Flame Retardancy Of Polymeric Materials Research Articles

“One for two” strategy to construct an organic-inorganic polymer colloid for flame-retardant modification of flax fabric and rigid polyurethane foam

Polymeric materials such as fabric and foam have high flammability which limits their application in the field of fire protection. To this end, an organic-inorganic polymer colloid constructed from carboxymethyl chitosan and ammonium polyphosphate was used to improve the flame retardancy of flax fabric (FF) and rigid polyurethane foam (RPUF) based on a “one for two” strategy. The modification processes of FF and RPUF relied on pad-dry-cure method and UV-curing technology, respectively, and the modified FF and RPUF were severally designated as CMC/APP-FF and RFR-RPUF. Flame retardancy studies showed that CMC/APP-FF and RFR-RPUF exhibited limiting oxygen index values as high as 39.4 % and 42.6 %, respectively, and both achieved self-extinguishing behavior when external ignition source was removed. Thermogravimetric analysis and cone calorimetry test confirmed that CMC/APP-FF and RFR-RPUF had good charring ability and demonstrated reduced peak heat release rate values of 90.1 % and 10.8 %, respectively, distinct from before they were modified. In addition, condensed phase analysis showed that after burning, CMC/APP-FF became an integration char structure, whereas RFR-RPUF turned into a sandwiched char structure. In summary, the “one for two” strategy reported in this work provides a new insight into the economical fabrication of flame-retardant polymeric materials.

Multiple synergistic effects of silicon-containing flame retardants and DOPO derivative enhance the flame retardancy of epoxy resin

ABSTRACT Presuming that the filler structure can regulate the flame retardancy of polymeric materials, this study investigates the flame-retardant properties of EP-containing phosphorus/silicon. Sepiolite (Sep) fibers and SiO2 nanoparticles are shown to synergistically enhance the flame retardancy of EP-based composites. The underlying retardant mechanisms of the synergistic effect are also discussed and the mechanical properties of EP-based composites are examined. Among the prepared composites, EP/DiDOPO/Sep5&SiO25 (DiDOPO = derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) achieved the maximum limiting oxygen index (29.4%) and a UL-94 V-0 rating. The EP/DiDOPO/Sep5&SiO25 composites also minimized the peak heat-release rate and total heat release and maximized the strength and modulus.

Development of a UiO-66 Based Waterborne Flame-Retardant Coating for PC/ABS Material.

The flame-retardancy of polymeric materials has garnered great interest. Most of the flame retardants used in copolymers are functionalized additives, which can deteriorate the intrinsic properties of these materials. As a new type of flame retardant, functionalized metal-organic frameworks (MOFs) can be used in surface coatings of polymers. To reduce the flammability, a mixture of phytic acid, multi-wall carbon nanotubes, zirconium-based MOFs, and UiO-66 was coated on a PC/ABS substrate. The structure of the UiO-66-based flame retardant was established by FT-IR, XRD, XPS, and SEM. The flammable properties of coated PC/ABS materials were assessed by LOI, a vertical combustion test, TGA, CCT, and Raman spectroscopy. The presence of a UiO-66-based coating on the PC/ABS surface resulted in a good flame-retardant performance. Heat release and smoke generation were significantly reduced. Importantly, the structure and mechanical properties of PC/ABS were less impacted by the presence of the flame-retardant coating. Hence, this work presents a new strategy for the development of high-performance PC/ABC materials with both excellent flame-retardancy and good mechanical properties.

Flame retardants of the future: biobased, organophosphorus, reactive or oligomeric.

Polymeric materials have been a great boon to the development and wellbeing of mankind. However, in the main, these materials are flammable and must be flame retarded for most applications. Many substances have been utilized to impart a measure of flame retardancy. The most widely used and most effective have been organic: organohalogen and organophosphorus compounds. Organohalogen compounds have been popular, low-cost, very effective flame retardants for polymeric materials. However, with the recognition that these compounds readily migrate from a polymer matrix into which they have been incorporated, persist in the environment and pose serious risks to human health, the use of organophosphorus compounds has become prominent. In particular, organophosphorus compounds of appropriate structure derived from readily-available, renewable, low-cost, non-toxic biobased precursors are attractive. Avoidance of the issues of environmental persistence and toxicity associated with organohalogen compounds is possible with these materials. Migration from a polymer matrix may be removed as a deficiency through the use of reactive compounds, i.e., compounds that may be incorporated directly into the polymer structure either by copolymerization or grafting, or oligomeric compounds. Oligomeric materials of branched structure display characteristics of broad compatibility, high effectiveness and lack of migration.

