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Editorial

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4 pages, 490 KiB

Open AccessEditorial

Advances in Novel Flame-Retardant Technologies for Fire-Safe Polymeric Materials

by Xin Wang, Weiyi Xing and Gang Tang

Molecules 2024, 29(3), 573; https://doi.org/10.3390/molecules29030573 - 24 Jan 2024

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Abstract

This Special Issue, titled “Advances in Novel Flame-Retardant Technologies for Fire-Safe Polymeric Materials”, aims to detail the recent advances in the design and preparation of novel flame retardants for use in fire-safe polymeric materials [...] Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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Research

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12 pages, 2783 KiB

Open AccessArticle

Enhancing Flame Retardancy and Smoke Suppression in Epoxy Resin Composites with Sulfur–Phosphorous Reactive Flame Retardant

by Xulong Ma, Ni Kang, Yonghang Zhang, Yang Min, Jianhua Yang, Daming Ban and Wei Zhao

Molecules 2024, 29(1), 227; https://doi.org/10.3390/molecules29010227 - 31 Dec 2023

Viewed by 851

Abstract

The presence of massive amounts of toxic volatiles and smoke during combustion is a very serious problem facing epoxy resin (EP) composites. Therefore, flame retardants (FRs) can simultaneously enhance flame retardancy and reduce the release of smoke and fatal gases. Herein, a novel [...] Read more.

The presence of massive amounts of toxic volatiles and smoke during combustion is a very serious problem facing epoxy resin (EP) composites. Therefore, flame retardants (FRs) can simultaneously enhance flame retardancy and reduce the release of smoke and fatal gases. Herein, a novel sulfur–phosphorous reactive flame retardant (SPMS) was synthesized for epoxy resin. The high efficiency of smoke suppression and flame retardancy of the EP/SPMS-APP hybrid was investigated using a cone calorimeter, a vertical burning test, and limited oxygen index measurements. Compared with those of pure EP, the composite with 20 wt% SPMS-APP reduced the peak heat release rate (pHRR), the peak smoke production rate (SPR), and total smoke production rate (TSR) by 82%, 94%, and 84%, respectively. The results showed a remarkable suppressed effect of alleviating the fire hazard of EP using a sulfur–phosphorus flame retardant. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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18 pages, 3531 KiB

Open AccessArticle

The Effect of Flame-Retardant Additives DDM-DOPO and Graphene on Flame Propagation over Glass-Fiber-Reinforced Epoxy Resin under the Influence of External Thermal Radiation

by Oleg P. Korobeinichev, Egor A. Sosnin, Artem A. Shaklein, Alexander I. Karpov, Albert R. Sagitov, Stanislav A. Trubachev, Andrey G. Shmakov, Alexander A. Paletsky and Ilya V. Kulikov

Molecules 2023, 28(13), 5162; https://doi.org/10.3390/molecules28135162 - 1 Jul 2023

Cited by 3 | Viewed by 1220

Abstract

The flammability of various materials used in industry is an important issue in the modern world. This work is devoted to the study of the effect of flame retardants, graphene and DDM-DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-4,4′-diamino-diphenyl methane), on the flammability of glass-fiber-reinforced epoxy resin (GFRER). Samples [...] Read more.

The flammability of various materials used in industry is an important issue in the modern world. This work is devoted to the study of the effect of flame retardants, graphene and DDM-DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-4,4′-diamino-diphenyl methane), on the flammability of glass-fiber-reinforced epoxy resin (GFRER). Samples were made without additives and with additives of fire retardants: graphene and DDM-DOPO in various proportions. To study the flammability of the samples, standard flammability tests were carried out, such as thermogravimetric analysis, the limiting oxygen index (LOI) test, and cone calorimetry. In addition, in order to test the effectiveness of fire retardants under real fire conditions, for the first time, the thermal structure of downward flame propagation over GFRER composites was measured using thin thermocouples. For the first time, the measured thermal structure of the flame was compared with the results of numerical simulations of flame propagation over GFRER. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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13 pages, 3042 KiB

Open AccessArticle

Effect of Layered Aminovanadic Oxalate Phosphate on Flame Retardancy of Epoxy Resin

by Po Hu, Weixi Li, Shuai Huang, Zongmian Zhang, Hong Liu, Wang Zhan, Mingyi Chen and Qinghong Kong

Molecules 2023, 28(8), 3322; https://doi.org/10.3390/molecules28083322 - 9 Apr 2023

Viewed by 1073

Abstract

To alleviate the fire hazard of epoxy resin (EP), layered ammonium vanadium oxalate-phosphate (AVOPh) with the structural formula of (NH₄)₂[VO(HPO₄)]₂(C₂O₄)·5H₂O is synthesized using the hydrothermal method and mixed into [...] Read more.

