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Polymers
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Flame-Retardant Polymer Composites
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Flame-Retardant Polymer Composites

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: closed (25 March 2023) | Viewed by 38542

Special Issue Editors

Dr. Marcos Batistella

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Guest Editor
IMT Mines Alès, 30100 Alès, France
Interests: flame retardancy; polymers; mineral fillers; additive manufacturing; polymer composites
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Laurent Ferry

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Guest Editor
IMT Mines Ales, Centre des Matériaux des Mines d’Alès (C2MA), 6 Avenue de Clavières, CEDEX, 30319 Alès, France
Interests: flame retardancy; fire behavior; thermal degradation of polymers
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Polymer composites are widely used in various industrial applications such as transport, wind energy production, aerospace, defense, and electronics, among others. Moreover, these materials are often associated with fire hazards, which limits their use in some industries, such as transport and defense. Therefore, the flammability of composites must be evaluated and, if needed, flame retardants, nanofillers, inorganic particles, or other additives should be used in order to improve their fire behavior.

Flame-retardant polymer composites can be obtained by various processing routes, such as injection molding, thermocompression, or additive manufacturing (AM). Recently, the use of AM has increased the possibilities of the use of polymer composites because it allows the production of very complex parts. However, some composites are not suitable for AM due to the specificities of these technologies. Furthermore, some additives are prone to affect composites’ functional properties regardless of the processing route. Thus, composites and additives should be carefully selected in order to avoid problems during processing, and effective flame-retardant systems should be chosen or developed in order to meet the requirements of the new applications.

Hence, this Special Issue aims to identify the most recent scientific advancements in the flame retardancy of polymer composites processed through different routes, as well as the characterization of the flame retardancy mechanisms.

Dr. Marcos Batistella
Prof. Dr. Laurent Ferry 
Guest Editors

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 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

  • polymer composites
  • fire behavior
  • additive manufacturing
  • injection molding
  • thermocompression
  • flame retardancy
  • inorganic fillers

Published Papers (23 papers)

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Research

11 pages, 4049 KiB  
Article
Fire Performance of Cotton Fabrics Coated with 10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-xa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) Zr-Based Metal-Organic Frameworks
by Qiuyue Wu, Manuel José Lis and Juan P. Hinestroza
Polymers 2023, 15(22), 4379; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15224379 - 10 Nov 2023
Viewed by 836
Abstract
We investigated the performance of cotton fabrics coated with DOPO-HQ and Zr-based Metal–organic Frameworks when exposed to fire. The chemical structure of the cotton fabrics before and after the coating was characterized using FTIR spectroscopy, and the surface morphology of cotton and their [...] Read more.
We investigated the performance of cotton fabrics coated with DOPO-HQ and Zr-based Metal–organic Frameworks when exposed to fire. The chemical structure of the cotton fabrics before and after the coating was characterized using FTIR spectroscopy, and the surface morphology of cotton and their combustion residues was probed via scanning electron microscopy. In our experiments, we used flammability tests and thermogravimetric methods to understand the burning behavior of the coated fibers, as well as their thermal stability. The cotton fabrics coated with DOPO-HQ and Zr MOFs exhibited shorter combustion times, had better thermal degradation properties, promoted the creation of heat-insulating layers, and exhibited improved smoke suppression behavior. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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19 pages, 3085 KiB  
Article
Effects of Additives on the Mechanical and Fire Resistance Properties of Pultruded Composites
by Natalia Romanovskaia, Kirill Minchenkov, Sergey Gusev, Olga Klimova-Korsmik and Alexander Safonov
Polymers 2023, 15(17), 3581; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15173581 - 29 Aug 2023
Cited by 2 | Viewed by 1098
Abstract
Under high temperatures, fiber-reinforced polymers are destroyed, releasing heat, smoke, and harmful volatile substances. Therefore, composite structural elements must have sufficient fire resistance to meet the requirements established by building codes and regulations. Fire resistance of composite materials can be improved by using [...] Read more.
Under high temperatures, fiber-reinforced polymers are destroyed, releasing heat, smoke, and harmful volatile substances. Therefore, composite structural elements must have sufficient fire resistance to meet the requirements established by building codes and regulations. Fire resistance of composite materials can be improved by using mineral fillers as flame-retardant additives in resin compositions. This article analyzes the effect of fire-retardant additives on mechanical properties and fire behavior of pultruded composite profiles. Five resin mixtures based on vinyl ester epoxy and on brominated vinyl ester epoxy modified with alumina trihydrate and triphenyl phosphate were prepared for pultrusion of strip profiles of 150 mm × 3.5 mm. A series of tests have been conducted to determine mechanical properties (tensile, flexural, compression, and interlaminar shear) and fire behavior (ignitability, flammability, combustibility, toxicity, smoke generation, and flame spread) of composites. It was found that additives impair mechanical properties of materials, as they the take place of reinforcing fibers and reduce the volume fraction of reinforcing fibers. Profiles based on non-brominated vinyl ester epoxy have higher tensile, compressive, and flexural properties than those based on brominated vinyl ester epoxy by 7%, 30%, and 36%, respectively. Profiles based on non-brominated epoxy resin emit less smoke compared to those based on brominated epoxy resin. Brominated epoxy-based profiles have a flue gas temperature which is seven times lower compared to those based on the non-brominated epoxy. Mineral fillers retard the spread of flame over the composite material surface by as much as 4 times and reduce smoke generation by 30%. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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19 pages, 4839 KiB  
Article
Incorporation of Fly Ash in Flame-Retardant Systems of Biopolyesters
by Marcos Batistella, Jean-Claude Roux, Nour-Alhoda Masarra, Gwenn le Saout, Constantinos Xenopoulos and José-Marie Lopez-Cuesta
Polymers 2023, 15(13), 2771; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15132771 - 21 Jun 2023
Cited by 1 | Viewed by 932
Abstract
The incorporation of fly ash in polybutyl succinate (PBS) and polybutyl adipate terephtalate (PBAT) in the partial replacement of ammonium polyphosphate and/or melamine polyphosphate is evaluated in the present work. Furthermore, the influence of the surface modification of fly ash with two silanes [...] Read more.
