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Special Issue "New Prospects in Flame-Retardant Materials"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Materials Chemistry".

Deadline for manuscript submissions: closed (15 February 2022) | Viewed by 9069

Special Issue Editor

Dr. Anthony Chun Yin Yuen
E-Mail Website
Guest Editor
School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney 2052, Australia
Interests: computational fluid dynamics; computational heat transfer; heat and mass transfer operations; composite materials; fire management; simulation and modelling; composite and hybrid materials; artificial intelligence
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Lightweight, high-performance composite materials, such as fibre-reinforced polymers, are rapidly replacing conventional building materials. Nevertheless, these polymeric materials are often associated with life-threatening fire hazards due to the production of toxic substances in the event of fires. Fire incidents caused by these highly flammable polymers have increased dramatically over the last decade. Therefore, it is common nowadays to add nanofillers to the polymer matrix as flame retardants to effectively reduce the flammability, asphyxiated gases and generation of smoke. Recent studies on bio-inspired flame retardants have achieved remarkable flame-retardant performance with eco-friendly features.

Nonetheless, most of the research on flame-retardant chemicals remains qualitative, built upon decades of experimental knowledge. Model development to strengthen our understanding of flame retardancy remains in its early stages, especially for emerging nanocomposite materials. One of the potential approaches to studying flame-retardant mechanisms and pyrolysis chemistry is molecular dynamics simulation. This Special Issue aims to identify the most recent scientific advancements in flame-retardant materials and the characterisation of specific molecular mechanisms underlying flame retardancy. Topics of interest include: (i) bio-inspired flame retardants; (ii) multifunctional polymer composites; (iii) pyrolytic mechanisms; (iv) combustion behaviour; (v) prediction of the toxicity of gases; and (vi) molecular dynamics.

Dr. Anthony Chun Yin Yuen
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2300 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • flame retardants;
  • combustion;
  • chemical kinetics;
  • molecular dynamics;
  • material characterisation;
  • nanomaterials;
  • pyrolysis

Published Papers (7 papers)

