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Advanced Flame Retardant Polymeric Materials

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A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Macromolecules".

Deadline for manuscript submissions: closed (28 February 2023) | Viewed by 17541

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Special Issue Editors

Prof. Dr. Rongkun Jian

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Guest Editor

College of Chemistry and Materials Science, Fujian Normal University, Fuzhou, China
Interests: flame retardancy; polymer-based composites; flame-retardant mechanism; new fire retardants

Prof. Dr. Haibo Zhao

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Guest Editor

College of Chemistry, Sichuan University, Chengdu 610064, China
Interests: flame retardant materials; polymers; aerogels; microwave absorption materials
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Special Issue Information

Dear Colleagues,

The aim of this Special Issue, to be published in the International Journal of Molecular Sciences, is to highlight the most recent advances in and fundamentals of the preparation, performance, and applications of flame-retardant materials in view of the urgent requirement to promote the fire safety of polymeric materials.

Polymeric materials are widely used in modern society due to their low cost, light weight, ease of production, and good processability. However, they are often associated with fire hazards, posing a great impact on their use in some industries, such as transport, electronic devices, building materials, etc. Consequently, many kinds of flame retardants have been developed into polymeric materials. Nevertheless, few flame retardants are considered to be suitable for most polymeric materials. In order to meet the requirements of flame retardancy for flame retardants applied in various polymers, the development of alternative flame retardants and flame-retardant materials has attracted widespread attention.

We invite the research community to contribute to this Special Issue by submitting comprehensive reviews or original research articles. The topics of interest include, but are not limited to, the following:

New fire retardants and synergists;
Intrinsic flame-retardant polymers;
Bio-based or biomass flame retardants;
Flame-retardant coating;
Multifunctional flame retardants;
Fundamentals of polymer combustion and flame-retardant mechanisms;
Smoke, toxicity, and environmental impact.

Prof. Dr. Rongkun Jian
Prof. Dr. Haibo Zhao
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

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Keywords

flame retardants
flame retardancy
fire resistance
fire safety
bio-based flame retardants
flame-retardant coatings
hybrid materials
polymer composites
multi-functionality
fire behaviors
smoke suppression
toxicity reduction
flame-retardant mechanisms

Published Papers (10 papers)

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Research

16 pages, 5984 KiB

Open AccessArticle

Phosphorus-Containing Polybenzoxazine Aerogels with Efficient Flame Retardation and Thermal Insulation

by Yusheng Que, Chunxia Zhao, Jixuan Wei, Fahong Yang, Hui Li, Jinbo Cheng, Dong Xiang, Yuanpeng Wu and Bin Wang

Int. J. Mol. Sci. 2023, 24(5), 4314; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24054314 - 21 Feb 2023

Cited by 2 | Viewed by 1733

Abstract

Bisphenol A type benzoxazine (Ba) monomers and 10-(2, 5-dihydroxyphenyl)-10- hydrogen-9- oxygen-10- phosphine-10- oxide (DOPO-HQ) were employed to prepare flame retardant and heat insulated polybenzoxazine (PBa) composite aerogels. The successful preparation of PBa composite aerogels was confirmed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The thermal degradation behavior and flame-retardant properties of the pristine PBa and PBa composite aerogels were investigated with thermogravimetric analysis (TGA) and cone calorimeter. The initial decomposition temperature of PBa decreased slightly after incorporating DOPO-HQ, increasing the char residue amount. The incorporation of 5% DOPO-HQ into PBa led to a decrease of 33.1% at the peak of the heat-release rate and a decrease of 58.7% in the TSP. The flame-retardant mechanism of PBa composite aerogels was investigated by SEM, Raman spectroscopy, and TGA coupled with infrared spectrometry (TG-FTIR). The aerogel has advantages such as a simple synthesis procedure, easy amplification, lightweight, low thermal conductivity, and good flame retardancy. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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12 pages, 3113 KiB