The incorporation of fly ash in polybutyl succinate (PBS) and polybutyl adipate terephtalate (PBAT) in the partial replacement of ammonium polyphosphate and/or melamine polyphosphate is evaluated in the present work. Furthermore, the influence of the surface modification of fly ash with two silanes and titanate coupling agents was also studied. Cone calorimeter experiments, pyrolysis combustion flow calorimeters (PCFCs), and UL94V tests were used to assess the fire performance of the composites. Scanning electronic microscopy, X-microanalysis, and X-ray diffractometry analysis were carried out on cone calorimeter residues in order to access the fire-retardant mode of action. The formation of new components due to the presence of fly ash was highlighted by X-ray diffractometry, indicating the synergistic effects between the flame-retardant system and fly ash. The X-microanalysis results showed that the main fraction of initial phosphorous is present in the cone calorimeter residue, indicating that the proposed system acts in a condensed phase. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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22 pages, 6300 KiB  
Article
LDH@Boronate Polymer Core–Shell Nanoparticles: Nanostructure Design for Synergistically Enhancing the Flame Retardancy of Epoxy Resin
by Cheng Chi, Siyuan He, Chaohua Peng, Birong Zeng, Long Xia, Zhongxi Miao, Hui Xu, Shuchuan Wang, Guorong Chen and Lizong Dai
Polymers 2023, 15(9), 2198; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15092198 - 05 May 2023
Cited by 5 | Viewed by 1780
Abstract
As a promising nanofiller, layered double hydroxides (LDHs) can advance the fire safety of epoxy resin (EP), but so far, due to the problems of dispersion and low efficiency, it has still been a challenge to incorporate the flame retardancy and mechanical properties [...] Read more.
As a promising nanofiller, layered double hydroxides (LDHs) can advance the fire safety of epoxy resin (EP), but so far, due to the problems of dispersion and low efficiency, it has still been a challenge to incorporate the flame retardancy and mechanical properties of EP nanocomposites effectively under the circumstance of a low additive amount. In this work, we take LDHs as the template, via the adsorption of a catechol group and the condensation polymerization between catechol groups and phenylboric acid groups, to prepare a core–shell structured nanoparticle LDH@BP, which contains rich flame-retardant elements. EP/LDH@BP nanocomposites were prepared by introducing LDH@BP into EP. The experimental results indicate that, compared with the original LDH, LDH@BP disperses uniformly in the EP matrix, and the flame retardancy and mechanical properties of EP/LDH@BP are significantly improved. At a relatively low content (5 wt%), EP/LDH@BP reached the rating of V-0 in the UL-94 test, LOI was increased to 29.1%, and peak heat release rate (PHRR) was reduced by 35.9% in cone calorimeter tests, which effectively inhibited the release of heat and toxic smoke during the combustion process of EP. Simultaneously, the mechanical properties of EP/LDH@BP have been improved satisfactorily. The above results derive from the reasonable architectural design of organic–inorganic nano-hybrid flame retardants and provide a novel method for the construction of efficient and balanced EP nanocomposite system with LDHs. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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17 pages, 10923 KiB  
Article
Simultaneously Enhancing the Flame Retardancy, Water Resistance, and Mechanical Properties of Flame-Retardant Polypropylene via a Linear Vinyl Polysiloxane-Coated Ammonium Polyphosphate
by Qining Ke, Junchen Bai, Ge Zhang, Jiacheng Zhang and Mingshu Yang
Polymers 2023, 15(9), 2074; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15092074 - 27 Apr 2023
Cited by 4 | Viewed by 1462
Abstract
It is challenging to improve the water resistance, flame retardancy, mechanical performance, and balance of halogen-free flame-retardant polypropylene (PP) composites. For this purpose, a linear vinyl polysiloxane (PD) was synthesized and then self-crosslinked under benzoyl peroxide to prepare surface-coated ammonium polyphosphate (APP@PD). Apparently, [...] Read more.
It is challenging to improve the water resistance, flame retardancy, mechanical performance, and balance of halogen-free flame-retardant polypropylene (PP) composites. For this purpose, a linear vinyl polysiloxane (PD) was synthesized and then self-crosslinked under benzoyl peroxide to prepare surface-coated ammonium polyphosphate (APP@PD). Apparently, this linear vinyl polysiloxane self-crosslinking coating strategy was completely different from the commonly used sol-gel-coated APP with silane monomers. After coating, the water contact angles (WCA) of APP and APP@PD were 26.8° and 111.7°, respectively, showing high hydrophobicity. More importantly, PP/APP@PD/dipentaerythritol (DPER) showed a higher limiting oxygen index (LOI) and better UL-94 V-0 rate in comparison with PP/APP/DPER composites. After water immersion at 70 °C for 168 h, only PP/APP@PD/DPER kept the UL-94 V-0 rate and lowered the deterioration of the LOI, reflecting the better water-resistance property of APP@PD. Consistently, the cone calorimeter test results displayed a 26.2% and 16.7% reduction in peak heat release rate (PHRR) and total smoke production (TSP), respectively. Meanwhile, the time to peak smoke production rate (TPSPR) increased by 90.2%. The interfacial free energy (IFE) between APP@PD and PP was calculated to evaluate the interfacial interaction between PP and APP@PD. A reduction of 84.2% in the IFE between APP@PD and PP is responsible for the improvement in compatibility and the increase in flame retardancy, water resistance, and mechanical properties of the composites. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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11 pages, 2421 KiB  
Article
Synergistic Flame Retardant Effect between Ionic Liquid Functionalized Imogolite Nanotubes and Ammonium Polyphosphate in Epoxy Resin
by Taohua Zhu, Xuan Zhou, Guozheng Guo, Zhihua Chai and Ming Gao
Polymers 2023, 15(6), 1455; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15061455 - 15 Mar 2023
Cited by 3 | Viewed by 1117
Abstract
Ionic liquid functionalized imogolite nanotubes (INTs-PF6-ILs) were introduced into the epoxy resin (EP)/ammonium polyphosphate (APP) system to investigate the flame retardant performance and thermal properties using the limiting oxygen index (LOI) test, the UL-94 test, and the cone calorimeter test (CCT). [...] Read more.