Coordination bond cleavage of metal–organic frameworks and application to flame-retardant polymeric materials

The preparation of MOF-based flame retardants derived from coordination bond cleavage is comprehensively reviewed for the first time. Furthermore, the unique advantages and future prospects of cleaved MOFs in the flame retardant field are proposed.

Metal-organic frameworks as promising flame retardants for polymeric materials

This article presents a vision for advancing the development of next-generation flame-retardant materials through the utilization of metal-organic frameworks (MOFs). The proposed vision is centered on four key areas: industrialization, multifunctionality, ligand synthesis, and derivatives. By optimizing production processes, customizing MOFs for specific properties and applications, and developing novel ligands and derivatives, the effectiveness and versatility of MOFs as flame-retardant materials can be significantly enhanced. This vision represents a promising direction for the field that has the potential to address critical safety concerns across various industries.

Bio-benzoxazine structural design strategy toward highly thermally stable and intrinsically flame-retardant thermosets

The frequent fire accidents and sustainable development concerns have called for more durable and safer flame retardant polymeric materials produced from natural renewable resources. Herein, we successfully developed a molecular design strategy by incorporating oxazine ring substituents into bio-benzoxazine monomers to achieve highly thermally stable and intrinsically flame retardant thermosets. The polybenzoxazine derived from a small-molecule bio-benzoxazine resin, 3-(furan-2-ylmethyl)-3,4-dihydro-2H-benzo[e][1,3]oxazine (PH-fa), was found to reveal a very high glass transition temperature of 317 °C. However, it was thermally unstable during the polymerization process and easy to ignite without self-extinguishing characteristic. 9,10-Dihydro-9-oxa-10-phosphaphenathrene-10-oxide (DOPO) was incorporated into PH-fa to obtain an oxazine ring substituted bio-benzoxazine (PH-fa-[4]DOPO) possessing non-ignitable capability, which reached the V-0 rating of UL-94 test. Unfortunately, a trade-off between the thermal stability and flame retardancy was discovered through the DOPO modification. Further incorporating renewable benzaldehyde into PH-fa-[4]DOPO generated a 2,4-substituted bio-benzoxazine (PH-fa-[2]ph[4]DOPO) with ideally enhanced flame retardancy as well as remained higher thermal stability. These results highlight the utility of sustainable molecular design and provide molecular-level insights into roles of oxazine ring substituents in thermal and fire-related properties of polybenzoxazines, as well as a new angle for the design of non-ignitable and high-performance bio-thermosets based on benzoxazine chemistry.

Thermal Degradation of Organophosphorus Flame Retardants.

The development of new organophosphorus flame retardants for polymeric materials is spurred by relatively low toxicity, effectiveness, and demand for replacement of more traditional materials. To function, these compounds must decompose in a degrading polymer matrix to form species which promote modification of the solid phase or generate active radical moieties that escape to the gas phase and interrupt combustion propagating reactions. An understanding of the decomposition process for these compounds may provide insight into the nature of flame retardant action which they may offer and suggest parameters for the synthesis of effective new organophosphorus flame retardants. The thermal degradation of a series of organophosphorus esters varying in the level of oxygenation at phosphorus-alkyl phosphate, aryl phosphate, phosphonate, phosphinate-has been examined. Initial degradation in all cases corresponds to elimination of a phosphorus acid. However, the facility with which this occurs is strongly dependent on the level of oxygenation at phosphorus. For alkyl phosphates elimination occurs rapidly at relatively low temperature. The same process occurs at somewhat higher temperature for aryl phosphates. Elimination of a phosphorus acid from phosphonate or phosphinate occurs more slowly and at much higher temperature. Further, the acids formed from elimination rapidly degrade further to evolve volatile species.

Synergistic flame retardant effect of carbon nanohorns and ammonium polyphosphate as a novel flame retardant system for cotton fabrics

The development of environmentally friendly flame retardants that can achieve high efficiency for textiles at low addition levels is of great significance to human life and environmental protection. Halogen flame retardants have long dominated in flame retardant applications. However, there are increasing calls to ban its use because of the threat they pose to human health and the environment. Herein, this work investigated the potential of a novel carbonaceous nanomaterials-single-walled carbon nanohorns (SWCNHs) coating material for flame retardancy of cotton fabrics. The unique combination of SWCNHs and ammonium polyphosphate (APP) in a single halogen-free nanocoating has a synergistic effect, which endows cotton fabric with prominent fire resistance. When the addition amount of SWCNHs was 0.15 %, the limit oxygen index (LOI) could reach 27.5 ± 0.83 %, and the damage length decreased from 30 ± 0.01 % cm to 6.5 ± 0.06 % cm. SEM results showed that Cotton-APP/SWCNHs (0.15) still displayed well-preserved woven structure after the vertical flammability test. Additionally, the pHRR and THR of Cotton-APP/SWCNHs (0.15) were markedly decreased by 92.22 % and 58.44 %, respectively in the cone calorimeter test. Meanwhile, the flame retardant mechanism analysis confirmed that the incorporation of SWCNHs into the APP coatings promoted the formation of dense and stable graphitized carbon layer on the surface of the cotton fabric, and effectively prevented the generation of combustible volatiles, thus enhancing the flame retardant performance of cotton fabrics. This work provides a new insight into developing carbon nanomaterials for flame retardant polymeric materials and extending the application of SWCNHs.

