Special Issue "Flame Retardancy of Polymeric Materials"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (31 December 2018).

Special Issue Editors

Prof. Paul Joseph
E-Mail Website
Guest Editor
Institute of Sustainable Industries and Liveable Cities, Victoria University, P.O. Box 14428, Melbourne, VIC 8001, Australia
Interests: polymer synthesis; environmentally sustainable flame retardant materials; cellulosic combustion and bush fires; waste recycling/management; adaptation of the existing processes/strategies towards more effective means of combustion
Special Issues and Collections in MDPI journals
Dr. Svetlana Tretsiakova-McNally
E-Mail Website
Guest Editor
Belfast School of Architecture and the Built Environment, Ulster University, Newtownabbey BT37 0QB, Northern Ireland, UK
Interests: chain-growth polymers; combustion; thermal decomposition; flammability; fire retardants; ligno-cellulosic materials; waste recycling and management; sustainability
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Every year, unwanted fires impose a huge drain on our society and economy. Furthermore, the devastations as a consequence of uncontrolled fires are growing due to the increased frequency of natural and man-made disasters and heightened degrees of threats by different terrorist groups, around the world in recent times. In addition, the problems arising from forest/bush fires, their environmental impacts including the detrimental effects on the flora and fauna and on the livelihood of the vicinal urban populations, are also on the rise.

In most of the unwanted fires, some sort of a polymeric material is usually implicated, either as a  primary source, or as a means of spreading and increasing the severity of the fires. What is even more worrying is the amount of toxic compounds  formed during the burning of polymers; a real concern given that the majority of fire fatalities are caused by the inhalation of carbon monoxide and other toxic substances from different fire loads in the enclosures. In spite of the inherent flammability attributes of, and fire hazards associated with, synthetic polymers,  their uses and demands  are on the increase. This is primarily due to their ease of production and low cost, light weight, good processability, enhanced weatherability, etc., as opposed to the conventional natural counterparts. One of the main reasons behind the successful use of polymeric-based materials in every-day-life is that, over the past decades, effective means and methods of adequately fire proofing these materials have been also brought in place.

This Special Issue, “Flame Retardancy of Polymeric Materials”, predominantly focusses on recent developments in the area of fire retardation of polymeric materials and the main topics include, but are not limited to, the following:

  1. Novel fire retarded polymeric materials
  2. Additive/reactive strategies to achieve fire retardancy
  3. Fundamentals of polymer combustion and toxicity of combustion products
  4. Polymeric hybrid materials and nanocomposites
  5. Ignition propensity, melt-flow behaviours and fire dynamics of fire retarded polymers
  6. Elements of mechanisms of fire retardant action
  7. Elucidation of condensed- and gaseous-phase chemistries
  8. Environmentally-friendly technologies and bio-inspired fire retardants
  9. Analytcal correlations of test data at different scales
  10. Mathematical modelling and software simulation of fire behaviour of polymeric materials

Whilst original contributions are normally expected, relevant reviews on topical issues in the general area of “Flame Retardancy of Polymeric Materials” are also welcome.

Prof. Paul Joseph
Dr. Svetlana Tretsiakova-McNally
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

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. Polymers is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 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

  • Novel fire retardant formulations
  • Fire retardant coatings, fibres and composites
  • Thermal degradation/decomposition and combustion of polymers
  • Calorimetric evaluations
  • Structural and morphological features of materials
  • Mechanisms of flame retardation
  • Characterisation techniques
  • Correlations of empirical parameters
  • Mathematical modelling and computational simulations

Published Papers (16 papers)

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Open AccessCommunication
Flame Retardancy Index for Thermoplastic Composites
Polymers 2019, 11(3), 407; https://doi.org/10.3390/polym11030407 - 01 Mar 2019
Cited by 6
Abstract
Flame Retardancy Index, FRI, was defined as a simple yet universal dimensionless criterion born out of cone calorimetry data on thermoplastic composites and then put into practice for quantifying the flame retardancy performance of different polymer composites on a set of reliable [...] Read more.