Ionic liquid functionalized imogolite nanotubes (INTs-PF6-ILs) were introduced into the epoxy resin (EP)/ammonium polyphosphate (APP) system to investigate the flame retardant performance and thermal properties using the limiting oxygen index (LOI) test, the UL-94 test, and the cone calorimeter test (CCT). The results suggested that a synergistic effect exists between INTs-PF6-ILs and APP on the char formation and anti-dripping behavior of EP composites. For the EP/APP, an UL-94 V-1 rating was obtained for the loading of 4 wt% APP. However, the composites containing 3.7 wt% APP and 0.3 wt% INTs-PF6-ILs could pass the UL-94 V-0 rating without dripping behavior. In addition, compared with the EP/APP composite, the fire performance index (FPI) value and fire spread index (FSI) value of EP/APP/INTs-PF6-ILs composites were remarkably reduced by 11.4% and 21.1%, respectively. Moreover, the char formed by EP/APP composites was intumescent, but of poor quality. In contrast, the char for EP/APP/INTs-PF6-ILs was strong and compact. Therefore, it can resist the erosion due to heat and gas formation and protect the inside of the matrix. This was the main reason for the good flame retardant property of EP/APP/INTs-PF6-ILs composites. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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16 pages, 6123 KiB  
Article
Flame-Retardant and Smoke-Suppressant Flexible Polyurethane Foams Based on Phosphorus-Containing Polyester Diols and Expandable Graphite
by Hongkun Wang, Qiang Liu, Hui Li, Hao Zhang and Shouke Yan
Polymers 2023, 15(5), 1284; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15051284 - 03 Mar 2023
Cited by 6 | Viewed by 2290
Abstract
A liquid-phosphorus-containing polyester diol, PPE, was prepared via condensation polymerization using commercial reactive flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide, adipic acid, ethylene glycol, and 1,4-butanediol. PPE and/or expandable graphite (EG) were then incorporated into phosphorus-containing flame-retardant polyester-based flexible polyurethane foams (P-FPUFs). The structure and properties of [...] Read more.
A liquid-phosphorus-containing polyester diol, PPE, was prepared via condensation polymerization using commercial reactive flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide, adipic acid, ethylene glycol, and 1,4-butanediol. PPE and/or expandable graphite (EG) were then incorporated into phosphorus-containing flame-retardant polyester-based flexible polyurethane foams (P-FPUFs). The structure and properties of the resultant P-FPUFs were characterized using scanning electron microscopy tensile measurements, limiting oxygen index (LOI), vertical burning tests, cone calorimeter tests, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Unlike the FPUF prepared using regular polyester polyol (R-FPUF), PPE increased the flexibility and elongation at break of the resultant forms. More importantly, the peak heat release rate (PHRR) and total heat release (THR) of P-FPUF were reduced by 18.6% and 16.3%, respectively, via gas-phase-dominated flame-retardant mechanisms, compared with those of R-FPUF. The addition of EG further reduced the peak smoke production release (PSR) and total smoke production (TSP) of the resultant FPUFs while increasing the LOI and char formation. Interestingly, it was observed that EG noticeably improved the residual quantity of phosphorus in the char residue. When the EG loading was 15 phr, the resulting FPUF (P-FPUF/15EG) attained a high LOI value (29.2%) and exhibited good anti-dripping performance. Meanwhile, the PHRR, THR, and TSP of P-FPUF/15EG were significantly decreased by 82.7%, 40.3%, and 83.4%, respectively, compared with those of P-FPUF. This superior flame-retardant performance can be attributed to the combination of the bi-phase flame-retardant behavior of PPE and condensed-phase flame-retardant characteristics of EG. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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19 pages, 7756 KiB  
Article
Bio-Based Phosphate-Containing Polyester for Improvement of Fire Reaction in Wooden Particleboard
by Ingemar Svensson, Amaia Butron, Maddalen Puyadena, Alba González, Lourdes Irusta and Aitor Barrio
Polymers 2023, 15(5), 1093; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15051093 - 22 Feb 2023
Cited by 3 | Viewed by 1824
Abstract
A new phosphate-containing bio-polyester based on glycerol and citric acid was synthesized and evaluated as fire-retardant (FR) in wooden particleboards. Phosphorus pentoxide was used to first introduce phosphate esters in the glycerol followed by esterification with citric acid to produce the bio-polyester. The [...] Read more.
A new phosphate-containing bio-polyester based on glycerol and citric acid was synthesized and evaluated as fire-retardant (FR) in wooden particleboards. Phosphorus pentoxide was used to first introduce phosphate esters in the glycerol followed by esterification with citric acid to produce the bio-polyester. The phosphorylated products were characterized by ATR-FTIR, 1H-NMR and TGA-FTIR. After polyester curing, they were grinded and incorporated in laboratory produced particleboards. The fire reaction performance of the boards was evaluated by cone calorimeter. An increased char residue was produced depending on the phosphorus content and the THR (Total Heat Release), PHRR (Peak of Heat Release Rate) and MAHRE (Maximum Average of the Rate of Heat Emission) were considerably reduced in presence of the FRs. Highlights: Phosphate containing bio-polyester as fire retardant in wooden particle board; Fire performance is improved; Bio-polyester acts in the condensed and gas phases; Additive effectiveness similar to ammonium polyphosphate. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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15 pages, 4109 KiB  
Article
Synthesis of DOPO-Based Phosphorus-Nitrogen Containing Hyperbranched Flame Retardant and Its Effective Application for Poly(ethylene terephthalate) via Synergistic Effect
by Hossamaldin Ahmed Omer Abdalrhem, Yueyue Pan, Hongda Gu, Xiang Ao, Xiaohuan Ji, Xiaoze Jiang and Bin Sun
Polymers 2023, 15(3), 662; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15030662 - 28 Jan 2023
Cited by 3 | Viewed by 2131
Abstract
To obtain industrialized poly(ethylene terephthalate) (PET) composites with highly efficient flame retardancy, a phosphorus-nitrogen (P-N) containing hyperbranched flame retardant additive was synthesized by 9,10-dihydro-9-oxa-10-phospho-phenanthrene-butyric acid (DDP) and tris(2-hydroxyethyl) isocyanurate (THEIC) through high temperature esterification known as hyperbranched DDP-THEIC (hbDT). The chemical structure of [...] Read more.