Precise Control of a Yolk-Double Shell Metal-Organic Framework-Based Nanostructure Provides Enhanced Fire Safety for Epoxy Nanocomposites.

Nanomaterials derived from metal-organic frameworks (MOFs) are highly promising as future flame retardants for polymeric materials. The precise control of the interface for polymer nanocomposites is taking scientific research by storm, whereas such investigations for MOF-based nanofillers are rare. Herein, a novel yolk-double shell nanostructure (ZIF-67@layered double hydroxides@polyphophazenes, ZIF@LDH@PZS) was subtly designed and introduced into epoxy resin (EP) as a flame retardant to fill the vacancy of yolk/shell construction in the field. Meanwhile, the interface of the polymer nanocomposites can be further accurately tailored by the outermost layer of the nanofillers from PZS to Ni(OH)2 (NH), by which hollow nanocages with treble shells (LDH@PZS@NH) were obtained. It is remarkably interesting that LDH@PZS@NH endows the EP with the lowest peak of heat release rate in the cone calorimeter test, but the total heat and smoke releases (THR and TSP) of the nanocomposites are even higher than those of the neat polymer. In contrast, EP blended with ZIF@LDH@PZS shows outstanding comprehensive performance: with 2 wt.%, the limiting oxygen index is increased to 29.5%, and the peak heat release rate is reduced by 26.0%. The impact and flexural strengths are slightly lowered, while the storage modulus is enhanced remarkably compared with that for neat EP. The flame retardant mechanism is systematically explored focusing on the interfacial interactions of different hybrids within the epoxy matrix, ushering in a new stage of study of nanostructural design-guided interface manipulation in MOF-based polymer nanocomposites.

A smart DOPO‐containing decoration armed on Salen‐polyphosphazene toward high‐efficient flame retardancy for epoxy thermoset

AbstractUse of Salen‐phosphazene (Salen‐PZN) complex for flame retardant polymeric materials demonstrate good flame retardancy due to their abundant flame retardant elements and aromatic‐rich structure. To further enhance their flame retardancy and interaction with the matrix, phosphorous (DK) was armed on nickel‐based Salen‐polyphosphazene complex (DK@Salen‐PZN‐Ni) as a smart decoration. The composite with DK decoration has higher tensile strength than the DK‐free composite. Moreover, cone calorimeter study showed that with 3 wt% total additive loading, the peak heat release rate (pHRR) and peak smoke rate (pSPR) of DK@Salen‐PZN‐Ni/EP composite were reduced by 21.0% and 30.3%, respectively when compared with pure EP. The limited oxygen index of the composite was 30.2%, while the vertical burning test (UL‐94) reached the V‐1 rate. Flame retardance mechanism of DK@Salen‐PZN‐Ni was discussed in detail. The designing of flame retardants alleviated the mechanical property failure and improved the flame retardancy of polymeric composite.

Nanocarbon-Based Flame Retardant Polymer Nanocomposites.

In recent years, nanocarbon materials have attracted the interest of researchers due to their excellent properties. Nanocarbon-based flame retardant polymer composites have enhanced thermal stability and mechanical properties compared with traditional flame retardant composites. In this article, the unique structural features of nanocarbon-based materials and their use in flame retardant polymeric materials are initially introduced. Afterwards, the flame retardant mechanism of nanocarbon materials is described. The main discussions include material components such as graphene, carbon nanotubes, fullerene (in preparing resins), elastomers, plastics, foams, fabrics, and film–matrix materials. Furthermore, the flame retardant properties of carbon nanomaterials and their modified products are summarized. Carbon nanomaterials not only play the role of a flame retardant in composites, but also play an important role in many aspects such as mechanical reinforcement. Finally, the opportunities and challenges for future development of carbon nanomaterials in flame-retardant polymeric materials are briefly discussed.

