treatment, and focuses on the raise, development, and potential application of advanced flame‐retardant methods. The future development of flame‐retardant methods is further discussed.
Flame‐retardant methods for polymeric materials are reviewed with particular focus on advanced flame‐retardant methods developed in recent years. Both the advantages and drawbacks of these methods are discussed, and prospects for the future development of flame‐retardant methods are presented. It is hoped that this review will guide the development of flame‐retardant polymeric materials.
We investigated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) environmental contamination in 2 rooms of a quarantine hotel after 2 presymptomatic persons who stayed there were ...laboratory-confirmed as having coronavirus disease. We detected SARS-CoV-2 RNA on 8 (36%) of 22 surfaces, as well as on the pillow cover, sheet, and duvet cover.
The energy performance in buildings is influenced by many factors, such as ambient weather conditions, building structure and characteristics, the operation of sub-level components like lighting and ...HVAC systems, occupancy and their behavior. This complex situation makes it very difficult to accurately implement the prediction of building energy consumption. This paper reviews recently developed models for solving this problem, which include elaborate and simplified engineering methods, statistical methods and artificial intelligence methods. Previous research work concerning these models and relevant applications are introduced. Based on the analysis of previous work, further prospects are proposed for additional research reference.
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•A new P/Cu-hybrid silica aerogel is developed for flame-retarding and smoke-suppressing polyurethane foam.•The aerogel-containing composite foam has greatly improved thermal ...insulation.•The incorporation of the aerogel realizes the improvement of compressive strength of the composite foam.•The multiple synergistic of the aerogel enables the composite foam with flame retardancy and smoke suppression.
The frequent occurrence of fires caused by rigid polyurethane foam highlights the importance of its fire safety, however, the existing flame-retardant methods often seriously deteriorate the mechanical properties and thermal insulation of the foam. Here, we demonstrate a new idea for thermal insulation, flame retardancy, smoke suppression, and reinforcement of polyurethane foams only by incorporating a P/Cu-hybrid silica aerogel. This unique aerogel combines with the carbon-promoting action of P, catalytic attenuation of Cu, and the barrier effect of aerogels, thus leading to high smoke-suppressing and flame-retardant efficiency for polyurethane foam. At a low addition amount of 5 wt% aerogel, the total heat release, peak heat release rate, total smoke release, and toxic CO production of the composite foam are all significantly reduced. Interestingly, the aerogel-containing composite foam exhibits a special hierarchical porous structure, which enables lower thermal conductivity and higher thermal insulation than pure RPUF. Benefitting from the good compatibility and nano-enhancing effect of the aerogel, the compressive strength of the composite foam remarkable increase of 52.2%. This research offers an effective method for designing high-performance foam materials with high fire safety and low thermal conductivity, which has broad application prospects in the field of thermal insulation.
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•The combination of the inorganic structure with the flexible aliphatic segment was proposed to fabricate P-decorated POSS.•Epoxy resins with P-decorated POSS maintained high ...transparency.•The resultant P-decorated POSS showed both high flame retardancy and mechanical reinforcement for epoxy resins.•The specific mechanism of action was analyzed.
Epoxy resins (EPs) are known for their durability, strength, and adhesive properties, which make them a versatile and popular material for use in a variety of applications, including chemical anticorrosion, small electronic devices, etc. However, EP is highly flammable due to its chemical nature. In this study, phosphorus-containing organic–inorganic hybrid flame retardant (APOP) was synthesized by introducing 9, 10-dihydro-9-oxa-10‑phosphaphenathrene (DOPO) into cage-like octaminopropyl silsesquioxane (OA-POSS) via Schiff base reaction. The improved flame retardancy of EP was achieved by combining the physical barrier of inorganic Si-O-Si with the flame-retardant capability of phosphaphenanthrene. EP composites containing 3 wt% APOP passed the V-1 rating with a value of LOI of 30.1% and showed an apparent reduction in smoke release. Additionally, the combination of the inorganic structure and the flexible aliphatic segment in the hybrid flame retardant provides EP with molecular reinforcement, while the abundance of amino groups facilitates a good interface compatibility and outstanding transparency. Accordingly, EP containing 3 wt% APOP increased in tensile strength, impact strength, and flexural strength by 66.0 %, 78.6 %, and 32.3 %, respectively. The EP/APOP composites had a bending angle lower than 90°, and their successful transition to a tough material highlights the potential of this innovative combination of the inorganic structure and the flexible aliphatic segment. In addition, the relevant flame-retardant mechanism revealed that the APOP promoted the formation of a hybrid char layer containing P/N/Si for EP and produced phosphorus-containing fragments during combustion, showing flame-retardant effects in both condensed and vapor phases. This research offers innovative solutions for reconciling flame retardancy & mechanical performances and strength & toughness for polymers.