Open AccessArticle

Flame-Retardant Cycloaliphatic Epoxy Systems with High Dielectric Performance for Electronic Packaging Materials

by Xiao-Wei Jia, Wen-Long Mu, Zhu-Bao Shao and Ying-Jun Xu

Int. J. Mol. Sci. 2023, 24(3), 2301; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24032301 - 24 Jan 2023

Cited by 3 | Viewed by 1824

Abstract

Flame-retardant cycloaliphatic epoxy systems have long been studied; however, the research suffers from slow and unsatisfactory advances. In this work, we synthesized a kind of phosphorus-containing difunctional cycloaliphatic epoxide (called BCEP). Then, triglycidyl isocyanurate (TGIC) was mixed with BCEP to achieve epoxy systems that are rich in phosphorus and nitrogen elements, which were cured with 4-methylhexahydrobenzene anhydride (MeHHPA) to obtain a series of flame-retardant epoxy resins. Curing behaviors, flame retardancy, thermal behaviors, dielectric performance, and the chemical degradation behaviors of the cured epoxy system were investigated. BCEP-TGIC systems showed a high curing activity, and they can be efficiently cured, in which the incorporation of TGIC decreased the curing activity of the resin. As the ratio of BCEP and TGIC was 1:3, the cured resin (BCEP₁-TGIC₃) showed a relatively good flame retardancy with a limiting oxygen index value of 25.2%. In the cone calorimeter test, they presented a longer time to ignition and a lower heat release than the commercially available cycloaliphatic epoxy resins (ERL-4221). BCEP-TGIC systems presented good thermal stability, as the addition of TGIC delayed the thermal weight loss of the resin. BCEP₁-TGIC₃ had high dielectric performance and outperformed ERL-4221 over a frequency range of 1 HZ to 1 MHz. BCEP₁-TGIC₃ could achieve degradation under mild conditions in an alkali methanol/water solution. Benefiting from the advances, BCEP-TGIC systems have potential applications as electronic packaging materials in electrical and electronic fields. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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16 pages, 4784 KiB

Open AccessArticle

High-Efficient Flame-Retardant Finishing of Cotton Fabrics Based on Phytic Acid

by Wan-Meng Song, Li-Yao Zhang, Ping Li and Yun Liu

Int. J. Mol. Sci. 2023, 24(2), 1093; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms24021093 - 6 Jan 2023

Cited by 15 | Viewed by 2619

Abstract

In this study, an efficient phosphorus-containing flame retardant, PAPBTCA, was synthesized from phytic acid, pentaerythritol, and 1,2,3,4-butane tetracarboxylic acid, and its structure was characterized. PAPBTCA was finished on cotton fabrics by the pad-dry-curing process, and the flame retardancy, flame-retardant durability, and wrinkle resistance of the obtained flame-retardant fabrics were investigated. It should be noted that the heat release rate value of the flame-retardant cotton fabrics treated with 200 g/L PAPBTCA decreased by 90% and its excellent flame retardancy was maintained after 5 washing cycles. Meanwhile, the wrinkle resistance of flame-retardant cotton fabrics has been significantly improved. In addition, compared with the control, the breaking force loss of PAPBTCA-200 in the warp and weft directions was 24% and 21%, respectively. This study provides a new way to utilize natural phosphorus-based flame retardants to establish multifunctional finishing for cotton fabrics. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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23 pages, 10654 KiB

Open AccessArticle

Preparation, Properties, and Mechanism of Flame-Retardant Poly(vinyl alcohol) Aerogels Based on the Multi-Directional Freezing Method

by Jixuan Wei, Chunxia Zhao, Zhaorun Hou, Yuntao Li, Hui Li, Dong Xiang, Yuanpeng Wu and Yusheng Que

Int. J. Mol. Sci. 2022, 23(24), 15919; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232415919 - 14 Dec 2022