Solid Wastes Toward Flame Retardants for Polymeric Materials: A Review

It has been significant yet challenging to recycle and reuse different kinds of wastes because of their mass production within society. Many efforts have been conducted to reuse wastes in different fields. Interestingly, some wastes have been employed to replace traditional petroleum-based flame retardants for polymeric materials. This review focuses on the recent development of waste flame retardants and their impacts on thermal stability, flame retardancy, and smoke suppression of polymers, followed by representative flame-retardant mechanisms. Finally, the key challenges associated with waste flame retardants are presented, and some future perspectives are proposed.

Dendrimeric Epoxy Resins Based on Hexachlorocyclotriphosphazene as a Reactive Flame Retardant Polymeric Materials: A Review

In the present review article current developments on hexachlorocyclotriphosphazene (HCCP) based epoxy resins as reactive flame retardants is surveyed. The cyclotriphosphazene in its monomeric and polymeric forms behave as flame retardants due to the presence of phosphorus (P) and nitrogen (N) atoms. Usually hexachorocyclotriphosphazene based epoxy resins show reasonably low thermal and fire retardant properties therefore some external additives are being added to improved their thermal and fire retardant properties. Present review article describes the collection of previous works published on the flame retardant properties of hexachlorocyclotriphosphazene based epoxy resins. Present article also deals with the surface modification, functionalization and description of various hexachlorocyclotriphosphazene based epoxy resins as thermal and flame retardants.

Eco-friendly synergistic cross-linking flame-retardant strategy with smoke and melt-dripping suppression for condensation polymers

Conventional methods to improve the flame retardancy of polymeric materials usually involve the use of flame-retardant elements such as Cl, Br and P, however, their use may bring more smoke and toxic gases hazards, and more importantly, cause non-negligible environmental and ecological problems. In this work, we put forward a novel green strategy that eliminates the use of any conventional flame-retardant elements to improve the flame retardancy by incorporating a synergistically cross-linkable structure (named PN) containing phenylacetylene and phenylimide groups. The resulting PN copolymer exhibited an excellent 55% lower smoke release rate and 68% lower heat release rate than the pure polymer, as well as a high LOI value of 32% and UL-94 V-0 rating with excellent anti-dripping performance. TG-DSC, rheological and FTIR results proved the high cross-linking ability of the PN copolymer due to the synergistic cross-linking effect between the “imide-isoimide” rearrangement of phenylimide and the “self-cross-linking” of phenylacetylene. The SEM, Raman and Py-GC/MS results further upheld the condensed phase flame-retardant mechanism. This eco-friendly synergistic cross-linking strategy provided new perspective for the design and synthesis of polymeric materials with excellent flame retardancy, great anti-dripping performance, and low release of heat, smoke, and toxic gas.

Flame Retardancy of Biobased Composites-Research Development.

Due to the thermal and fire sensitivity of polymer bio-composite materials, especially in the case of plant-based fillers applied for them, next to intensive research on the better mechanical performance of composites, it is extremely important to improve their reaction to fire. This is necessary due to the current widespread practical use of bio-based composites. The first part of this work relates to an overview of the most commonly used techniques and different approaches towards the increasing the fire resistance of petrochemical-based polymeric materials. The next few sections present commonly used methods of reducing the flammability of polymers and characterize the most frequently used compounds. It is highlighted that despite adverse health effects in animals and humans, some of mentioned fire retardants (such as halogenated organic derivatives e.g., hexabromocyclododecane, polybrominated diphenyl ether) are unfortunately also still in use, even for bio-composite materials. The most recent studies related to the development of the flame retardation of polymeric materials are then summarized. Particular attention is paid to the issue of flame retardation of bio-based polymer composites and the specifics of reducing the flammability of these materials. Strategies for retarding composites are discussed on examples of particular bio-polymers (such as: polylactide, polyhydroxyalkanoates or polyamide-11), as well as polymers obtained on the basis of natural raw materials (e.g., bio-based polyurethanes or bio-based epoxies). The advantages and disadvantages of these strategies, as well as the flame retardants used in them, are highlighted.

Synthesis of a Novel Spirocyclic Inflatable Flame Retardant and Its Application in Epoxy Composites.