Flame Retardancy Index, FRI, was defined as a simple yet universal dimensionless criterion born out of cone calorimetry data on thermoplastic composites and then put into practice for quantifying the flame retardancy performance of different polymer composites on a set of reliable data. Four types of thermoplastic composites filled with a wide variety of flame retardant additives were chosen for making comparative evaluations regardless of the type and loading level of the additive as well as the irradiance flux. The main features of cone calorimetry including peak of Heat Release Rate (pHRR), Total Heat Release (THR), and Time-To-Ignition (TTI) served to calculate a dimensionless measure that reflects an improvement in the flame retardancy of nominated thermoplastic composites with respect to the neat thermoplastic, quantitatively. A meaningful trend was observed among well-classified ranges of FRI quantities calculated for the studied dataset on thermoplastic composites by which “Poor”, “Good”, and “Excellent” flame retardancy performances were explicitly defined and exhibited on logarithmic scales of FRI axis. The proposed index remains adaptable to thermoplastic systems whatever the polymer or additive is. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Investigation of the Structure-Property Effect of Phosphorus-Containing Polysulfone on Decomposition and Flame Retardant Epoxy Resin Composites
Polymers 2019, 11(2), 380; https://doi.org/10.3390/polym11020380 - 21 Feb 2019
Abstract
The flame retardant modification of epoxy (EP) is of great signification for aerospace, automotive, marine, and energy industries. In this study, a series of EP composites containing different variations of phosphorus-containing polysulfone (with a phosphorus content of approximately 1.25 wt %) were obtained. [...] Read more.
The flame retardant modification of epoxy (EP) is of great signification for aerospace, automotive, marine, and energy industries. In this study, a series of EP composites containing different variations of phosphorus-containing polysulfone (with a phosphorus content of approximately 1.25 wt %) were obtained. The obtained EP/polysulfone composites had a high glass transition temperature (Tg) and high flame retardancy. The influence of phosphorus-containing compounds (ArPN2, ArPO2, ArOPN2 and ArOPO2) on the thermal properties and flame retardancy of EP/polysulfone composites was investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), a UL-94 vertical burning test, and cone calorimeter tests. The phosphorus-containing polysulfone enhanced the thermal stability of EP. The more stable porous char layer, less flammable gases, and a lower apparent activation energy at a high degree of conversion demonstrated the high gas inhibition effect of phosphorus-containing compounds. Moreover, the gas inhibition effect of polysulfone with a P–C bond was more efficient than the polysulfone with a P–O–C bond. The potential for optimizing flame retardancy while maintaining a high Tg is highlighted in this study. The flame-retardant EP/polysulfone composites with high thermal stability broaden the application field of epoxy. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Phosphorus Containing Polyacrylamides as Flame Retardants for Epoxy-Based Composites in Aviation
Polymers 2019, 11(2), 284; https://doi.org/10.3390/polym11020284 - 08 Feb 2019
Cited by 2
Abstract
Novel polymeric flame retardants based on two acrylamides and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or 5,5-dimethyl-[1,3,2]dioxaphosphinane-2-oxide (DDPO) are described for several applications in HexFlow® RTM6, a high-performance epoxy resin. Neat resin samples and carbon fiber-reinforced composites were tested for their glass transition temperatures (dynamic mechanical [...] Read more.