To alleviate the fire hazard of epoxy resin (EP), layered ammonium vanadium oxalate-phosphate (AVOPh) with the structural formula of (NH₄)₂[VO(HPO₄)]₂(C₂O₄)·5H₂O is synthesized using the hydrothermal method and mixed into an EP matrix to prepare EP/AVOPh composites. The thermogravimetric analysis (TGA) results show that AVOPh exhibits a similar thermal decomposition temperature to EP, which is suitable for flame retardancy for EP. The incorporation of AVOPh nanosheets greatly improves the thermal stability and residual yield of EP/AVOPh composites at high temperatures. The residue of pure EP is 15.3% at 700 °C. In comparison, the residue of EP/AVOPh composites is increased to 23.0% with 8 wt% AVOPh loading. Simultaneously, EP/6 wt% AVOPh composites reach UL-94 V1 rating (t₁ + t₂ =16 s) and LOI value of 32.8%. The improved flame retardancy of EP/ AVOPh composites is also proven by the cone calorimeter test (CCT). The results of CCT of EP/8 wt% AVOPh composites show that the peak heat release rate (PHHR), total smoke production (TSP), peak of CO production (PCOP), and peak of CO₂ production (PCO₂P) decrease by 32.7%, 20.4%, 37.1%, and 33.3% compared with those of EP, respectively. This can be attributed to the lamellar barrier, gas phase quenching effect of phosphorus-containing volatiles, the catalytic charring effect of transition metal vanadium, and the synergistic decomposition of oxalic acid structure and charring effect of phosphorus phase, which can insulate heat and inhibit smoke release. Based on the experimental data, AVOPh is expected to serve as a new high-efficiency flame retardant for EP. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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12 pages, 4376 KiB

Open AccessArticle

Amino Phenyl Copper Phosphate-Bridged Reactive Phosphaphenanthrene to Intensify Fire Safety of Epoxy Resins

by Huiyu Chai, Weixi Li, Shengbing Wan, Zheng Liu, Yafen Zhang, Yunlong Zhang, Junhao Zhang and Qinghong Kong

Molecules 2023, 28(2), 623; https://doi.org/10.3390/molecules28020623 - 7 Jan 2023

Cited by 6 | Viewed by 1586

Abstract

To improve the compatibility between flame retardant and epoxy resin (EP) matrix, amino phenyl copper phosphate-9, 10-dihydro-9-oxygen-10-phospha-phenanthrene-10-oxide (CuPPA-DOPO) is synthesized through surface grafting, which is blended with EP matrix to prepare EP/CuPPA-DOPO composites. The amorphous structure of CuPPA-DOPO is characterized by X-ray diffraction [...] Read more.

To improve the compatibility between flame retardant and epoxy resin (EP) matrix, amino phenyl copper phosphate-9, 10-dihydro-9-oxygen-10-phospha-phenanthrene-10-oxide (CuPPA-DOPO) is synthesized through surface grafting, which is blended with EP matrix to prepare EP/CuPPA-DOPO composites. The amorphous structure of CuPPA-DOPO is characterized by X-ray diffraction and Fourier-transform infrared spectroscopy. Scanning electron microscope (SEM) images indicate that the agglomeration of hybrids is improved, resisting the intense intermolecular attractions on account of the acting force between CuPPA and DOPO. The results of thermal analysis show that CuPPA-DOPO can promote the premature decomposition of EP and increase the residual amount of EP composites. It is worth mentioning that EP/6 wt% CuPPA-DOPO composites reach UL-94 V-1 level and limiting oxygen index (LOI) of 32.6%. Meanwhile, their peak heat release rate (PHRR), peak smoke production release (PSPR) and CO₂ production (CO₂P) are decreased by 52.5%, 26.1% and 41.4%, respectively, compared with those of EP. The inhibition effect of CuPPA-DOPO on the combustion of EP may be due to the release of phosphorus and ammonia free radicals, as well as the catalytic charring ability of metal oxides and phosphorus phases. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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14 pages, 8355 KiB