To obtain industrialized poly(ethylene terephthalate) (PET) composites with highly efficient flame retardancy, a phosphorus-nitrogen (P-N) containing hyperbranched flame retardant additive was synthesized by 9,10-dihydro-9-oxa-10-phospho-phenanthrene-butyric acid (DDP) and tris(2-hydroxyethyl) isocyanurate (THEIC) through high temperature esterification known as hyperbranched DDP-THEIC (hbDT). The chemical structure of the synthesized hbDT was determined by FTIR, 1H NMR, 13C NMR, and GPC, etc. Subsequently, hbDT/PET composites were prepared by co-blending, and the effects of hbDT on the thermal stability, flame retardancy, combustion performance, and thermal degradation behavior of PET were explored to deeply analyze its flame retardant mechanism. The test results showed that hbDT was successfully synthesized, and that hbDT maintained thermal stability well with the required processing conditions of PET as retardant additives. The flame retardant efficiency of PET was clearly improved by the addition of hbDT via the synergistic flame-retardant effect of P and N elements. When the mass fraction of flame retardant was 5%, the LOI of the hbDT/PET composite increased to 30.2%, and the vertical combustion grade reached UL-94 V-0. Compared with pure PET, great decreased total heat release (decreased by 16.3%) and peak heat release rate (decreased by 54.9%) were exhibited. Finally, the flame retardant mechanism of hbDT/PET was supposed, and it was confirmed that retardant effect happened in both the gas phase and condensed phase. This study is expected to provide a new idea for the development of low toxic, environment-friendly and highly efficient flame retardant additive for polyesters in an industry scale. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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15 pages, 9798 KiB  
Article
Thermal Decomposition and Stability of Hybrid Graphene–Clay/Polyimide Nanocomposites
by Caroline Akinyi and Jude O. Iroh
Polymers 2023, 15(2), 299; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15020299 - 06 Jan 2023
Cited by 8 | Viewed by 1624
Abstract
Polyimide matrix nanocomposites have gained more attention in recent years due to their high thermal stability, good interfacial bonding, light weight, and good wear resistance and corrosion, factors that make them find great applications in the field of aerospace and advanced equipment. Many [...] Read more.
Polyimide matrix nanocomposites have gained more attention in recent years due to their high thermal stability, good interfacial bonding, light weight, and good wear resistance and corrosion, factors that make them find great applications in the field of aerospace and advanced equipment. Many advancements have been made in improving the thermal, mechanical, and wear properties of polyimide nanocomposites. The use of nanofillers such as carbon nanotubes, graphene, graphene oxide, clay, and alumina has been studied. Some challenges with nanofillers are dispersion in the polymer matrix and interfacial adhesion; this has led to surface modification of the fillers. In this study, the interaction between clay and graphene to enhance the thermal and thermal-oxidative stability of a nanocomposite was studied. A polyimide/graphene nanocomposite containing ~12.48 vol.% graphene was used as the base nanocomposite, into which varying amounts of clay were added (0.45–9 vol.% clay). Thermogravimetric studies of the nitrogen and air atmospheres showed an improvement in thermal decomposition temperature by up to 50 °C. The presence of both fillers leads to increased restriction in the mobility of polymer chains, and thus assists in char formation. It was observed that the presence of clay led to higher decomposition temperatures of the char formed in air atmosphere (up to 80 °C higher). This led to the conclusion that clay interacts with graphene in a synergistic manner, hence improving the overall stability of the polyimide/graphene/clay nanocomposites. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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19 pages, 6083 KiB  
Article
Thermal Degradation and Carbonization Mechanism of Fe-Based Metal-Organic Frameworks onto Flame-Retardant Polyethylene Terephthalate
by Tianyi Ma, Wenqing Wang and Rui Wang
Polymers 2023, 15(1), 224; https://0-doi-org.brum.beds.ac.uk/10.3390/polym15010224 - 01 Jan 2023
Cited by 3 | Viewed by 2211
Abstract
Currently, the metal-organic framework (MOF) is a promising candidate for flame−retardant polymers. In this study, a Fe−based MOF, MIL-88B(Fe), was introduced to polyethylene terephthalate (PET) and 3−hydroxyphenylphosphinyl-propanoic acid copolymer (P−PET) to reduce the fire hazard involved in using PET. The limiting oxygen indexes [...] Read more.
Currently, the metal-organic framework (MOF) is a promising candidate for flame−retardant polymers. In this study, a Fe−based MOF, MIL-88B(Fe), was introduced to polyethylene terephthalate (PET) and 3−hydroxyphenylphosphinyl-propanoic acid copolymer (P−PET) to reduce the fire hazard involved in using PET. The limiting oxygen indexes (LOIs) of MIL−PET and MIL−P−PET improved by 27% and 30%, respectively. The UL−94 level achieved for MIL−P−PET was V−0 rating. The thermal degradation and carbonization mechanisms of MIL−PET and MIL−P−PET were systematically investigated through thermogravimetric analysis coupled with a Fourier transform infrared spectroscopy (TG−IR), pyrolysis-gas chromatography−mass spectrometry (Py−GC−MS), x−ray photoelectron spectroscopy (XPS), and Raman spectrum combined with quantum chemical molecular dynamics simulation. With the addition of MIL−88B(Fe), high graphitization and a hard flammability char residual were generated. Compared with neat PET, the ferric ions efficiently catalyzed the homolytic cleavage and dehydrogenation of PET to produce a large amount of CO2 and terephthalic acid for MIL−PET in gas phase. Rough and hierarchical char residual with ferric oxide was also generated when temperatures exceeded 600 °C. However, the carbonization process was inhibited due to the coordinated complex between phosphorus and ferric ions in MIL−P−PET, invaliding the decarboxylation and generating more benzoic acid and its precursor, which led to heavy smoke. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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9 pages, 2829 KiB  
Communication
Thermal Degradation Behavior of Thiol-ene Composites Loaded with a Novel Silicone Flame Retardant
by Haonan Chen, Sheng Zhu, Rongfan Zhou, Xintong Wu, Wangyang Zhang, Xiaoshuai Han and Jiangbo Wang
Polymers 2022, 14(20), 4335; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14204335 - 14 Oct 2022
Cited by 4 | Viewed by 1401
Abstract
A novel silicone flame retardant PMDA was synthesized and blended with a commercial thiol–ene (TE) to obtain a flame-retardant TE (FRTE) composite. The cone calorimeter measurement showed the incorporation of PMDA improved the flame retardancy of the TE composite at concentrations of 5 [...] Read more.