Novel polymeric flame retardants based on two acrylamides and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or 5,5-dimethyl-[1,3,2]dioxaphosphinane-2-oxide (DDPO) are described for several applications in HexFlow® RTM6, a high-performance epoxy resin. Neat resin samples and carbon fiber-reinforced composites were tested for their glass transition temperatures (dynamic mechanical analysis), thermal stability (thermogravimetric analyses), flammability (UL94) and flame-retardant performance (Cone Calorimetry). Additionally, the fiber degradation occurring during combustion of carbon fiber-reinforced epoxy resins was observed by scanning electron microscopy to show the fiber protecting effect of these flame retardants. Whereas DOPO-containing polyacrylamides acting mainly in the gas phase showed the best flame retardant efficiency, DDPO-containing polyacrylamides acting mainly in the condensed phase showed the best fiber protection. A mixed polyacrylamide was synthesized to combine these effects. This thermoplastic is soluble in the resin and, therefore, suitable for injection molding processes. Interlaminar shear strength measurements showed no negative effect of the flame retardant. The versatility of these flame retardants is shown by investigations dealing with boehmite as synergist in neat resin samples. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Novel Oligo-Ester-Ether-Diol Prepared by Waste Poly(ethylene terephthalate) Glycolysis and Its Use in Preparing Thermally Stable and Flame Retardant Polyurethane Foam
Polymers 2019, 11(2), 236; https://doi.org/10.3390/polym11020236 - 01 Feb 2019
Cited by 2
Abstract
Rigid polyurethane foam (PUF) was successfully prepared from a novel oligo-ester-ether-diol obtained from the glycolysis of waste poly(ethylene terephthalate) (PET) bottles via reaction with diethylene glycol (DEG) in the presence of ZnSO4·7H2O. The LC-MS analysis of the oligodiol enabled [...] Read more.
Rigid polyurethane foam (PUF) was successfully prepared from a novel oligo-ester-ether-diol obtained from the glycolysis of waste poly(ethylene terephthalate) (PET) bottles via reaction with diethylene glycol (DEG) in the presence of ZnSO4·7H2O. The LC-MS analysis of the oligodiol enabled us to identify 67 chemical homologous structures that were composed of zero to four terephthalate (T) ester units and two to twelve monoethylene glycol (M) ether units. The flame retardant, morphological, compression, and thermal properties of rigid PUFs with and without triphenyl phosphate (TPP) were determined. The Tg values showed that TPP played a role of not only being a flame retardant, but also a plasticizer. PUF with a rather low TPP loading had an excellent flame retardancy and high thermal stability. A loading of 10 wt % TPP not only achieved a UL-94 V-0 rating, but also obtained an LOI value of 21%. Meanwhile, the PUF without a flame retardant did not achieve a UL-94 HB rating; the sample completely burned to the holder clamp and yielded a low LOI value (17%). The fire properties measured with the cone calorimeter were also discussed, and the results further proved that the flame retardancy of the PUF with the addition of TPP was improved significantly. The polymeric material meets the demands of density and compression strength for commercial PUF, as well as the needs of environmental development. The current study may help overcome the drawback of intrinsic high flammability and enlarge the fire safety applications of materials with a high percentage of recycled PET. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Electrostatic-Interaction-Driven Assembly of Binary Hybrids towards Fire-Safe Epoxy Resin Nanocomposites
Polymers 2019, 11(2), 229; https://doi.org/10.3390/polym11020229 - 01 Feb 2019
Cited by 1
Abstract
Manganese dioxide (MnO2), as a promising green material, has recently attracted considerable attention of researchers from various fields. In this work, a facile method was introduced to prepare binary hybrids by fabricating three-dimensional (3D) zinc hydroxystannate (ZHS) cubes on two-dimensional (2D) [...] Read more.