Open AccessArticle

Flame-Retarded Rigid Polyurethane Foam Composites with the Incorporation of Steel Slag/Dimelamine Pyrophosphate System: A New Strategy for Utilizing Metallurgical Solid Waste

by Mingxin Zhu, Sujie Yang, Zhiying Liu, Shunlong Pan and Xiuyu Liu

Molecules 2022, 27(24), 8892; https://doi.org/10.3390/molecules27248892 - 14 Dec 2022

Cited by 1 | Viewed by 1314

Abstract

Rigid polyurethane (RPUF) was widely used in external wall insulation materials due to its good thermal insulation performance. In this study, a series of RPUF and RPUF-R composites were prepared using steel slag (SS) and dimelamine pyrophosphate (DMPY) as flame retardants. The RPUF [...] Read more.

Rigid polyurethane (RPUF) was widely used in external wall insulation materials due to its good thermal insulation performance. In this study, a series of RPUF and RPUF-R composites were prepared using steel slag (SS) and dimelamine pyrophosphate (DMPY) as flame retardants. The RPUF composites were characterized by thermogravimetric (TG), limiting oxygen index (LOI), cone calorimetry (CCT), and thermogravimetric infrared coupling (TG-FTIR). The results showed that the LOI of the RPUF-R composites with DMPY/SS loading all reached the combustible material level (22.0 vol%~27.0 vol%) and passed UL-94 V0. RPUF-3 with DMPY/SS system loading exhibited the lowest pHRR and THR values of 134.9 kW/m² and 16.16 MJ/m², which were 54.5% and 42.7% lower than those of unmodified RPUF, respectively. Additionally, PO· and PO₂· free radicals produced by pyrolysis of DMPY could capture high energy free radicals, such as H·, O·, and OH·, produced by degradation of RPUF matrix, effectively blocking the free radical chain reaction of composite materials. The metal oxides in SS reacted with the polymetaphosphoric acid produced by the pyrolysis of DMPY in combustion. It covered the surface of the carbon layer, significantly insulating heat and mass transport in the combustion area, endowing RPUF composites with excellent fire performance. This work not only provides a novel strategy for the fabrication of high-performance RPUF composites, but also elucidates a method of utilizing metallurgical solid waste. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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12 pages, 4945 KiB

Open AccessArticle

A Bridge-Linked Phosphorus-Containing Flame Retardant for Endowing Vinyl Ester Resin with Low Fire Hazard

by Zihui Xu, Jing Zhan, Zhirong Xu, Liangchen Mao, Xiaowei Mu and Ran Tao

Molecules 2022, 27(24), 8783; https://doi.org/10.3390/molecules27248783 - 11 Dec 2022

Cited by 6 | Viewed by 1560

Abstract

The high flammability of vinyl ester resin (VE) significantly limits its widespread application in the fields of electronics and aerospace. A new phosphorus-based flame retardant 6,6’-(1-phenylethane-1,2 diyl) bis (dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (PBDOO), was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acetophenone. The synthesized PBDOO was further [...] Read more.

The high flammability of vinyl ester resin (VE) significantly limits its widespread application in the fields of electronics and aerospace. A new phosphorus-based flame retardant 6,6’-(1-phenylethane-1,2 diyl) bis (dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (PBDOO), was synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and acetophenone. The synthesized PBDOO was further incorporated with VE to form the VE/PBDOO composites, which displayed an improved flame retardancy with higher thermal stability. The structure of PBDOO was investigated using Fourier transformed infrared spectrometry (FTIR) and nuclear magnetic resonances (NMR). The thermal stability and flame retardancy of VE/PBDOO composites were investigated by thermogravimetric analysis (TGA), vertical burn test (UL-94), limiting oxygen index (LOI), and cone calorimetry. The impacts of PBDOO weight percentage (wt%) on the flame-retardant properties of the formed VE/PBDOO composites were also examined. When applying 15 wt% PBDOO, the formed VE composites can meet the UL-94 V-0 rating with a high LOI value of 31.5%. The peak heat release rate (PHRR) and the total heat release (THR) of VE loaded 15 wt% of PBDOO decreased by 76.71% and 40.63%, respectively, compared with that of untreated VE. In addition, the flame-retardant mechanism of PBDOO was proposed by analyzing pyrolysis behavior and residual carbon of VE/PBDOO composites. This work is expected to provide an efficient method to enhance the fire safety of VE. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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Review