Cited by 3 | Viewed by 1463

Abstract

In this work, exfoliated α-zirconium phosphate (α-ZrP) and phosphated cellulose (PCF) were employed to synthesize poly(vinyl alcohol) composite aerogels (PVA/PCF/α-ZrP) with excellent flame retardancy through the multi-directional freezing method. The peak heat release rate (PHRR), total smoke release (TSR), and CO production (COP) of the (PVA/PCF₁₀/α-ZrP₁₀-3) composite aerogel were considerably decreased by 42.3%, 41.4%, and 34.7%, as compared to the pure PVA aerogel, respectively. Simultaneously, the limiting oxygen index (LOI) value was improved from 18.1% to 28.4%. The mechanistic study of flame retardancy showed evidence that PCF and α-ZrP promoted the crosslinking and carbonization of PVA chains to form a barrier, which not only served as insulation between the material and the air, but also significantly reduced the emissions of combustible toxic gases (CO₂, CO). In addition, the multi-directional freezing method further improved the catalytic carbonization process. This mutually advantageous strategy offers a new strategy for the preparation of composite aerogels with enhanced fire resistance. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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14 pages, 4895 KiB

Open AccessArticle

Design of Hierarchically Tailored Hybrids Based on Nickle Nanocrystal-Decorated Manganese Dioxides for Enhanced Fire Safety of Epoxy Resin

by Yao Yuan, Chen Liang, Anthony Chun Yin Yuen, Lulu Xu, Bin Yu, Chengfei Cao and Wei Wang

Int. J. Mol. Sci. 2022, 23(22), 13711; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232213711 - 8 Nov 2022

Cited by 1 | Viewed by 1233

Abstract

A novel and hierarchical hybrid composite (MnO₂@CHS@SA@Ni) was synthesized utilizing manganese dioxide (MnO₂) nanosheets as the core structure, self-assembly chitosan (CHS), sodium alginate (SA) and nickel species (Ni) as surface layers, and it was further incorporated into an epoxy matrix for achieving fire hazard suppression via surface self-assembly technology. Herein, the resultant hybrid epoxy composite possessed an exceptional nano-barrier and synergistic charring effect to aid the formation of a compact layered structure that enhanced its fire-resistive effectiveness. As a result, the addition of only 2 wt% MnO₂@CHS@SA@Ni hybrids led to a dramatic reduction in the peak heat release rate and total heat release values (by ca. 33% and 27.8%) of the epoxy matrix. Notably, the peak smoke production rate and total smoke production values of EP/MnO₂@CHS@SA@Ni 2% were decreased by ca. 16.9 and 38.4% compared to the corresponding data of pristine EP. This was accompanied by the suppression of toxic CO, NO release and the diffusion of thermal pyrolysis gases during combustion through TG-IR results. Overall, a significant fire-testing outcome of the proposed hierarchical structure was proven to be effective for epoxy composites in terms of flammability, smoke and toxicity reductions, optimizing their prospects in other polymeric materials in the respective fields. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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15 pages, 4880 KiB

Open AccessArticle

Synergistic Function between Phosphorus-Containing Flame Retardant and Multi-Walled Carbon Nanotubes towards Fire Safe Polystyrene Composites with Enhanced Electromagnetic Interference Shielding

by Ruizhe Huang, Caiqin Gao, Yongqian Shi, Libi Fu, Yuezhan Feng and Wei Shui

Int. J. Mol. Sci. 2022, 23(21), 13434; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232113434 - 3 Nov 2022