Manganese dioxide (MnO2), as a promising green material, has recently attracted considerable attention of researchers from various fields. In this work, a facile method was introduced to prepare binary hybrids by fabricating three-dimensional (3D) zinc hydroxystannate (ZHS) cubes on two-dimensional (2D) MnO2 nanosheets towards excellent flame retardancy and toxic effluent elimination of epoxy (EP) resin. Microstructural analysis confirmed that the morphologies and structures of MnO2@ZHS binary hybrids were well characterized, implying the successful synthesis. Additionally, the morphological characterization indicated that MnO2@ZHS binary hybrids could achieve satisfactory interfacial interaction with the EP matrix and be well dispersed in nanocomposites. Cone calorimeter test suggested that MnO2@ZHS binary hybrids effectively suppressed the peak of heat release rate and total heat release of EP nanocomposites, performing better than MnO2 or ZHS alone. Condensed-phase analysis revealed that MnO2@ZHS binary hybrids could promote the char density and graphitization degree of char residues and thereby successfully retard the permeation of oxygen and flammable gases. Moreover, through the analysis of gas phase, it can be concluded that MnO2@ZHS binary hybrids could efficiently suppress the production of toxic gases during the degradation of EP nanocomposites. This work implies that the construction of 2D/3D binary hybrids with an interfacial interaction is an effective way to fabricate high-performance flame retardants for EP. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Mechanism of Heat Transfer through Porous Media of Inorganic Intumescent Coating in Cone Calorimeter Testing
Polymers 2019, 11(2), 221; https://doi.org/10.3390/polym11020221 - 29 Jan 2019
Cited by 3
Abstract
This work discusses the heat transfer process through a particular form of porous media: an inorganic-based intumescent coating in full-expansion state. Although the thermal mechanism in porous media has been vigorously studied for polymeric/ceramic/metallic foams, less information is available on its application with [...] Read more.
This work discusses the heat transfer process through a particular form of porous media: an inorganic-based intumescent coating in full-expansion state. Although the thermal mechanism in porous media has been vigorously studied for polymeric/ceramic/metallic foams, less information is available on its application with intumescent-type polymers. This examination demonstrates the procedure of (1) the optimisation of the coating’s internal multicellular structure for numerical modelling, based on topological analyses; (2) the finite element simulation for the coating-sample tested with cone calorimetry; and (3) the quantitative evaluation of the thermal insulation performance of its porous structure by adopting effective thermal conductivity. The modelling technique was verified using measurable data from the cone calorimeter tests. Consistent agreement between the numerical predictions and experimental measurements was achieved over the whole steel-substrate temperature history, based on the clarified thermal boundaries of the specimen and modelling of the combined conduction-radiation transfer. This numerical approach exhibits the impacts of porosity, pore-size, and external thermal load on the medium’s performance, as well as the individual contributions of the component heat transfer modes to the overall process. The full understanding of this thermal mechanism can contribute to the enhancement and optimisation of the thermal insulation performance of a porous-type refractory polymer. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Correlation of Montmorillonite Sheet Thickness and Flame Retardant Behavior of a Chitosan–Montmorillonite Nanosheet Membrane Assembled on Flexible Polyurethane Foam
Polymers 2019, 11(2), 213; https://doi.org/10.3390/polym11020213 - 26 Jan 2019
Cited by 3
Abstract
Polymer–clay membranes constructed via the layer-by-layer (LbL) assembly, with a nanobrick wall structure, are known to exhibit high flame retardancy. In this work, chitosan–montmorillonite nanosheet (CH–MMTNS) membranes with different thickness of MMTNS were constructed to suppress the flammability of flexible polyurethane (FPU) foam. [...] Read more.
Polymer–clay membranes constructed via the layer-by-layer (LbL) assembly, with a nanobrick wall structure, are known to exhibit high flame retardancy. In this work, chitosan–montmorillonite nanosheet (CH–MMTNS) membranes with different thickness of MMTNS were constructed to suppress the flammability of flexible polyurethane (FPU) foam. It was found that a thinner MMTNS membrane was more efficient in terms of reducing the flammability of the FPU foam. This was because such MMTNS membrane could deposit cheek by jowl and form a dense CH–MMTNS membrane on the foam surface, thus greatly limiting the translation of heat, oxygen, and volatile gases. In contrast, a thicker MMTNS constructed a fragmentary CH–MMTNS membrane on the coated foam surface, due to its greater gravity and weaker electrostatic attraction of chitosan; thus, the flame retardancy of a thick MMTNS membrane was lower. Moreover, the finding of different deposition behaviors of MMTNS membranes with different thickness may suggest improvements for the application of clay with the LbL assembly technology. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Fabrication and Application of Black Phosphorene/Graphene Composite Material as a Flame Retardant
Polymers 2019, 11(2), 193; https://doi.org/10.3390/polym11020193 - 22 Jan 2019
Cited by 2
Abstract
A simple and novel route is developed for fabricating BP-based composite materials to improve the thermo-stability, flame retardant performances, and mechanical performances of polymers. Black phosphorene (BP) has outstanding flame retardant properties, however, it causes the mechanical degradation of waterborne polyurethane (WPU). In [...] Read more.
