Pyrolysis Combustion Flow Calorimeter Research Articles

Cage Nanofillers' Influence on Fire Hazard and Toxic Gases Emitted during Thermal Decomposition of Polyurethane Foam.

Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH3, CO and CO2. According to the literature review, complex studies on the fire hazard of a system of POSS-phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS-phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

Influence of char‐forming lignin in combination with aluminium phosphinate on thermal stability and combustion properties of polyamide 11 blends

AbstractPolyamide 11 (PA) blends based on char‐forming industrial lignin and aluminum phosphinate (AlP) were prepared to improve flame retardant (FR) properties using a green and eco‐friendly approach. This study investigates the thermal degradation and combustion behavior of PA blends prepared by using AlP in combination with two different types of industrial lignins (i.e., kraft lignin (DL) and lignosulphonate lignin (LL). Thermogravimetric (TG) analysis showed that ternary blends containing LL and AlP developed higher char residue up to 10.7 wt% upon decomposition in inert atmospheres. The combination of lignin and AlP increases the thermal stability by shifting the initial decomposition temperature (T5%) and temperature at maximum decomposition (Tmax) to a higher temperature range, attributed to the stabilization of decomposition products. Furthermore, combustion behavior studied by cone calorimeter (forced combustion) and pyrolysis combustion flow calorimeter (PCFC) tests presented a significant reduction in the peak of heat release rate (PHRR) and total heat release (THR). It was found that LL and AlP‐containing blends more effectively decreased fire parameters like PHRR and THR than that of DL and AlP‐containing blends. The best interaction with reduced fire‐retardant properties was obtained when 10 wt% loading of lignin (DL/LL) and AlP was used. The reduction in heat release parameters was mainly ascribed to the condensed phase mechanism by forming an efficient protective char layer, which acts as a barrier against heat and mass transfer between the condensed and the gas phases. Raman spectroscopy analysis also confirmed the formation of the protective graphitic layer in the condensed phase.

Flame retardancy of sustainable polylactic acid and polyhydroxybutyrate (PLA/PHB) blends

Nowadays, development of new biobased/biodegradable polymers from biological resources is of great interest from a sustainability standpoint. Polyhydroxybutyrate (PHB) and polylactic acid (PLA) are two biopolymers obtained from renewable resources. In this study, the flame-retardant effect of a newly developed flame retardant (FR) based on melamine in a PLA/PHB blend was studied. Several combinations containing this new FR combined with ammonium polyphosphate (APP) and sepiolite were introduced in a PLA/PHB blend. 20 wt% of FR were introduced into a matrix containing 75 wt% PLA and 25 wt% PHB blended with a microcompounder. According to pyrolysis combustion flow calorimeter (PCFC) analyses, all the FR formulations exhibited reduced flammability. The results revealed a considerable decrease in the peak of heat release rate (pHRR) by 33 % in the presence of the new FR while a reduction of about 60 % for combinations with APP and sepiolite. The new FR system significantly enhanced the fire behaviour of PLA/PHB blend. The work presents the first cone calorimeter analyses of PLA/PHB composites. The fire behaviour evolved from thin sample to a thick charring behaviour highlighted by an increase of the residue after cone calorimeter from 0 to 14.7 % with this FR system.

How phosphinated hydroxyurethane groups improve chemical resistance and flame retardant properties of alkyd resins?

A novel phosphorus containing polyhydroxyurethane (PHU) oligomer (DGGDAC-MXDA-DOPO), has been synthetized and grafted onto the remaining acid groups of alkyd resins in order to obtain hybrid poly(alkyd hydroxyurethane) (PAHU) resins with flame retardant properties. PAHU resins have demonstrated better alkali resistance than pure alkyd resins without PHU oligomer. Moreover, the grafting of PHU onto alkyd resin through the formation of amide bonds has exhibited thixotropic properties. The thermal and flame retardancy properties have been investigated through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The alkyd resins were applied as a coating on a wood surface and fire behavior was tested by cone calorimeter analysis. The most effective coating, by taking into account, the film properties and the flame retardant behavior contains 24 wt% of PHU (1.5 wt% P) and exhibited a 40% reduction in peak of Heat Release Rate (pHRR) compared to the resins without PHU.