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Research

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Article
Improved Fire Retardancy of Cellulose Fibres via Deposition of Nitrogen-Modified Biopolyphenols
Molecules 2022, 27(12), 3741; https://doi.org/10.3390/molecules27123741 - 10 Jun 2022
Viewed by 363
Abstract
Driven by concerns over the health and environmental impacts of currently used fire retardants (FRs), recent years have seen strong demand for alternative safer and sustainable bio-based FRs. In this paper, we evaluated the potential of nitrogen-modified biopolyphenols as FRs for cellulosic natural [...] Read more.
Driven by concerns over the health and environmental impacts of currently used fire retardants (FRs), recent years have seen strong demand for alternative safer and sustainable bio-based FRs. In this paper, we evaluated the potential of nitrogen-modified biopolyphenols as FRs for cellulosic natural fibres that could be used in low-density cellulose insulations. We describe the preparation and characterisation of nitrogen-modified lignin and tannin containing over 10% nitrogen as well as the treatment of cellulose pulp fibres with combinations of lignin or tannin and adsorption-enhancing retention aids. Combining lignin or tannin with a mixture of commercial bio-based flocculant (cationised tannin) and anionic retention chemical allowed for a nearly fourfold increase in lignin adsorption onto cellulosic pulp. The nitrogen-modified biopolyphenols showed significant improvement in heat release parameters in micro-scale combustion calorimetry (MCC) testing compared with their unmodified counterparts. Moreover, the adsorption of nitrogen-modified lignin or tannin onto cellulose fibres decreased the maximum heat release rate and total heat release compared with cellulose reference by 15–23%. A further positive finding was that the temperature at the peak heat release rate did not change. These results show the potential of nitrogen-modified biopolyphenols to improve fire-retarding properties of cellulosic products. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Article
An Investigation towards Coupling Molecular Dynamics with Computational Fluid Dynamics for Modelling Polymer Pyrolysis
Molecules 2022, 27(1), 292; https://doi.org/10.3390/molecules27010292 - 04 Jan 2022
Cited by 4 | Viewed by 611
Abstract
Building polymers implemented into building panels and exterior façades have been determined as the major contributor to severe fire incidents, including the 2017 Grenfell Tower fire incident. To gain a deeper understanding of the pyrolysis process of these polymer composites, this work proposes [...] Read more.
Building polymers implemented into building panels and exterior façades have been determined as the major contributor to severe fire incidents, including the 2017 Grenfell Tower fire incident. To gain a deeper understanding of the pyrolysis process of these polymer composites, this work proposes a multi-scale modelling framework comprising of applying the kinetics parameters and detailed pyrolysis gas volatiles (parent combustion fuel and key precursor species) extracted from Molecular Dynamics models to a macro-scale Computational Fluid Dynamics fire model. The modelling framework was tested for pure and flame-retardant polyethylene systems. Based on the modelling results, the chemical distribution of the fully decomposed chemical compounds was realised for the selected polymers. Subsequently, the identified gas volatiles from solid to gas phases were applied as the parent fuel in the detailed chemical kinetics combustion model for enhanced predictions of toxic gas, charring, and smoke particulate predictions. The results demonstrate the potential application of the developed model in the simulation of different polymer materials without substantial prior knowledge of the thermal degradation properties from costly experiments. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Article
Peanut Shell Derived Carbon Combined with Nano Cobalt: An Effective Flame Retardant for Epoxy Resin
Molecules 2021, 26(21), 6662; https://doi.org/10.3390/molecules26216662 - 03 Nov 2021
Viewed by 822
Abstract
Biomass-derived carbon has been recognised as a green, economic and promising flame retardant (FR) for polymer matrix. In this paper, it is considered that the two-dimensional (2D) structure of carbonised peanut shells (PS) can lead to a physical barrier effect on polymers. The [...] Read more.
Biomass-derived carbon has been recognised as a green, economic and promising flame retardant (FR) for polymer matrix. In this paper, it is considered that the two-dimensional (2D) structure of carbonised peanut shells (PS) can lead to a physical barrier effect on polymers. The carbonised sample was prepared by the three facile methods, and firstly adopted as flame retardants for epoxy resin. The results of thermal gravimetric analysis (TGA) and cone calorimeter tests indicate that the carbon combined with nano Cobalt provides the most outstanding thermal stability in the current study. With 3 wt.% addition of the FR, both peak heat release rate (pHRR) and peak smoke production rate (PSPR) decrease by 37.9% and 33.3%, correspondingly. The flame retardancy mechanisms of the FR are further explored by XPS and TG-FTIR. The effectiveness of carbonised PS can be mainly attributed to the physical barrier effect derived by PS’s 2D structure and the catalysis effect from Cobalt, which contribute to form a dense char layer. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Article
Influence of Carbon Nanotubes on Phase Composition, Thermal and Post-Heating Behavior of Cementitious Composites
Molecules 2021, 26(4), 850; https://doi.org/10.3390/molecules26040850 - 06 Feb 2021
Cited by 5 | Viewed by 719
Abstract
This paper experimentally investigates the influence of carbon nanotubes (CNTs) on phase composition, microstructure deterioration, thermal behavior, and residual mechanical strengths of cementitious composites exposed to elevated temperatures. Cement mortars with small dosages of CNTs, 0.05% and 0.2% by weight of cement, were [...] Read more.
This paper experimentally investigates the influence of carbon nanotubes (CNTs) on phase composition, microstructure deterioration, thermal behavior, and residual mechanical strengths of cementitious composites exposed to elevated temperatures. Cement mortars with small dosages of CNTs, 0.05% and 0.2% by weight of cement, were prepared and then heated at 25 °C, 150 °C, 200 °C, 450 °C, and 600 °C for two hours before being tested. The results show positive impact of the CNTs on the hydration process of cement mortar at room temperature and at higher temperatures up to 200 °C. Decomposition of the hydration products is obvious at 450 °C, whereas sever deterioration in the microstructure occurs at 600 °C. The nano reinforcement and bridging effect of the CNTs are obvious up to 450 °C. Thermal behavior characterization shows that CNTs incorporation enhances the thermal conductivity of the unheated and heat-treated mortar specimens. The decomposition of the hydration products needs more heat in the presence of CNTs. Finally, presence of CNTs significantly enhances the residual compressive and flexural strengths of heated mortar specimens for all studied temperatures. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Article
Enhanced Fire Safety of Rigid Polyurethane Foam via Synergistic Effect of Phosphorus/Nitrogen Compounds and Expandable Graphite
Molecules 2020, 25(20), 4741; https://doi.org/10.3390/molecules25204741 - 15 Oct 2020
Cited by 26 | Viewed by 1072
Abstract
In order to explore highly efficient flame-retardant rigid polyurethane foam (RPUF), phosphorus/nitrogen compounds and expandable graphite (EG) were successfully incorporated into RPUF by a free one-spot method. The combustion results showed that the fire safety of the RPUF samples was remarkably improved by [...] Read more.
In order to explore highly efficient flame-retardant rigid polyurethane foam (RPUF), phosphorus/nitrogen compounds and expandable graphite (EG) were successfully incorporated into RPUF by a free one-spot method. The combustion results showed that the fire safety of the RPUF samples was remarkably improved by the addition of phosphoric/nitrogen compounds and EG. With the incorporation of 22.4 wt.% phosphorus/nitrogen compounds and 3.2 wt.% EG, the RPUF composites achieved UL-94 V-0 rating. Besides, the total heat release and total smoke release of RPUF composites were reduced by 29.6% and 32.4% respectively, compared to those of the pure RPUF sample. PO• and PO2• together with nonflammable gaseous products were evolved from phosphoric/nitrogen compounds in the gas phase, which quenched the flammable free radicals in the matrix and diluted the concentration of combustible gaseous products generated from PRUF during combustion. The compact char residues which acted as excellent physical barriers were formed by catalysis of EG and phosphoric/nitrogen compounds in the condense phase. The fire hazard of RPUF was significantly reduced by the synergistic effect of phosphorus-nitrogen compounds and EG. This work provides a promising strategy to enhance the fire safety of RPUF. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Review