A novel silicone flame retardant PMDA was synthesized and blended with a commercial thiol–ene (TE) to obtain a flame-retardant TE (FRTE) composite. The cone calorimeter measurement showed the incorporation of PMDA improved the flame retardancy of the TE composite at concentrations of 5 wt%. The thermal stability and degradation mechanism of FRTE in nitrogen was studied by thermogravimetric analysis. The degradation behaviour of TE containing a PMDA flame retardant was found to be changed. The kinetics of thermal degradation was evaluated by Kissinger method and Flynn–Wall–Ozawa method. The results showed that the activation energies of the FRTE degradation were higher than those of neat TE. However, the degradation mechanism of the TE matrix was not changed by the incorporation of flame-retardant PMDA. In this study, the flame-retardant mechanism of PMDA flame-retardant TE polymer was explained by using two kinetic analysis methods. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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29 pages, 10317 KiB  
Article
Fully Coupled Three-Dimensional Simulation of Downward Flame Spread over Combustible Material
by A. Snegirev, E. Kuznetsov, O. Korobeinichev, A. Shmakov, A. Paletsky, V. Shvartsberg and S. Trubachev
Polymers 2022, 14(19), 4136; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14194136 - 02 Oct 2022
Cited by 3 | Viewed by 1412
Abstract
Three-dimensional simulations of laminar flame propagating downwards the vertical surface of a rigid polyurethane slab heated by a radiative panel are presented and compared with the measurement data. The gas-phase model (ANSYS Fluent) allows for finite-rate volatile oxidation, soot formation and oxidation, emission, [...] Read more.
Three-dimensional simulations of laminar flame propagating downwards the vertical surface of a rigid polyurethane slab heated by a radiative panel are presented and compared with the measurement data. The gas-phase model (ANSYS Fluent) allows for finite-rate volatile oxidation, soot formation and oxidation, emission, transfer, and absorption of thermal radiation. The solid-phase model Pyropolis considers heat transfer across the material layer and generation of combustible volatiles in thermal decomposition of the material. Kinetic model of material decomposition is derived to obey the microscale combustion calorimetry data for different heating rates. Transient behavior of propagating flame and pyrolysis zone, as well as spatial distributions of heat flux components, temperature, and mass burning rates over the specimen surface are examined. Variation of the thermal properties of the material during its thermal decomposition, as well as the specimen surface emissivity and reradiation are shown to be the important issues strongly affecting model predictions. Two distinct modes of counterflow flame spread, thermal and kinetic, are identified. In the thermal mode corresponding to fast chemistry in the gaseous flame, the flame propagation velocity is governed by the heating rate of the combustible material ahead of the flame front. Alternatively, in the kinetic mode, it is limited by the burning velocity of the volatile-air mixture forming ahead of the flame front. Simulation results are favorably compared with the measured propagation velocity. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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12 pages, 2576 KiB  
Article
Effects of Nanofillers Based on Cetyltrimethylammonium-Modified Clays in a Polypropylene Nanocomposite
by Hyeon-Ju Ryu, Nguyen Thu Hang, Sanoj Rejinold. N, Byeongmoon Jeong, Goeun Choi and Jin-Ho Choy
Polymers 2022, 14(19), 4110; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14194110 - 30 Sep 2022
Cited by 2 | Viewed by 1267
Abstract
Nanocomposites of hydrophobic organo-clay/polypropylene (organo-clay/PP) were efficiently developed through a solution-blending technique. For this, we utilized various smectite clays as host agents; namely, Na-montmorillonite (Mt, ~1000 nm), Na-fluorine mica (Mica, ~1500 nm), and Na-hectorite (Ht, ~60 nm) with varied sizes, layer charges, and [...] Read more.
Nanocomposites of hydrophobic organo-clay/polypropylene (organo-clay/PP) were efficiently developed through a solution-blending technique. For this, we utilized various smectite clays as host agents; namely, Na-montmorillonite (Mt, ~1000 nm), Na-fluorine mica (Mica, ~1500 nm), and Na-hectorite (Ht, ~60 nm) with varied sizes, layer charges, and aspect ratios. Such clays were functionalized with cetyltrimethylammonium (CTA) bromide via an intercalation technique to obtain hydrophobic organic clays. The as-made clay particles were further mixed with a PP/xylene solution; the latter was removed to obtain the final product of the CTA-clay/PP nanocomposite. An X-ray diffraction (XRD) analysis confirmed that there were no characteristic (001) diffraction peaks for CTA-Mica in the PP nanocomposites containing CTA-Mica, assuring the fact that the Mica layers could be completely exfoliated and thereby homogenously composited within the PP. On the other hand, the CTA-Mt and CTA-Ht incorporated composites had broader (001) peaks, which might have been due to the partial exfoliation of CTA-Mt and CTA-Ht in the composites. Among the three CTA-clay/PP nanocomposites, the CTA-Mica nanohybrid showed an enhanced thermal stability by ~42 °C compared to the intact host polymer matrix. We also noted that when the CTA-Mica content was ~9 mass % in the nanocomposites, the Young’s modulus was drastically maximized to 69%. Our preliminary results therefore validated that out of the three tested clay-PP nanocomposites, the CTA-Mica nanofiller served as the best one to improve both the thermal and mechanical properties of the PP nanocomposites. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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15 pages, 4816 KiB  
Article
Effects of Phosphorus and Boron Compounds on Thermal Stability and Flame Retardancy Properties of Epoxy Composites
by Corneliu Hamciuc, Tăchiță Vlad-Bubulac, Diana Serbezeanu, Ana-Maria Macsim, Gabriela Lisa, Ion Anghel and Ioana-Emilia Şofran
Polymers 2022, 14(19), 4005; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14194005 - 24 Sep 2022
Cited by 9 | Viewed by 2078
Abstract
While plastics are regarded as the most resourceful materials nowadays, ranging from countless utilities including protective or decorating coatings, to adhesives, packaging materials, electronic components, paintings, furniture, insulating composites, foams, building blocks and so on, their critical limitation is their advanced flammability, which [...] Read more.