Cited by 7 | Viewed by 1389

Abstract

As a universal polymer material, polystyrene (PS) is widely applied in electrical devices and construction. Thus, it is necessary to improve the flame retardancy and electromagnetic shielding properties of PS material. In this work, PS/silicon-wrapped ammonium polyphosphate/Inorganic acid-treated multi-walled carbon nanotubes composites (PS/SiAPP/aMWCNT, abbreviated as PAC) were prepared via methods of filtration-induced assembly and hot-pressing. Morphology and structure characterization demonstrated that SiAPP and aMWCNT had good dispersion in PS and excellent compatibility with the PS matrix. Thermogravimetric analysis revealed that the addition of aMWCNT to PS improved its thermal stability and carbon-forming characteristics. The peak heat release rate, the peak carbon monoxide production rate, and the peak smoke production rate of the PAC10 composite decreased by 53.7%, 41.9%, and 45.5%, respectively, while its electromagnetic shielding effectiveness reached 12 dB. These enhancements were attributed to the reason that SiAPP and aMWCNT synergistically catalyzed the char generation and SiAPP produced free radical scavengers and numbers of incombustible gases, which could decrease the oxygen concentration and retard the combustion reaction. Therefore, the assembled PS/SiAPP/aMWCNT system provides a new pathway to improve the flame retardant and electromagnetic shielding properties of PS. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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12 pages, 2479 KiB

Open AccessArticle

Study on the Flammability, Crystal Behaviors and Mechanical Performance of Polyamide 11 Composites by Intercalated Layered Double Hydroxides

by Cun Peng, Hua Yang and Wufei Tang

Int. J. Mol. Sci. 2022, 23(21), 12818; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms232112818 - 24 Oct 2022

Viewed by 1259

Abstract

Sulfamic acid-intercalated MgAl-LDH (SA-LDH) was prepared by an anion exchange method, and its structure was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). SA-LDH was introduced into polyamide 11 (PA11) by melt blending and to enhance the flame retardancy and mechanical properties. The scanning electron microscope (SEM) and XRD data showed that the lamellar structure of SA-LDH was partly disrupted. The cone calorimeter (CCT) results demonstrated that SA-LDH could effectively decrease the value of heat release rate, which may be ascribed to the better distribution of SA-LDH compared to LHD in the PA11 matrix. The effects of SA-LDH on the crystal behaviors of PA11 were investigated by XRD and differential scanning calorimetry (DSC), indicating that SA-LDH could induce the formation of new crystal forms and served as a heterogeneous nucleating agent. The mechanical progress caused by the incorporation of SA-LDH was correlated with compatibility improvement between SA-LDH and PA11. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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17 pages, 5821 KiB

Open AccessArticle

A Phosphorous-Based Bi-Functional Flame Retardant Based on Phosphaphenanthrene and Aluminum Hypophosphite for an Epoxy Thermoset

by Bo Xu, Yanting Liu, Simiao Wei, Siheng Zhao, Lijun Qian, Yajun Chen, Hao Shan and Qinglei Zhang

Int. J. Mol. Sci. 2022, 23(19), 11256; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms231911256 - 24 Sep 2022

Cited by 19 | Viewed by 1795

Abstract

A phosphorous-based bi-functional compound HPDAl was used as a reactive-type flame retardant (FR) in an epoxy thermoset (EP) aiming to improve the flame retardant efficiency of phosphorus-based compounds. HPDAl, consisting of two different P-groups of aluminum phosphinate (AHP) and phosphophenanthrene (DOPO) with different phosphorous chemical environments and thus exerting different FR actions, exhibited an intramolecular P-P groups synergy and possessed superior flame-retardant efficiency compared with DOPO or AHP alone or the physical combination of DOPO/AHP in EP. Adding 2 wt.% HPDAl made EP composites acquire a LOI value of 32.3%, pass a UL94 V-0 rating with a blowing-out effect, and exhibit a decrease in the heat/smoke release. The flame retardant modes of action of HPDAl were confirmed by the experiments of the scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetry–Fourier transform infrared spectroscopy–gas chromatograph/mass spectrometer (TG-FTIR-GC/MS). The results indicate that the phosphorous-based FRs show different influences on the flame retardancy of composites, mainly depending on their chemical structures. HPDAl had a flame inhibition effect in the gas phase and a charring effect in the condensed phase, with a well-balanced distribution of P content in the gas/condensed phase. Furthermore, the addition of HPDAl hardly impaired the mechanical properties of the matrix due to the link by chemical bonds between them. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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15 pages, 4535 KiB