Triple Benefits of Cardanol as Chain Stopper, Flame Retardant and Reactive Diluent for Greener Alkyd Coating

Cardanol, a waste from the food industry and widely produced (1 Mt/y), has been used as a chain stopper during the polycondensation of short oil alkyd resins in order to replace benzoic acid. Then, phosphorylated cardanol has been added in order to both reduce solvent content and bring flame-retardant (FR) properties to the alkyd resins. The renewable carbon content of the formulations has been increased up to 23%. The impact of the introduction of phosphorylated cardanol molecules on the drying time and flexibility has been studied as well as the thermal and flame-retardant properties by differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The most effective flame-retardant coating that was associated with excellent FR properties and excellent coating properties has been obtained with phosphate-cardanol added at 2%wt of P. Indeed, the film properties were closed to the classical alkyd resin, the solvent content was reduced by 50% and the pHRR decreased by 42% compared to the reference alkyd resin.

Use of fly ash as synergistic and reactive component of flame retardant system in polylactide

For a long time, fly ash has been considered as pure waste of coal power plants. Nevertheless, unique properties and compositions that vary with the material's origin make fly ash appealing as an engineering material in various applications. Thus, the opportunity to reduce the environmental footprint of polylactide through the incorporation of fly ash as a component of flame retardant systems has been investigated. Combinations of fly ash with ammonium polyphosphate and/or melamine polyphosphate were made for a global loading of 25 wt% with various rates of substitution of the flame retardants. Fire performance has been studied from cone calorimeter experiments as well as the use of pyrolysis combustion flow calorimeter (PCFC) and the UL94V test. The interpretation of the fire retardant mechanisms has been performed through the examination of cone calorimeter residues by scanning electronic microscopy, X-ray microanalysis, X-ray diffraction (XRD) and multinuclear solid-state NMR. It can be shown that fly ash is mainly composed of spherical particles which are thermally stable at cone calorimeter tests when used alone in PLA. Conversely, fly ash behaves as a reactive component with both flame retardants, leading to the formation of new crystalline and amorphous compounds as shown by XRD and NMR. Synergistic effects in fire performance resulting from the reactive behavior of fly ash can be highlighted and are ascribed to fire retardant mechanisms acting in the condensed phase, and corresponding to the conservation of high phosphorus contents in the condensed phase.

Influence of Phosphorus Structures and Their Oxidation States on Flame-Retardant Properties of Polyhydroxyurethanes.

This article focuses on the synthesis of polyhydroxyurethane (PHU) materials containing novel phosphorus flame retardants (FR). Four different phosphorus compounds were grafted onto cyclic carbonate: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diethyl phosphite (DEP), diphenyl phosphite (DPP) and dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO). Thus, three novel phosphorus reactive cyclic carbonates which have never been reported so far were synthetized. Phosphorus FR containing PHU materials were characterized by FTIR to evidence the total conversion of the cyclic carbonate. Moreover, the gel contents up to 80% confirmed the formation of the polymer network. Then, the thermal stability and the flame-retardant properties were investigated by thermogravimetric analyses, cone calorimeter and pyrolysis combustion flow calorimeter. The mode of action of phosphorus compounds, depending on the oxidation state, was especially highlighted. Phosphonate (+III) provided better action in a condensed phase than phosphinate thanks to a more efficient char formation. Among phosphonates, differences were observed in terms of char-formation rate and expansion. DEP provided the best flame-retardant properties, with a reduction of 76% of pHRR with 2 wt% of phosphorus in cone calorimeter analysis. Therefore, this article highlighted the different modes of action of phosphorus flame retardants, depending on the oxidation state of phosphorus, in PHU materials.