While plastics are regarded as the most resourceful materials nowadays, ranging from countless utilities including protective or decorating coatings, to adhesives, packaging materials, electronic components, paintings, furniture, insulating composites, foams, building blocks and so on, their critical limitation is their advanced flammability, which in fire incidents can result in dramatic human fatalities and irreversible environmental damage. Herein, epoxy-based composites with improved flame-resistant characteristics have been prepared by incorporating two flame retardant additives into epoxy resin, namely 6-(hydroxy(phenyl)methyl)-6H-dibenzo[c,e][1,2]oxaphosphinine-6-oxide (PFR) and boric acid (H3BO3). The additional reaction of 9,10-dihydro-oxa-10-phosphophenanthrene-10-oxide (DOPO) to the carbonyl group of benzaldehyde yielded PFR, which was then used to prepare epoxy composites having a phosphorus content ranging from 1.5 to 4 wt%, while the boron content was 2 wt%. The structure, morphology, thermal stability and flammability of resulted epoxy composites were investigated by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry (MCC). Thermogravimetric analysis indicated that the simultaneous incorporation of PFR and H3BO3 improved the thermal stability of the char residue at high temperatures. The surface morphology of the char residues, studied by SEM measurements, showed improved characteristics in the case of the samples containing both phosphorus and boron atoms. The MCC tests revealed a significant reduction in flammability as well as a significant decrease in heat release capacity for samples containing both PFR and H3BO3 compared to the neat epoxy thermoset. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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20 pages, 4817 KiB  
Article
Effect of Hygrothermal Ageing on the Mechanical and Fire Properties of a Flame Retardant Flax Fiber/Epoxy Composite
by Charlotte Campana, Romain Léger, Rodolphe Sonnier, Patrick Ienny and Laurent Ferry
Polymers 2022, 14(19), 3962; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14193962 - 22 Sep 2022
Cited by 3 | Viewed by 1383
Abstract
In engineering applications, natural fiber composites must comply with fire requirements including the use of flame retardant. Furthermore, biocomposites are known to be water sensitive. Whether flame retardants affect the water sensitivity and whether water absorption affects the fire behavior and the mechanical [...] Read more.
In engineering applications, natural fiber composites must comply with fire requirements including the use of flame retardant. Furthermore, biocomposites are known to be water sensitive. Whether flame retardants affect the water sensitivity and whether water absorption affects the fire behavior and the mechanical performance of biocomposites are the two main topics addressed in this work. In this study, a flax fiber/epoxy composite flame retardant with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or aluminum diethyl phosphinate (AlPi) was aged in humid atmosphere or by immersion in water. Water absorption kinetics revealed that DOPO induces an increase in equilibrium water content by approximately a factor of 2 due to its intrinsic hygroscopicity and/or its plasticizing effect on the epoxy matrix. In contrast, AlPi does not significantly change the water sensitivity of the biocomposite. Mechanical testing highlighted that, whatever the FR, the evolution of mechanical properties with ageing is governed by the moisture content. The drop of elastic modulus was attributed to a decrease in fiber rigidity due to plasticization, while the increase in tensile strength was assigned to an increase in fiber/matrix friction due to fiber swelling. As regards flame retardancy, only the highest water contents modified the fire behavior. For the AlPi containing biocomposite, the water release resulted in an increase by 50% of the time to ignition, while for the DOPO flame retardant biocomposite the water release was mainly postponed after ignition. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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13 pages, 1527 KiB  
Article
Thermally Resistant, Self-Extinguishing Thermoplastic Composites Enabled by Tannin-Based Carbonaceous Particulate
by André L. Missio, Rafael A. Delucis, Caio Gomide Otoni, Pedro H. G. de Cademartori, Rodrigo Coldebella, Arthur B. Aramburu, Bruno D. Mattos, Marlon B. B. Rodrigues, Nayara Lunkes, Darci A. Gatto and Jalel Labidi
Polymers 2022, 14(18), 3743; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14183743 - 07 Sep 2022
Cited by 4 | Viewed by 1531
Abstract
Flame-resistant materials are key components in buildings and several other engineering applications. In this study, flame retardancy and thermal stability were conferred to a highly flammable technical thermoplastic—polypropylene (PP)—upon compositing with a carbonaceous tannin-based particulate (CTP). Herein, we report on a straightforward, facile, [...] Read more.
Flame-resistant materials are key components in buildings and several other engineering applications. In this study, flame retardancy and thermal stability were conferred to a highly flammable technical thermoplastic—polypropylene (PP)—upon compositing with a carbonaceous tannin-based particulate (CTP). Herein, we report on a straightforward, facile, and green approach to prepare self-extinguishing thermoplastic composites by thermoblending highly recalcitrant particulate. The thermal stability and mechanical properties of the composites are tethered to the CTP content. We demonstrate that the addition of up to 65 wt% of CTP improved the viscoelastic properties and hydrophobicity of the PP, whereas having marginal effects on bulk water interactions. Most importantly, compositing with CTP remarkably improved the thermal stability of the composites, especially over 300 °C, which is an important threshold associated with the combustion of volatiles. PP-CTP composites demonstrated great capacity to limit and stop fire propagation. Therefore, we offer an innovative route towards thermally resistant and self-extinguishing PP composites, which is enabled by sustainable tannin-based flame retardants capable of further broadening the technical range of commodity polyolefins to high temperature scenarios. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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21 pages, 5264 KiB  
Article
Bio-Based Rigid Polyurethane Foams Modified with C-MOF/MWCNTs and TBPBP as Building Insulation Materials: Synergistic Effect and Corresponding Mechanism for Enhancing Fire and Smoke Safety
by Guangxu Bo, Xiaoling Xu, Xiaoke Tian, Jinyong Yan, Xingjian Su and Yunjun Yan
Polymers 2022, 14(17), 3630; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14173630 - 02 Sep 2022
Cited by 3 | Viewed by 1981
Abstract
Rigid polyurethane foams (RPUFs) as building insulation materials quickly burn and release a lot of heat, smoke, and carbon monoxide, and cause human safety risk and severe environmental pollution. To mitigate these disadvantages, MOF/MWCNTs were fabricated via mixing Cu ions’ partly substituted framework [...] Read more.