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19 pages, 3861 KiB

Open AccessReview

Advancements in Flame-Retardant Systems for Rigid Polyurethane Foam

by Yao Yuan, Weiliang Lin, Yi Xiao, Bin Yu and Wei Wang

Molecules 2023, 28(22), 7549; https://doi.org/10.3390/molecules28227549 - 11 Nov 2023

Viewed by 2142

Abstract

The amplified employment of rigid polyurethane foam (RPUF) has accentuated the importance of its flame-retardant properties in stimulating demand. Thus, a compelling research report is essential to scrutinize the recent progression in the field of the flame retardancy and smoke toxicity reduction of [...] Read more.

The amplified employment of rigid polyurethane foam (RPUF) has accentuated the importance of its flame-retardant properties in stimulating demand. Thus, a compelling research report is essential to scrutinize the recent progression in the field of the flame retardancy and smoke toxicity reduction of RPUF. This comprehensive analysis delves into the conventional and innovative trends in flame-retardant (FR) systems, comprising reactive-type FRs, additive-type FRs, inorganic nanoparticles, and protective coatings for flame resistance, and summarizes their impacts on the thermal stability, mechanical properties, and smoke toxicity suppression of the resultant foams. Nevertheless, there are still several challenges that require attention, such as the migration of additives, the insufficient interfacial compatibility between flame-retardant polyols or flame retardants and the RPUF matrix, and the complexity of achieving both flame retardancy and mechanical properties simultaneously. Moreover, future research should focus on utilizing functionalized precursors and developing biodegradable RPUF to promote sustainability and to expand the applications of polyurethane foam. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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22 pages, 8445 KiB

Open AccessReview

Multifunctional Textiles with Flame Retardant and Antibacterial Properties: A Review

by Liping Jin, Chenpeng Ji, Shun Chen, Zhicong Song, Juntong Zhou, Kun Qian and Wenwen Guo

Molecules 2023, 28(18), 6628; https://doi.org/10.3390/molecules28186628 - 14 Sep 2023

Cited by 2 | Viewed by 1774

Abstract

It is well known that bacterial infections and fire-hazards are potentially injurious in daily life. With the increased security awareness of life and properties as well as the improvement of living standards, there has been an increasing demand for multifunctional textiles with flame [...] Read more.

It is well known that bacterial infections and fire-hazards are potentially injurious in daily life. With the increased security awareness of life and properties as well as the improvement of living standards, there has been an increasing demand for multifunctional textiles with flame retardant and antibacterial properties, especially in the fields of home furnishing and medical protection. So far, various treatment methods, including the spray method, the dip-coating method, and the pad-dry-cure method, have been used to apply functional finishing agents onto fabrics to achieve the functionalization in the past exploration stage. Moreover, in addition to the traditional finishing technology, a number of novel technologies have emerged, such as layer-by-layer (LBL) deposition, the sol-gel process, and chemical grafting modification. In addition, some natural biomasses, including chitin, chitosan (CS), and several synthetic functional compounds that possess both flame-retardant and bacteriostatic properties, have also received extensive attention. Hence, this review focuses on introducing some commonly used finishing technologies and flame retardant/antibacterial agents. At the same time, the advantages and disadvantages of different methods and materials were summarized, which will contribute to future research and promote the development and progress of the industry. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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28 pages, 24822 KiB

Open AccessReview

Synthesis and Applications of Supramolecular Flame Retardants: A Review

by Simeng Xiang, Jiao Feng, Hongyu Yang and Xiaming Feng

Molecules 2023, 28(14), 5518; https://doi.org/10.3390/molecules28145518 - 19 Jul 2023

Cited by 1 | Viewed by 1435

Abstract

The development of different efficient flame retardants (FRs) to improve the fire safety of polymers has been a hot research topic. As the concept of green sustainability has gradually been raised to the attention of the whole world, it has even dominated the [...] Read more.