Synergistic effect of DOPO and VMDMS for flame retardancy of alkyd resins

New polysiloxane oligomers containing phosphorus, 6-(2-(dihydroxy(methyl)silyl)ethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DOPO-VMDMS), have been synthetized and grafted to the remaining hydroxyl groups of alkyd resins in order to obtain hybrid alkyd resins with flame retardant properties. These silicone alkyd resins have demonstrated better drying time, gloss and chemical resistance than reference alkyd resins without DOPO-VMDMS. Moreover, the thermal and flame retardancy properties have been investigated using differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The alkyd resins were applied as a coating on wood and fire behavior was tested by cone calorimeter analysis. The most effective coating contains 30 wt% DOPO-VMDMS and exhibited a 55 % reduction in pHRR compare to the resins without DOPO-VMDMS.

Phosphorus Modified Cardanol: A Greener Route to Reduce VolaTile Organic Compounds and Impart Flame Retardant Properties to Alkyd Resin Coatings.

Novel phosphorylated cardanol molecules based on phosphonate (PO3CR) and phosphate (PO4CR) functions were synthetized. Those molecules have two main actions which are described in this article: the reduction in volatile organic compounds (VOC) and the development of flame retardant (FR) properties conferred on alkyd resins used as coatings for wood specimen. Phosphorylated cardanol compounds have been successfully grafted by covalent bonds to alkyd resins thanks to an auto-oxidative reaction. The impact of the introduction of PO3CR and PO4CR on the film properties such as drying time and flexibility has been studied and the thermal and flame retardant properties through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. These studies underscored an increase in the thermal stability and FR properties of the alkyd resins. In the cone calorimeter test, the lowest pHRR was obtained with 3 wt% P of phosphate-cardanol and exhibited a value of 170 KW.m−2, which represented a decrease of almost 46% compared to the POxCR-free alkyd resins. Moreover, a difference in the mode of action between phosphonate and phosphate compounds has been highlighted. The most effective coating which combined excellent FR properties and good coating properties has been obtained with 2 wt% P of phosphate-cardanol. Indeed, the film properties were closed to the POxCR-free alkyd resin and the pHRR decreased by 41% compared to the reference alkyd resin.

Synthesis of reactive phosphorus-based carbonate for flame retardant polyhydroxyurethane foams

Polyurethane (PU) foams are widely used for many applications, however the use of toxic isocyanate monomers for their synthesis has recently led researchers to non-isocyanate PU foams. The most promising alternative is the aminolysis of cyclic carbonate which yields polyhydroxyurethanes (PHU). Nevertheless, the obtained foams suffer from significant flammability and require the introduction of flame retardants to improve their flame retardant properties. Hence, this article demonstrates the first synthesis of PHUs foams containing phosphorus-based flame retardants. The flame retardant were allowed to react with the monomers to prevent any leaching from the foams. Moreover, several structures of cyclic carbonates were analyzed in order to determine the influence of aromatic rings on both thermal stability and mechanical properties of foams by thermogravimetric analyses, differential scanning calorimetry and dynamic mechanical analyses. The flame retardant properties were studied with a cone calorimeter and pyrolysis combustion flow calorimeter. The best results were obtained by the foam containing 2 wt% of phosphorus and two aromatic rings in the cyclic carbonate structure. Cone calorimeter analysis showed a total heat release of 13.1 KJ.g−1 versus 19.1 KJ.g−1 for the DOPO-free foam.