Open AccessArticle

Comparative Study of M(Ⅱ)Al (M=Co, Ni) Layered Double Hydroxides for Silicone Foam: Characterization, Flame Retardancy, and Smoke Suppression

by Lin-Lin Zhou, Wen-Xiong Li, Hai-Bo Zhao and Bin Zhao

Int. J. Mol. Sci. 2022, 23(19), 11049; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms231911049 - 21 Sep 2022

Cited by 11 | Viewed by 1695

Abstract

To compare the different actions of the two representative transition metal cations of Co²⁺ and Ni²⁺ in layered double hydroxides (LDHs), CoAl-LDH and NiAl-LDH intercalated with CO₃²⁻ were synthesized, and the chemical structures, microstructures, and surface areas thereof were successfully characterized. Then, the two LDHs were utilized as flame retardants and smoke suppressants for silicone foam (SiF). The densities, flame retardancy, smoke suppression, thermal stabilities, and compressive strengths of the two SiF/LDHs nanocomposites were investigated. The introduction of LDHs slightly decreased the density of SiF due to the catalytic actions of Co and Ni during the foaming process of SiF. With respect to the flame retardancy, the addition of only 1 phr of either CoAl-LDH or NiAl-LDH could effectively improve the limiting oxygen index of SiF from 28.7 to 29.6%. Based on the results of vertical flame testing and a cone calorimeter test, the flame retardancy and fire safety of the SiF were effectively enhanced by the incorporation of LDHs. In addition, owing to the good catalytic action and large specific surface area (NiAl-LDH: 174.57 m² g⁻¹; CoAl-LDH: 51.47 m² g⁻¹), NiAl-LDH revealed higher efficiencies of flame retardancy and smoke suppression than those of CoAl-LDH. According to the results of energy-dispersive X-ray spectroscopy, Co and Ni participated in the formation of protective char layers, which inhibited the release of SiO₂ into the gas phase. Finally, the influences on the thermal decomposition and compressive strength for SiF resulting from the addition of LDHs are discussed. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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15 pages, 9221 KiB

Open AccessArticle

Phytic Acid-Iron/Laponite Coatings for Enhanced Flame Retardancy, Antidripping and Mechanical Properties of Flexible Polyurethane Foam

by Qi Jiang, Ping Li, Yun Liu and Ping Zhu

Int. J. Mol. Sci. 2022, 23(16), 9145; https://0-doi-org.brum.beds.ac.uk/10.3390/ijms23169145 - 15 Aug 2022

Cited by 12 | Viewed by 1547

Abstract

The use of flexible polyurethane foam (FPUF) is severely limited due to its flammability and dripping, which can easily cause major fire hazards. Therefore, choosing an appropriate flame retardant to solve this problem is an urgent need. A coating was prepared on the FPUF surface by dipping with phytic acid (PA), Fe₂(SO₄)₃·xH₂O, and laponite (LAP). The influence of PA-Fe/LAP coating on FPUF flame-retardant performance was explored by thermal stability, flame retardancy, combustion behavior, and smoke density analysis. FPUF/PA-Fe/LAP has a good performance in the small fire test, which can pass the UL-94 V-0 rating and the limiting oxygen index reaches 24.5%. Meanwhile, the peak heat release rate values and maximum smoke density of FPUF/PA-Fe/LAP are reduced by 38.7% and 38.5% compared with those of neat FPUF. After applying PA-Fe/LAP coating, the value of fire growth rate index decreases from 10.5 kW/(m²·s) to 5.1 kW/(m²·s), dramatically reducing the fire risk. Encouragingly, the effect of PA-Fe/LAP coating on cyclic compression and permanent deformation is small, which is close to that of neat FPUF. This work provides an effective strategy for making a flame-retardant FPUF with antidripping and keeping mechanical properties. Full article

(This article belongs to the Special Issue Advanced Flame Retardant Polymeric Materials)

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