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Review
Review on the Use of Artificial Intelligence to Predict Fire Performance of Construction Materials and Their Flame Retardancy
Molecules 2021, 26(4), 1022; https://doi.org/10.3390/molecules26041022 - 15 Feb 2021
Cited by 6 | Viewed by 1620
Abstract
The evaluation and interpretation of the behavior of construction materials under fire conditions have been complicated. Over the last few years, artificial intelligence (AI) has emerged as a reliable method to tackle this engineering problem. This review summarizes existing studies that applied AI [...] Read more.
The evaluation and interpretation of the behavior of construction materials under fire conditions have been complicated. Over the last few years, artificial intelligence (AI) has emerged as a reliable method to tackle this engineering problem. This review summarizes existing studies that applied AI to predict the fire performance of different construction materials (e.g., concrete, steel, timber, and composites). The prediction of the flame retardancy of some structural components such as beams, columns, slabs, and connections by utilizing AI-based models is also discussed. The end of this review offers insights on the advantages, existing challenges, and recommendations for the development of AI techniques used to evaluate the fire performance of construction materials and their flame retardancy. This review offers a comprehensive overview to researchers in the fields of fire engineering and material science, and it encourages them to explore and consider the use of AI in future research projects. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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Review
A Review on Lithium-Ion Battery Separators towards Enhanced Safety Performances and Modelling Approaches
Molecules 2021, 26(2), 478; https://doi.org/10.3390/molecules26020478 - 18 Jan 2021
Cited by 20 | Viewed by 2999
Abstract
In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery systems has always been a global concern for the end-users. The separator is an indispensable [...] Read more.
In recent years, the applications of lithium-ion batteries have emerged promptly owing to its widespread use in portable electronics and electric vehicles. Nevertheless, the safety of the battery systems has always been a global concern for the end-users. The separator is an indispensable part of lithium-ion batteries since it functions as a physical barrier for the electrode as well as an electrolyte reservoir for ionic transport. The properties of separators have direct influences on the performance of lithium-ion batteries, therefore the separators play an important role in the battery safety issue. With the rapid developments of applied materials, there have been extensive efforts to utilize these new materials as battery separators with enhanced electrical, fire, and explosion prevention performances. In this review, we aim to deliver an overview of recent advancements in numerical models on battery separators. Moreover, we summarize the physical properties of separators and benchmark selective key performance indicators. A broad picture of recent simulation studies on separators is given and a brief outlook for the future directions is also proposed. Full article
(This article belongs to the Special Issue New Prospects in Flame-Retardant Materials)
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