A simple and novel route is developed for fabricating BP-based composite materials to improve the thermo-stability, flame retardant performances, and mechanical performances of polymers. Black phosphorene (BP) has outstanding flame retardant properties, however, it causes the mechanical degradation of waterborne polyurethane (WPU). In order to solve this problem, the graphene is introduced to fabricate the black phosphorene/graphene (BP/G) composite material by high-pressure nano-homogenizer machine (HNHM). The structure, thermo-stability, flame retardant properties, and mechanical performance of composites are analyzed by a series of tests. The structure characterization results show that the BP/G composite material can distribute uniformly into the WPU. The addition of BP/G significantly improves the residues of WPU in both of TG analysis (5.64%) and cone calorimeter (CC) test (12.50%), which indicate that the BP/G can effectively restrict the degradation of WPU under high temperature. The CC test indicates that BP/G/WPU has a lower peak release rate (PHRR) and total heat release (THR), which decrease by 48.18% and 38.63%, respectively, than that of the pure WPU, respectively. The mechanical analysis presents that the Young’s modulus of the BP/G/WPU has an increase of seven times more than that of the BP/WPU, which indicates that the introduce of graphene can effectively improve the mechanical properties of BP/WPU. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Valorization of Industrial Lignin as Biobased Carbon Source in Fire Retardant System for Polyamide 11 Blends
Polymers 2019, 11(1), 180; https://doi.org/10.3390/polym11010180 - 21 Jan 2019
Cited by 1
Abstract
In this study, two different types of industrial lignin (i.e., lignosulphonate lignin (LL) and kraft lignin (DL)) were exploited as charring agents with phosphorus-based flame retardants for polyamide 11 (PA11). The effect of lignins on the thermal stability and fire behavior of PA11 [...] Read more.
In this study, two different types of industrial lignin (i.e., lignosulphonate lignin (LL) and kraft lignin (DL)) were exploited as charring agents with phosphorus-based flame retardants for polyamide 11 (PA11). The effect of lignins on the thermal stability and fire behavior of PA11 combined with phosphinate additives (namely, aluminum phosphinate (AlP) and zinc phosphinate (ZnP)) has been studied by thermogravimetric analysis (TGA), UL 94 vertical flame spread, and cone calorimetry tests. Various blends of flame retarded PA11 were prepared by melt process using a twin-screw extruder. Thermogravimetric analyses showed that the LL containing ternary blends are able to provide higher thermal stability, as well as a developed char residue. The decomposition of the phosphinates led to the formation of phosphate compounds in the condensed phase, which promotes the formation of a stable char. Flammability tests showed that LL/ZnP ternary blends were able to achieve self-extinction and V-1 classification; the other formulations showed a strong melt dripping and higher burning. In addition to this, cone calorimetry results showed that the most enhanced behavior was found when 10 wt % of LL and AlP were combined, which strongly reduced PHRR (−74%) and THR (−22%), due to the interaction between LL and AlP, which not only promotes char formation but also confers the stability to char in the condensed phase. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Investigation of the Flammability and Thermal Stability of Halogen-Free Intumescent System in Biopolymer Composites Containing Biobased Carbonization Agent and Mechanism of Their Char Formation
Polymers 2019, 11(1), 48; https://doi.org/10.3390/polym11010048 - 30 Dec 2018
Cited by 9
Abstract
Starch, being a polyhydric compound with its natural charring ability, is an ideal candidate to serve as a carbonization agent in an intumescent system. This charring ability of starch, if accompanied by an acidic source, can generate an effective intumescent flame retardant (IFR) [...] Read more.