Rigid polyurethane foams (RPUFs) as building insulation materials quickly burn and release a lot of heat, smoke, and carbon monoxide, and cause human safety risk and severe environmental pollution. To mitigate these disadvantages, MOF/MWCNTs were fabricated via mixing Cu ions’ partly substituted framework of ZIF-67 and MWCNTs, and further calcinated MOF/MWCNTs (C-MOF/MWCTs) was newly generated by calcinating MOF/MWCNTs in air. Then, MOF/MWCNTs and C-MOF/MWCNTs were respectively employed together with a phosphorus–nitrogen-containing reactive flame retardant (TBPBP) to prepare renewable bio-based rigid polyurethane foam, including RPUF-T/MOF/MWCNTs 2 and RPUF-T/C-MOF/MWCNTs 2. The characterization results showed that RPUF-T/C-MOF/MWCNTs 2 had better performance than RPUF-T/MOF/MWCNTs 2 and neat RPUF. Compared to neat RPUF, the compressive strength, limiting oxygen index value, and the mass char residue in cone calorimetry test of RPUF-T/C-MOF/MWCNTs 2, respectively, were increased by 105.93%, 46.35%, and 347.32%; meanwhile, the total heat release rate, total smoke production, total carbon monoxide product, and total carbon dioxide product were reduced by 47.97%, 50.46%, 41.38%, 43.37%, respectively. This study provides a referable method for preparing RPUFs with good physical properties, fire, and smoke safety, which is favorable for human safety and environmental protection as new building insulation materials. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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16 pages, 4030 KiB  
Article
Preparation and Performances of Polyether Polytriazole Elastomers Based on Click Chemistry
by Kun Cong, Zhenhui Liu, Fa Hu, Jiyu He and Rongjie Yang
Polymers 2022, 14(17), 3538; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14173538 - 29 Aug 2022
Cited by 1 | Viewed by 1634
Abstract
Since the polyurethane elastomer synthesis process is susceptible to moisture, polytriazole polyethylene oxide-tetrahydrofuran (PTPET) elastomer was used as a replacement owing to its mild production environment. In contrast to the conventional flask-synthesis method, the twin-screw reactor instrument could provide more meaningful data in [...] Read more.
Since the polyurethane elastomer synthesis process is susceptible to moisture, polytriazole polyethylene oxide-tetrahydrofuran (PTPET) elastomer was used as a replacement owing to its mild production environment. In contrast to the conventional flask-synthesis method, the twin-screw reactor instrument could provide more meaningful data in the synthesis. In this study, PTPET elastomer was prepared by the MiniLab twin-screw reactor method for the first time, and the activation energy of the PTPET elastomer was calculated using the torque variation obtained from the MiniLab twin-screw reactor during the synthesis process at two different temperatures. The addition of flame retardants could endow the composites with more useful properties. The PTPET composites poly (phenylsilsesquioxane) (PTPET-PPSQ), octaphenyl polyhedral oligomeric silsesquioxane (PTPET-OPS) and PTPET-PhVPOSS (phenyl/vinyl polysilsesquioxane) were synthesized by using the MiniLab twin-screw reactor. The prepared PTPET elastomer and composites were fully characterized by FT-IR, TG, DSC, swelling test, mechanical test, SEM and combustion test. The characterization results show that the addition of the flame retardants has little influence on the original structure and properties of PTPET elastomer. The flame retardancy was characterized by the combustion test showing that all PTPET composites form a certain thickness of char layer during the burning process. These results indicate that the addition of flame retardants maintains the outstanding properties of PTPET elastomer and also endows the materials with a certain extent of flame retardancy; thus, it is believed to be a good engineering material that could be applied in many realms. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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18 pages, 4660 KiB  
Article
The Influence of Flame Retardants on Combustion of Glass Fiber-Reinforced Epoxy Resin
by Oleg Korobeinichev, Artem Shaklein, Stanislav Trubachev, Alexander Karpov, Alexander Paletsky, Anatoliy Chernov, Egor Sosnin and Andrey Shmakov
Polymers 2022, 14(16), 3379; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14163379 - 18 Aug 2022
Cited by 8 | Viewed by 2024
Abstract
For the first time, next to the flammability tests (LOI, UL-94 HB, VBB, TGA), experimental tests and computer simulation have been conducted on the flame spread and combustion of glass fiber-reinforced epoxy resins (GFRER) with 6% graphene and 6% DDM-DOPO flame-retardant additives. The [...] Read more.
For the first time, next to the flammability tests (LOI, UL-94 HB, VBB, TGA), experimental tests and computer simulation have been conducted on the flame spread and combustion of glass fiber-reinforced epoxy resins (GFRER) with 6% graphene and 6% DDM-DOPO flame-retardant additives. The downward rates of flame spread (ROS) in opposed flow with oxidizer and the upward ROS along GFRER composites have been first measured as well as the distribution of temperature over the combustion surface of the composites with flame-retardant additives and without them. The LOI and UL-94 HB tests showed a reduction in the flammability of GFRER when flame retardants were added and predicted a higher effectiveness of DDM-DOPO compared to graphene. Adding DDM-DOPO resulted in increasing the rate of formation of the volatile pyrolysis products and their yield, indicating, together with the other data obtained, the gas phase mechanism of the flame retardant’s action. Adding graphene resulted in an increase in the soot release on the burning surface and an increase in the amount of non-volatile pyrolysis products on the burning surface, reducing the amount of fuel that participated in the oxidation reactions in the gas phase. The developed numerical combustion model for GFRER with a DDM-DOPO additive, based on the action of DDM-DOPO as a flame retardant acting in the gas phase, satisfactorily predicts the effect of this flame retardant on the reduction in downward ROS over GFRER for 45–50% oxygen concentrations. The developed model for GFRER with graphene additive, based on a reduction in the amount of fuel and increase in the amount of incombustible volatile pyrolysis products when graphene is added, predicts with good accuracy downward ROS over GFRER depending on oxygen concentration. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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12 pages, 23673 KiB  
Article
Fire Behavior and Failure Model of Multilayered Wood Flour/HDPE/Polycarbonate Composites with a Sandwich Structure
by Jingfa Zhang, Ahmed Koubaa, Dan Xing, Haigang Wang, Yubo Tao, Xiang-Ming Wang and Peng Li
Polymers 2022, 14(14), 2833; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14142833 - 12 Jul 2022
Cited by 3 | Viewed by 1386
Abstract
The flame retardancy of wood–polymer composites significantly affects their potential applications. Thus, multilayered wood flour/high-density polyethylene (HDPE)/polycarbonate (PC) composites were prepared via thermocompression to improve the fire retardancy of wood–polymer composites in this paper. Thermal degradation behavior, flame retardancy, and flexural strengths of [...] Read more.