The development of different efficient flame retardants (FRs) to improve the fire safety of polymers has been a hot research topic. As the concept of green sustainability has gradually been raised to the attention of the whole world, it has even dominated the research direction of all walks of life. Therefore, there is an urgent calling to explore the green and simple preparation methods of FRs. The development of supramolecular chemistry in the field of flame retardancy is expanding gradually. It is worth noting that the synthesis of supramolecular flame retardants (SFRs) based on non-covalent bonds is in line with the current concepts of environmental protection and multi-functionality. This paper introduces the types of SFRs with different dimensions. SFRs were applied to typical polymers to improve their flame retardancy. The influence on mechanical properties and other material properties under the premise of flame retardancy was also summarized. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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19 pages, 4288 KiB

Open AccessReview

Facile Ball Milling Preparation of Flame-Retardant Polymer Materials: An Overview

by Xiaming Feng, Xiang Lin, Kaiwen Deng, Hongyu Yang and Cheng Yan

Molecules 2023, 28(13), 5090; https://doi.org/10.3390/molecules28135090 - 29 Jun 2023

Cited by 2 | Viewed by 1750

Abstract

To meet the growing needs of public safety and sustainable development, it is highly desirable to develop flame-retardant polymer materials using a facile and low-cost method. Although conventional solution chemical synthesis has proven to be an efficient way of developing flame retardants, it [...] Read more.

To meet the growing needs of public safety and sustainable development, it is highly desirable to develop flame-retardant polymer materials using a facile and low-cost method. Although conventional solution chemical synthesis has proven to be an efficient way of developing flame retardants, it often requires organic solvents and a complicated separation process. In this review, we summarize the progress made in utilizing simple ball milling (an important type of mechanochemical approach) to fabricate flame retardants and flame-retardant polymer composites. To elaborate, we first present a basic introduction to ball milling, and its crushing, exfoliating, modifying, and reacting actions, as used in the development of high-performance flame retardants. Then, we report the mixing action of ball milling, as used in the preparation of flame-retardant polymer composites, especially in the formation of multifunctional segregated structures. Hopefully, this review will provide a reference for the study of developing flame-retardant polymer materials in a facile and feasible way. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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Other

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10 pages, 2861 KiB

Open AccessBrief Report

Functionally Active Microheterogeneous Systems for Elastomer Fire- and Heat-Protective Materials

by Victor F. Kablov, Oksana M. Novopoltseva, Daria A. Kryukova, Natalia A. Keibal, Vladimir Burmistrov and Vladimir G. Kochetkov

Molecules 2023, 28(13), 5267; https://doi.org/10.3390/molecules28135267 - 7 Jul 2023

Cited by 1 | Viewed by 820

Abstract

Elastomeric materials are utilized for the short-term protection of products and structures operating under extreme conditions in the aerospace, marine, and oil and gas industries. This research aims to study the influence of functionally active structures on the physical, mechanical, thermophysical, and fire- [...] Read more.

Elastomeric materials are utilized for the short-term protection of products and structures operating under extreme conditions in the aerospace, marine, and oil and gas industries. This research aims to study the influence of functionally active structures on the physical, mechanical, thermophysical, and fire- and heat-protective characteristics of elastomer compositions. The physical and mechanical properties of elastomer samples were determined using Shimazu AG-Xplus, while morphological research into microheterogeneous systems and coke structures was carried out on a scanning electronic microscope, Versa 3D. Differential thermal and thermogravimetric analyses of the samples were conducted on derivatograph Q-1500D. The presence of aluminosilicate microspheres, carbon microfibers, and a phosphor–nitrogen–organic modifier as part of the aforementioned structures contributes to the appearance of a synergetic effect, which results in an increase in the heat-protective properties of a material due to the enhancement in coke strength and intensification of material carbonization processes. The results indicate an 8–17% increase in the heating time of the unheated surface of a sample and a decrease in its linear burning speed by 6–17% compared to known analogues. In conclusion, microspheres compensate for the negative impact of microfibers on the density and thermal conductivity of a composition. Full article

(This article belongs to the Special Issue Advances in Novel Flame Retardant Technologies for Fire-Safe Polymeric Materials)

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