Starch, being a polyhydric compound with its natural charring ability, is an ideal candidate to serve as a carbonization agent in an intumescent system. This charring ability of starch, if accompanied by an acidic source, can generate an effective intumescent flame retardant (IFR) system, but the performance of starch-based composites in an IFR system has not been tested in detail. Here, we describe a PLA-based IFR system consisting of ammonium polyphosphate (APP) as acidic source and cornstarch as carbon source. We prepared different formulations by melt compounding followed by molding into sheets by hot pressing. The thermal behavior and surface morphology of the composites was investigated by thermogravimetric analysis and scanning electron microscopy respectively. We also conducted limiting oxygen index (LOI), UL-94, and cone calorimetry tests to characterize the flame-retardant properties. Cone calorimetry revealed a 66% reduction in the peak heat release rate of the IFR composites compared to pure PLA and indicated the development of an intumescent structure by leaving a residual mass of 43% relative to the initial mass of the sample. A mechanism of char formation has also been discussed in detail. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Fire Phenomena of Rigid Polyurethane Foams
Polymers 2018, 10(10), 1166; https://doi.org/10.3390/polym10101166 - 19 Oct 2018
Cited by 6
Abstract
Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and [...] Read more.
Rigid polyurethane foams (RPUFs) typically exhibit low thermal inertia, resulting in short ignition times and rapid flame spread. In this study, the fire phenomena of RPUFs were investigated using a multi-methodological approach to gain detailed insight into the fire behaviour of pentane- and water-blown polyurethane (PUR) as well as pentane-blown polyisocyanurate polyurethane (PIR) foams with densities ranging from 30 to 100 kg/m3. Thermophysical properties were studied using thermogravimetry (TG); flammability and fire behaviour were investigated by means of the limiting oxygen index (LOI) and a cone calorimeter. Temperature development in burning cone calorimeter specimens was monitored with thermocouples inside the foam samples and visual investigation of quenched specimens’ cross sections gave insight into the morphological changes during burning. A comprehensive investigation is presented, illuminating the processes taking place during foam combustion. Cone calorimeter tests revealed that in-depth absorption of radiation is a significant factor in estimating the time to ignition. Cross sections examined with an electron scanning microscope (SEM) revealed a pyrolysis front with an intact foam structure underneath, and temperature measurement inside burning specimens indicated that, as foam density increased, their burning behaviour shifted towards that of solid materials. The superior fire performance of PIR foams was found to be based on the cellular structure, which is retained in the residue to some extent. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Development of a Semiglobal Reaction Mechanism for the Thermal Decomposition of a Polymer Containing Reactive Flame Retardants: Application to Glass-Fiber-Reinforced Polybutylene Terephthalate Blended with Aluminum Diethyl Phosphinate and Melamine Polyphosphate
Polymers 2018, 10(10), 1137; https://doi.org/10.3390/polym10101137 - 12 Oct 2018
Cited by 4
Abstract
This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced [...] Read more.