Derivatives of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]undecane-3,9-dioxide (SPDPC) are of increasing interest as flame retardants for polymeric materials. In addition, SPDPC is also an important intermediate for the preparation of intumescent flame retardants (IFRs). However, low efficiency and undesirable dispersion are two major problems that seriously restrain the application of IFRs as appropriate flame retardants for polymer materials. Usually, the functionalization or modification of SPDPC is crucial to acquiring high-performance polymer composites. Here, a small molecule spirocyclic flame retardant diphenylimidazole spirocyclic pentaerythritol bisphosphonate (PIPC) was successfully prepared through the substitution reaction between previously synthesized intermediate SPDPC and 2-phenylimidazole (PIM). Phenyl group and imidazole group were uniformly anchored on the molecular structure of SPDPC. This kind of more uniform distribution of flame retardant groups within the epoxy matrix resulted in a synergistic flame retardant effect and enhanced the strength of char layers to the epoxy composites, when compared to the unmodified epoxy. The sample reached a limiting oxygen index (LOI) of 29.7% and passed with a V-0 rating in the UL 94 test with the incorporation of only 5 wt% of as-prepared flame retardant PIPC. Moreover, its peak of heat release rate (pHRR) and total heat release (THR) decreased by 41.15% and 21.64% in a cone calorimeter test, respectively. Furthermore, the addition of PIPC has only slightly impacted the mechanical properties of epoxy composites with a low loading.

New Production Route of Magnesium Hydroxide and Related Environmental Impact

The paper presents research on a method of obtaining magnesium hydroxide from magnesium sulphate salts and NaOH. In order to acquire the desired and controlled properties, the method of precipitating in aqueous solutions by introducing a NaOH solution into a solution of MgSO4 has been applied. To get as stable a product as possible with graining, the introduction of NaOH takes place at a constant flow rate. In order to identify the environmental impact of the developed process, a life cycle assessment (LCA) has been made. The use of the proposed method for the synthesis of Mg(OH)2 incorporating washing with 25% ammonia solution and acetone enabled a product with a high specific surface area. The Mg(OH)2 obtained was characterised by a higher specific surface area than commercially available magnesium hydroxides that are used as additives for flame retardants in polymeric materials. This allows the material to be used as an anti-pyrogen for a wider group of polymeric materials. For the LCA analysis, two scenarios were assumed, from which the basic one included recovery of ammonia and acetone. The environmental analysis carried out confirmed the validity of this assumption, as it was stated that the main part of the impact was connected with the supply chain for the process examined.

Creating MXene/reduced graphene oxide hybrid towards highly fire safe thermoplastic polyurethane nanocomposites

Developing highly effective flame retardant polymeric materials with the release of low toxic fumes during burning still keep a huge challenge. In this work, we demonstrated successful synthesis of titanium carbide-reduced graphene oxide (Ti3C2Tx-rGO) hybrid via hydrogen bonding induced assembly of Ti3C2Tx and rGO, which was utilized to improve the thermal and fire safe performances of thermoplastic polyurethane elastomer (TPU). The results indicated that the Ti3C2Tx-rGO hybrid showed a strong adhesion and good compatibility with TPU host. Furthermore, as-prepared Ti3C2Tx-rGO hybrid was homogeneously dispersed in the TPU matrix due to the mutual intercalation of rGO and Ti3C2Tx preventing the re-aggregation. The thermal stability of TPU was dramatically improved after the introduction of Ti3C2Tx-rGO. With addition of 2.0 wt% Ti3C2Tx-rGO, the peak of smoke production rate and total smoke release of TPU nanocomposite were remarkably decreased by 81.2% and 54.0%, respectively. In addition, the TPU/Ti3C2Tx-rGO-2.0 showed distinct reductions in the peak of carbon monoxide production rate (54.1%) and total carbon monoxide yield (46.2%). The physical barrier effect, the catalytic charring of Ti3C2Tx-rGO hybrid and the chemical transformation of Ti3C2Tx were responsible for the excellent fire resistance of TPU/Ti3C2Tx-rGO systems. This work provides a novel strategy to significantly reduce the fire hazards of TPU, thus broadening its industrial applications.

Phosphorus esters of1‐dopyl‐1,2‐(4‐hydroxyphenyl)ethene as effective flame retardants for polymeric materials

Summary1‐Dopyl‐1,2‐(4‐hydroxyphenyl)ethene has been converted to phosphorus diesters, 1‐dopyl‐1,2‐(4‐diphenylphosphatophenyl)ethene (BDE‐DPP), and 1‐dopyl‐1,2‐(4‐dopyloxyphenyl)ethene (BDE‐DOPO) which have been fully characterized using spectroscopic and thermal methods and assessed as flame retardants in DGEBA epoxy (diglycidyl ether of bisphenol A). Both are effective flame retardants. The ester containing diphenylphosphato groups (BDE‐DPP) acts primarily in the condensed phase while that containing only dopyl units acts predominately in the gas phase. DGEBA epoxy containing sufficient 1‐dopyl‐1,2‐(4‐dopyloxyphenyl)ethene to provide 2% phosphorus displays a limiting oxygen index of 28, a peak heat release rate of 506 W/g, and a total heat release of 24 kJ/g.