Synergic flame-retardant effect of cellulose nanocrystals and magnesium hydroxide in polyurethane wood coating

In this paper, a wood coating based on waterborne polyurethane (WPU)/nano-cellulose crystalline (CNC)/Magnesium hydroxide (MH) was prepared. Efficient dispersion of MH in WPU in presence of 5 wt% of CNCs was observed by biological microscope leading to a material with improved esthetic, thermal and fire-retardant properties and mechanical performance. By thermogravimetric analysis (TG/DTG) and comparison with WPU, the maximum weight loss rate (RTmax) of WPU/CNC/MH coating decreased dramatically from 13.2 to 6.63, and the residue increased sharply from 4.69% to 40.55%. The results of pyrolysis combustion flow calorimeter (PCFC) showed that the flame-retardant performance of the composite coating is also greatly improved, and the peak of heat rate release (pHRR) being reduced from 350 w/g to 121 w/g. When applied to the wood panels, according to the Limiting oxygen index (LOI) experiment, for MH < 40 wt%, the combustibility grade is B2 level (combustible material), whereas for MH > 40 wt% the grade is B1 level (flame retardant material).

A method to quantitatively assess the modes-of-action of flame-retardants

The assessment of the modes of action of flame retardants (FRs) and their quantification is a challenging issue. This study highlights that the condensed phase efficiency θ can be assessed by combining different flammability tests (pyrolysis-combustion flow calorimeter PCFC, Limiting Oxygen Index LOI, cone calorimeter). Relations were proposed to calculate LOI and pHRR in cone calorimeter from several parameters including θ. A satisfying agreement between experimental values and calculated ones were found for a set of several dozens of FR-free polymers assuming that θ = 1 (i.e. no action in condensed phase).Then, θ was evaluated for EVA/PE blends containing Aluminium TriHydroxyde (ATH) and/or Magnesium DiHydroxyde (MDH) and for ABS containing Ammonium PolyPhosphate (APP) and/or DecaBromoDiPhenylOxide (DBDPO) assuming that LOI and pHRR of flame-retardant compositions follow the same relationships as those of unfilled polymers. The evolution of θ (as well as χ, i.e. the combustion efficiency) highlights the modes of action of FRs and can contribute to the discussion about possible synergy or antagonism between FRs. Especially, an apparent synergism between APP/DBDPO is observed in cone calorimeter from a performance point of view. Nevertheless, the calculation of χ and θ challenges this conclusion.

Coffee Wastes as Sustainable Flame Retardants for Polymer Materials

Development of green flame retardants has become a core part of the attention of material scientists and technologists in a paradigm shift from general purpose to specific sustainable products. This work is the first report on the use of coffee biowastes as sustainable flame retardants for epoxy, as a typical highly flammable polymer. We used spent coffee grounds (SCG) as well as SCG chemically modified with phosphorus (P-SCG) to develop a sustainable highly efficient flame retardant. A considerable reduction in the peak of heat release rate (pHRR) by 40% was observed in the pyrolysis combustion flow calorimeter analysis (PCFC), which proved the merit of the used coffee biowastes for being used as sustainable flame retardants for polymers. This work would open new opportunities to investigate the impact of other sorts of coffee wastes rather than SCG from different sectors of the coffee industry on polymers of different family.

Flame retardancy effect of phosphorus graphite nanoplatelets on ethylene‐vinyl acetate copolymer: Physical blending versus chemical modification

AbstractA novel modified exfoliated graphite nanoplatelets (GNP‐g‐APP), resulting from grafting ammonium polyphosphate (APP) on exfoliated graphite nanoplatelets (GNP) was prepared and evaluated as flame retardant for ethylene‐vinyl acetate copolymer (EVA). The effect of modification on the thermal stability and flame retardancy of EVA was discussed. Thermogravimetric analysis (TGA), UL‐94, pyrolysis combustion flow calorimeter (PCFC), and mass loss calorimeter (MLC) analyses were employed for the evaluation of the thermal stability and flame retardancy of composites. The introduction of 20 wt.% GNP‐g‐APP into EVA resulted in significant enhancement in flame retardant properties with respect to the system containing physical mixture of GNP and APP. The former blend exhibited 57% decrease in the peak of heat release rate (pHRR), and 35% reduction in the total heat release (THR) than the latter one in MLC test. Thus, pHRR was decreased from 940 kW.m−2 for neat EVA to 403 kW.m−2 for EVA containing GNP‐g‐APP. V0 rating (auto‐extinguishable behavior) was also observed in UL 94 chemically modified sample. According to the present study, chemical modification of GNP with APP is more effective than a physical mixing of GNP and APP in improving the flame retardant properties of EVA.