This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced polybutylene terephthalate (PBT) with aluminum diethyl phosphinate and melamine polyphosphate were used to demonstrate this methodology. These additives represent a potent solution for imparting flame retardancy to PBT. The resulting lumped-species reaction model consisted of a set of first- and second-order (two-component) reactions that defined the rate of gaseous pyrolyzate production. The heats of reaction, heat capacities of the condensed-phase reactants and products, and heats of combustion of the gaseous products were also determined. The model was shown to reproduce all aforementioned experiments with a high degree of detail. The model also captured changes in the material behavior with changes in the additive concentrations. Second-order reactions between the material constituents were found to be necessary to reproduce these changes successfully. The development of such models is an essential milestone toward the intelligent design of flame retardant materials and solid fuels. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Some Key Factors Influencing the Flame Retardancy of EDA-DOPO Containing Flexible Polyurethane Foams
Polymers 2018, 10(10), 1115; https://doi.org/10.3390/polym10101115 - 09 Oct 2018
Cited by 3
Abstract
The role of various additives (emulsifier, anti-dripping agent) and formulation procedures (pre-dispersion of solid additives in polyol via milling) which influence the flame retardancy of 6,6′-[ethan-1,2-diylbis(azandiyl)]bis(6H-dibenzo[c,e][1,2]oxaphosphin-6-oxid) (EDA-DOPO) containing flexible polyurethane foams has been investigated in this work. For comparison, the flame retardancy of [...] Read more.
The role of various additives (emulsifier, anti-dripping agent) and formulation procedures (pre-dispersion of solid additives in polyol via milling) which influence the flame retardancy of 6,6′-[ethan-1,2-diylbis(azandiyl)]bis(6H-dibenzo[c,e][1,2]oxaphosphin-6-oxid) (EDA-DOPO) containing flexible polyurethane foams has been investigated in this work. For comparison, the flame retardancy of two additional structurally-analogous bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based compounds, i.e., ethanolamine-DOPO (ETA-DOPO) and ethylene glycol-DOPO (EG-DOPO) were also evaluated together with EDA-DOPO in flexible PU foams of various formulations. The flame retardancy of these three bridged-DOPO compounds depends on the type of PU formulation. For certain PU formulations containing EDA-DOPO, lower fire performance was observed. Addition of emulsifier and polytetrafluoroethylene (PTFE) to these PU formulations influenced positively the flame retardancy of EDA-DOPO/PU foams. In addition, dispersion of EDA-DOPO and PTFE via milling in polyol improved the flame retardancy of the PU foams. Mechanistic studies performed using a microscale combustion calorimeter (MCC) and its coupling to FTIR showed no difference in the combustion efficiency of the bridged-DOPO compounds in PU foams. From MCC experiments it can be concluded that these bridged-DOPO compounds and their decomposition products may work primarily in the gas phase as flame inhibitors. The physiochemical behavior of additives in PU formulation responsible for the improvement in the flame retardancy of PU foams was further investigated by studying the dripping behavior of the PU foams in the UL 94 HB test. A high-speed camera was used to study the dripping behavior in the UL 94 HB test and results indicate a considerable reduction of the total number of melt drips and flaming drips for the flame retardant formulations. This reduction in melt drips and flaming drips during the UL 94 HB tests help PU foams achieve higher fire classification. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Flame Retardancy of Low-Viscosity Epoxy Resins and Their Carbon Fibre Reinforced Composites via a Combined Solid and Gas Phase Mechanism
Polymers 2018, 10(10), 1081; https://doi.org/10.3390/polym10101081 - 29 Sep 2018
Cited by 3
Abstract
Low viscosity, potentially renewable aliphatic epoxy resins, appropriate for processing with injection techniques were flame retarded with the use of resorcinol bis(diphenyl phosphate) (RDP), acting predominantly in the gas phase, ammonium polyphosphate (APP), acting in the solid phase, and their combination. Samples of [...] Read more.