The flame retardancy of wood–polymer composites significantly affects their potential applications. Thus, multilayered wood flour/high-density polyethylene (HDPE)/polycarbonate (PC) composites were prepared via thermocompression to improve the fire retardancy of wood–polymer composites in this paper. Thermal degradation behavior, flame retardancy, and flexural strengths of the resulting composites were investigated using a thermogravimetric analysis, cone calorimetry, and mechanical testing machine, respectively. Results revealed that the boric acid treatment reduced the heat release rate and total heat release of the wood flour/HDPE composites and increased their mass of residues. However, boric acid reduced the flexural strength of the resulting composites. The combustion test indicated that PC cap layers suppressed the combustion of the resulting composites via the formation of carbon layers. Adding PC layers reduced heat release and increased the flexural strength of the resulting composites. Finally, the failure mode of the multilayered wood flour/HDPE/PC composites in the three-point flexural test was simulated by finite element analysis. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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20 pages, 11729 KiB  
Article
Investigation of Efficient Alkali Treatment and the Effect of Flame Retardant on the Mechanical and Fire Performance of Frost-Retted Hemp Fiber Reinforced PLA
by Percy Festus Alao, Raimond Press, Heikko Kallakas, Jussi Ruponen, Triinu Poltimäe and Jaan Kers
Polymers 2022, 14(11), 2280; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14112280 - 03 Jun 2022
Cited by 7 | Viewed by 1933
Abstract
This research investigates an effective alkali (NaOH) treatment and fire-retardant coating to produce biocomposites from frost-retted hemp fiber and PLA. The fiber surface treatment with various NaOH concentrations was investigated throughout a range of soaking times. The results show that the extracted non-cellulosic [...] Read more.
This research investigates an effective alkali (NaOH) treatment and fire-retardant coating to produce biocomposites from frost-retted hemp fiber and PLA. The fiber surface treatment with various NaOH concentrations was investigated throughout a range of soaking times. The results show that the extracted non-cellulosic fiber content increases with treatment duration and NaOH concentration, while the fraction of targeted components removed remains nearly unchanged after soaking for 1, 2, and 4 h with a 5 wt.% NaOH solution. At the composite level, the treatment with 5 wt.% NaOH solution for 1 h emerged as the most efficient, with tensile strength, Young’s modulus, flexural strength, and flexural modulus of 89.6 MPa, 9.1 GPa, 121.6 MPa, and 9.6 GPa, respectively, using 30 wt.% fibrous reinforcement. The fire performance of the examined batches of biocomposites improved significantly with the novel fire-retardant (Palonot F1) coating. However, the tensile strength notably decreased, while the flexural properties showed only a slight reduction. In most cases, the biocomposites with the alkali-treated hemp fiber had delayed ignition during the 5 min exposure to the cone heater. The findings in this work contribute to studies that will be required to give design guidelines for sustainable building options. Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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22 pages, 4690 KiB  
Article
Flame-Retarding Properties of Injected and 3D-Printed Intumescent Bio-Based PLA Composites: The Influence of Brønsted and Lewis Acidity of Montmorillonite
by Raíssa Carvalho Martins, Simone Pereira da Silva Ribeiro, Michelle Jakeline Cunha Rezende, Regina Sandra Veiga Nascimento, Marco Antonio Chaer Nascimento, Marcos Batistella and José-Marie Lopez-Cuesta
Polymers 2022, 14(9), 1702; https://0-doi-org.brum.beds.ac.uk/10.3390/polym14091702 - 21 Apr 2022
Cited by 9 | Viewed by 1597
Abstract
The influence of processing intumescent bio-based poly(lactic acid) (PLA) composites by injection and fused filament fabrication (FFF) was evaluated. A raw (ANa) and two acidic-activated (AH2 and AH5) montmorillonites were added to the intumescent formulation, composed by lignin and ammonium polyphosphate, in order [...] Read more.
The influence of processing intumescent bio-based poly(lactic acid) (PLA) composites by injection and fused filament fabrication (FFF) was evaluated. A raw (ANa) and two acidic-activated (AH2 and AH5) montmorillonites were added to the intumescent formulation, composed by lignin and ammonium polyphosphate, in order to evaluate the influence of the strength and the nature (Brønsted or Lewis) of their acidic sites on the fire behavior of the composites. The thermal stability and the volatile thermal degradation products of the composites were assessed. The injected and 3D-printed composites were submitted to cone calorimeter (CC), limit oxygen index (LOI), and UL-94 flammability tests. A similar tendency was observed for the injected and 3D-printed samples. The high density of strong Lewis sites in AH2 showed to be detrimental to the fire-retarding properties. For the CC test, the addition of the intumescent composite reduced the peak of heat released (pHRR) in approximately 49% when compared to neat PLA, while the composites containing ANa and AH5 presented a reduction of at least 54%. However, the addition of AH2 caused a pHRR reduction of around 47%, close to the one of the composite without clay (49%). In the LOI tests, the composites containing ANa and AH5 achieved the best results: 39% and 35%, respectively, for the injected samples, and 35 and 38% for the 3D-printed samples. For the composite containing AH2 the LOI values were 34% and 32% for injected and 3D-printed samples, respectively. Overall, the best performance in the flammability tests was achieved by the composites containing clays with only weak and moderate strength acidic sites (ANa and AH5). Full article
(This article belongs to the Special Issue Flame-Retardant Polymer Composites)
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