Effectiveness of Silanization and Plasma Treatment in the Improvement of Selected Flax Fibers' Properties.

The study investigated the effectiveness of the combination of chemical and physical methods of natural fibers’ modification. The long flax fibers were subjected to various types of modification. These were silanization, plasma modification and a combination of these methods. For the silanization process, two types of silanes were used: amino- and vinylsilane. The application of structurally different compounds allowed us to acquire knowledge about the effect of the modifier structure on its properties. Various properties of flax fibers were investigated, comparing the results before and after different modification processes. The flammability of prepared samples were tested by pyrolysis combustion flow calorimeter (PCFC). In the effect of the natural fibers’ modifications, flammability was reduced even by 30%. The thermal stability of modified fibers increased. The FTIR tests of the gases released during thermal degradation of the tested fibers allowed us to determine the important compounds and prove a lower degree of flax-fiber decomposition after modification. Flax fibers were also tested to evaluate their physical properties (linear mass, average diameter, aspect ratio and hygroscopicity). Changes in surface morphology were observed by scanning electron microscope (SEM). The properties of natural fibers improved significantly, thus contributing to an increase in their suitability for the use in composites.

Fire behavior of lead-containing PMMA based Kyowaglas

In the present work, the flammability of Kyowaglas is characterized experimentally. Kyowaglas is a lead-based composite used in glove boxes of nuclear facilities as a biological protection against radiation. It consists of 70%wt PMMA (Poly(Methyl Methacrylate)) and 30%wt leaded compounds. The aim of the study is to understand the role and impact of lead during the combustion of Kyowaglas in order to deepen knowledge of its thermal and fire behavior. A comparative study between Kyowaglas and virgin PMMA is conducted to better understand the effect of lead on the combustion process of these materials. Fire behavior is studied using cone calorimeter, pyrolysis-combustion flow calorimeter and thermogravimetric analysis. At different stages of cone calorimeter test, the samples and residues were examined and characterized using different experimental techniques like microscopy, spectroscopy, X-ray diffraction and calorimetry. Thermal analysis data show that lead seems to slightly accelerate the decomposition of PMMA under inert atmosphere. However, it confers significant thermal stability during a cone test due to the accumulation of lead on the surface of the sample. As the Kyowaglas burns, metallic lead is formed and accumulated at the top surface slowing down the heat transfer. At the end of the cone calorimeter test, lead oxide beads start to form on the surface of the residue due to the oxidation of metallic lead.

Dual UV-Thermal Curing of Biobased Resorcinol Epoxy Resin-Diatomite Composites with Improved Acoustic Performance and Attractive Flame Retardancy Behavior

This study has developed novel fully bio-based resorcinol epoxy resin–diatomite composites by a green two-stage process based on the living character of the cationic polymerization. This process comprises the photoinitiation and subsequently the thermal dark curing, enabling the obtaining of thick and non-transparent epoxy-diatomite composites without any solvent and amine-based hardeners. The effects of the diatomite content and the compacting pressure on microstructural, thermal, mechanical, acoustic properties, as well as the flame behavior of such composites have been thoroughly investigated. Towards the development of sound absorbing and flame-retardant construction materials, a compromise among mechanical, acoustic and flame-retardant properties was considered. Consequently, the composite obtained with 50 wt.% diatomite and 3.9 MPa compacting pressure is considered the optimal composite in the present work. Such composite exhibits the enhanced flexural modulus of 2.9 MPa, a satisfying sound absorption performance at low frequencies with Modified Sound Absorption Average (MSAA) of 0.08 (for a sample thickness of only 5 mm), and an outstanding flame retardancy behavior with the peak of heat release rate (pHRR) of 109 W/g and the total heat release of 5 kJ/g in the pyrolysis combustion flow calorimeter (PCFC) analysis.