Low viscosity, potentially renewable aliphatic epoxy resins, appropriate for processing with injection techniques were flame retarded with the use of resorcinol bis(diphenyl phosphate) (RDP), acting predominantly in the gas phase, ammonium polyphosphate (APP), acting in the solid phase, and their combination. Samples of gradually increasing phosphorus (P) content (1%, 2%, 3%, 4%, and 5%) and mixed formulations with 2% P from APP and 2% P from RDP were prepared. The fire retardancy of matrix and carbon fibre reinforced samples was examined by limiting oxygen index (LOI), UL-94 tests, and mass loss calorimetry. The thermal stability of the matrices was investigated by thermogravimetric analysis, whereas the effect of flame retardants (FRs) on the crosslinking process and glass transition temperature was evaluated by differential scanning calorimetry in matrices and by dynamic mechanical analysis in composites. According to the results, although the trifunctional glycerol -based (GER) and the tetrafunctional pentaerythritol-based (PER) epoxy resins have a similar initial LOI and horizontal burning rate, GER has an approximately 1.5 times higher peak of heat release rate (pHRR) than PER. At least 4% P content is necessary to reach a reasonable improvement in fire performance in these resin transfer molding (RTM)-compatible systems and with the same FR-content PER reaches better fire performance. RDP has an early gas phase effect at the beginning of degradation, while later on the solid phase action of APP prevails, although in composites hindered by the reinforcing carbon fibres. In PER composites, the combination of APP and RDP had a synergistic effect, leading to a pHRR of 218 kW/m2 and total heat release of 18.2 MJ/m2. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Open AccessArticle
Intumescent Polymer Metal Laminates for Fire Protection
Polymers 2018, 10(9), 995; https://doi.org/10.3390/polym10090995 - 06 Sep 2018
Cited by 3
Abstract
Intumescent paints are applied on materials to protect them against fire, but the development of novel chemistries has reached some limits. Recently, the concept of “Polymer Metal Laminates,” consisting of alternating thin aluminum foils and thin epoxy resin layers has been proven efficient [...] Read more.
Intumescent paints are applied on materials to protect them against fire, but the development of novel chemistries has reached some limits. Recently, the concept of “Polymer Metal Laminates,” consisting of alternating thin aluminum foils and thin epoxy resin layers has been proven efficient against fire, due to the delamination between layers during burning. In this paper, both concepts were considered to design “Intumescent Polymer Metal Laminates” (IPML), i.e., successive thin layers of aluminum foils and intumescent coatings. Three different intumescent coatings were selected to prepare ten-plies IPML glued onto steel substrates. The IPMLs were characterized using optical microscopy, and their efficiency towards fire was evaluated using a burn-through test. Thermal profiles obtained were compared to those obtained for a monolayer of intumescent paint. For two of three coatings, the use of IPML revealed a clear improvement at the beginning of the test, with the slopes of the curves being dramatically decreased. Characterizations (expansion measurements, microscopic analyses, in situ temperature, and thermal measurements) were carried out on the different samples. It is suggested that the polymer metal laminates (PML) design, delays the carbonization of the residue. This work highlighted that design is as important as the chemistry of the formulation, to obtain an effective fire barrier. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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Review

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Open AccessReview
Recent Advances in Bio-Based Flame Retardant Additives for Synthetic Polymeric Materials
Polymers 2019, 11(2), 224; https://doi.org/10.3390/polym11020224 - 31 Jan 2019
Cited by 6
Abstract
It would be difficult to imagine how modern life across the globe would operate in the absence of synthetic polymers. Although these materials (mostly in the form of plastics) have revolutionized our daily lives, there are consequences to their use, one of these [...] Read more.
It would be difficult to imagine how modern life across the globe would operate in the absence of synthetic polymers. Although these materials (mostly in the form of plastics) have revolutionized our daily lives, there are consequences to their use, one of these being their high levels of flammability. For this reason, research into the development of flame retardant (FR) additives for these materials is of tremendous importance. However, many of the FRs prepared are problematic due to their negative impacts on human health and the environment. Furthermore, their preparations are neither green nor sustainable since they require typical organic synthetic processes that rely on fossil fuels. Because of this, the need to develop more sustainable and non-toxic options is vital. Many research groups have turned their attention to preparing new bio-based FR additives for synthetic polymers. This review explores some of the recent examples made in this field. Full article
(This article belongs to the Special Issue Flame Retardancy of Polymeric Materials)
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