Poly(ethylene terephthalate) (PET) is a fiber‐forming polymer with the largest output and widest usage. Its flame retardation is well‐achieved via a mechanism of promoting the melt dripping while ...ignited. However, the melt dripping leads to secondary damage and an immediate empyrosis during fire. How to address the contradiction between the flame retardation and the melt‐dripping behavior of PET via an inherent flame‐retardant approach becomes a real challenge. This feature article highlights the design and synthesis of novel PET‐based copolyesters with flame‐retardant and antidripping performance. Three approaches are used to design these copolyesters: “ionic aggregation,” “smart self‐cross‐linking,” and “rearrangement at high temperatures.” Some new conceptions are proposed accordingly. The synthesis, structure characterization, and properties of those copolyesters are discussed together with the ongoing challenges and limitations at this frontier.
A contradiction between the flammability and melt‐dripping problems for poly(ethylene terephthalate) (PET)‐based copolyesters has puzzled the flame‐retardant field for many years. Traditional, inherently flame‐retardant technologies of PET cannot resolve its melt‐dripping problem. In this feature article, how to design and synthesize novel PET‐based copolyesters with flame‐retardant and antidripping performance is highlighted and discussed.
Path planning is essential for robots to efficiently execute jobs in challenging settings. In this paper, we propose a new algorithm, called potential function-based sampling heuristic optimal path ...planning considering congestion (CCPF-RRT*), extending the standard Rapidly-exploring Random Tree star (RRT*) to address the issues of slow convergence, high path cost, and how to plan suitable paths in the presence of congested regions in the environment. First, the CCPF-RRT* algorithm adds the artificial potential field to RRT*, which can drastically cut down on the number of iterations and speed up convergence. Second, a movement cost function that takes congestion intensity and path length into account when evaluating a connection between two path nodes is created. This function is then used to direct the growth of new nodes and the updating of parent nodes so that the algorithm takes congestion intensity and path length into account when generating paths. Third, in order to reduce the path cost, the algorithm establishes parent nodes for random nodes by combining the benefits of the F-RRT* algorithm. The movement cost function is added to the process of establishing parent nodes to optimize the path cost in order to prevent the creation of parent nodes that force the path to traverse through crowded areas. In experimental simulation results, the algorithm outperforms RRT*, Q-RRT*, PQ-RRT*, and F-RRT* not only in terms of initial solution and quick convergence speed, but is also able to design an ideal path with the lowest movement cost in a crowded environment using the movement cost function.
An efficient palladium‐catalyzed Heck‐type reaction of fluoroalkyl halides, including perfluoroalkyl bromides, trifluoromethyl iodides, and difluoroalkyl bromides, has been developed. The reaction ...proceeds under mild reaction conditions with high efficiency and broad substrate scope, and provides a general and straightforward access to fluoroalkylated alkenes which are of interest in life and material sciences.
Simplicity is beauty: The title reaction features a broad substrate scope and excellent functional‐group compatibility. Mechanistic studies reveal that the free fluoroalkyl radicals initiated by Pd0Ln through a single‐electron transfer pathway is involved in the Heck‐type catalytic cycle.
By using the Hirota bilinear form of the KP equation, twelve classes of lump–kink solutions are presented under the help of symbolic computations with Maple. Analyticity is naturally achieved by ...taking special choices of the involved parameters to guarantee a positive constant term. A key step in generating lump–kink solutions is to combine quadratic functions and the exponential function in the second-order logarithmic derivative transformation.
High‐performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their ...applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo‐responsive self‐ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high‐strength semi‐crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several‐fold (from 0.739 to 2.726 MPa). The self‐ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self‐ceramifiable capacity enables aerogels to provide fire resistance, high‐strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack‐free overall structure, and invariant porous morphology. This self‐ceramifiable aerogel opens up a new avenue for developing thermal‐protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments.
A new thermo‐responsive self‐ceramifiable aerogel is for the first time reported with exceptional strengthening and thermal insulation at high temperatures. Under normal conditions, the aerogel exhibits excellent toughness and machinability. Upon exposure to high temperatures, the aerogel spontaneously and rapidly transforms into robust semi‐crystalline hard ceramics, thus leading to fire resistance, high strength, and thermal insulation in extreme environments.
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