Combined effect of palygorskite and melamine polyphosphate on flame retardancy properties of polyamide 11 nanocomposites

Pyrolysis and fire behaviour of palygorskite (Pal) fibrous clay (5 wt%) reinforced polyamide 11 nanocomposites prepared by melt compounding were investigated in combination with melamine polyphosphate (MPP). Palygorskite was modified by 3-amino-propyl-triethoxysilane (APTES). Thermal stability and combustion behaviour of the materials were studied by thermogravimetric analysis (TGA), pyrolysis combustion flow calorimeter (PCFC) and cone calorimeter. TGA data showed that MPP reduced the thermal stability of PA11 nanocomposites, whereas the addition of both unmodified and modified palygorskite improved this property. Further, the cone calorimeter and PCFC results indicated a significant decrease in the peak of heat release rate (pHRR) and the total heat release (THR) of PA11 nanocomposites. This also means that the PA11 combustion was strongly reduced in the presence of combined Pal with MPP, being however more pronounced for the modified palygorskite. The improved fire behaviour could be attributed to a synergistic effect between Pal and MPP.

Influence of Sepiolite and Lignin as Potential Synergists on Flame Retardant Systems in Polylactide (PLA) and Polyurethane Elastomer (PUE).

A comparison of the influence of sepiolite and lignin as potential synergists for fire retardant (FR) systems based on ammonium polyphosphate (APP) has been carried out in polyurethane elastomer and polylactide. Different ratios of kraft lignin and sepiolite were tested in combination with APP in both polymers. The thermal stability and the fire behavior of the corresponding composites were evaluated using Thermogravimetric Analysis (TGA), a Pyrolysis Combustion Flow Calorimeter (PCFC) and Cone Calorimeter (CC). The mechanisms of flame retardancy imparted by APP and other components were investigated. Synergistic effects were highlighted but only for specific ratios between APP and sepiolite in polyurethane elastomer (PUE) and polylactide (PLA) on one hand, and between APP and lignin in PLA on the other hand. Sepiolite acts as char reinforcement but through the formation of new phosphorus compounds it is also able to form a protective layer. Conversely, only complementary effects on fire performance were noted for lignin in PUE due to a dramatic influence on thermal stability despite its action on char formation.

Improving the flame retardant properties of polyester‐cotton blend fabrics by introducing an intumescent coating via layer by layer assembly

AbstractLayer by layer (LBL) assembly technique was used to deposit multilayer coating containing phosphorus‐nitrogen onto the surface of fibers to improve the flame retardancy of polyester‐cotton (PET‐COT) blended fabric. Ellipsometer results confirmed that polyallylamine hydrochloride (PAH), melamine (MEL), and ammonium polyphosphate (APP) grew linearly on silicon wafer during the LbL process. The LOI value of coated PET‐COT fabric was increased from 20.8% of pristine fabric to 28.4% by the presence of about 9 wt% coating. Besides, this intumescent nanocoated PET‐COT fabric was self‐distinguished during the vertical burning test. Thermogravimetric analysis under both nitrogen and air atmosphere revealed that the initial degradation temperature of the coated sample was decreased and the char residue amount was significantly improved during combustion. The flame resistance performance evaluation by pyrolysis combustion flow calorimeter indicated that this coating effectively reduced the peak heat release rate of PET‐COT matrix. The scanning electron micrographs of char residue demonstrated that the char formation in the condensed phase and free radical caption in the gas phase was responsible for the improved flame retardancy. It is suggested this unique facile coating technology with low cycles and high efficiency has great potential to produce commercially available flame retardant polymeric‐cotton blend fabrics.