Polymer Degradation and Stability (v.113, #C)
Editorial Board (IFC).
Deterioration of contemporary and artificially aged cotton by selected fungal species by Katja Kavkler; Nina Gunde Cimerman; Polona Zalar; Andrej Demšar (1-9).
The scope of this study was an analysis of the deterioration of cotton fibres caused by selected strains of fungal species from historical cotton textile objects. Aged and non-aged cotton fabric specimens were inoculated with representative strains of the six highest frequency fungal species isolated from museum textile objects from different Slovene museums. The selected fungi were Aspergillus clavatus, Cladosporium cladosporoides, Fomes fomentarius, Hypoxylon fragiforme, Penicillium chrysogenum and Penicillium corylophilum. Their effects on contemporary and artificially aged cotton was examined by Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, and tensile behaviour. These fungal species affected the cellulose structure and fabric properties differently. Among the fungi analysed, P. chrysogenum was least harmful to cotton-cellulose samples, while C. cladosporoides, F. fomentarius and H. fragiforme showed the greatest effects. The main structural changes were hydrolysis, depolymerisation, and decreased molecular order. Although not all of these fungal species are dangerous to cotton fibres, and hence to museum objects, they all cause visible changes that can lead to disintegration of these objects. Another important factor that accelerates the depolymerisation of cellulose macromolecules in cotton fibre is inappropriate storage conditions, which should be avoided at all costs, to preserve historical objects and artefacts.
Keywords: Cotton; Biodeterioration; Fungi; Raman spectroscopy; Fourier transform infrared spectroscopy; Tensile properties;
Modeling color and chemical changes on normal and red heart beech wood by reflectance spectrophotometry, Fourier Transform Infrared spectroscopy and hyperspectral imaging by Giuseppe Bonifazi; Luca Calienno; Giuseppe Capobianco; Angela Lo Monaco; Claudia Pelosi; Rodolfo Picchio; Silvia Serranti (10-21).
The use of beech is a key topic for Europe as it is one of the most important and abundant broad-leaf species. Physical, mechanical and esthetical features influence both the value and the usage of this wood in each commercial product. In this sense, the comprehension of the surface color modifications induced by solar irradiation is of crucial importance to define the commercial value of the beech wood.Starting from these general remarks, the aim of this work is to study the surface modifications on beech wood with and without red heartwood by different spectroscopic techniques and to obtain a modeling of the changes validated by rigorous statistical and chemometric methods together with principal component analysis.The artificial photo-irradiation of the wood samples was performed in a Solar Box. Reflectance spectrophotometry, Fourier Transform Infrared spectroscopy and hyperspectral imaging were used to assess artificial sunlight influence. The experimental data were statistically treated in order to evaluate their significance.Color monitoring allowed to find that the chromatic coordinates (L*a*b*) in normal wood and in red heartwood tended to similar values after 504 h of photo-irradiation.Fourier Transform Infrared spectroscopy showed the rate of photo-degradation of wood surface due to lignin oxidation and the statistical analysis allowed to demonstrate that red heart and normal wood have the same behavior.Concerning hyperspectral imaging (HSI), the detected spectral features were correlated to color changes in the Visible–Near Infrared (VIS–NIR) range (400–1000 nm) and to the variations of cellulose and lignin during accelerated aging in the Short-Wave Infrared (SWIR) range (1000–2500 nm).The most important result is that a correlation, validated by statistical analysis, of the color changes may be derived with the photo-degradation of wood components obtained by spectral analysis. This fact suggests the possibility to choose the reflectance spectrophotometry as a non-invasive, simple standard method to monitor the state of preservation of the wood surfaces.
Keywords: Fagus sylvatica L.; Red heartwood; Wood color; Reflectance spectrophotometry; Fourier Transform Infrared spectroscopy; Hyperspectral imaging;
Flame-retardant mechanism of a novel polymeric intumescent flame retardant containing caged bicyclic phosphate for polypropylene by Xuejun Lai; Shuang Tang; Hongqiang Li; Xingrong Zeng (22-31).
A novel polymeric intumescent flame retardant, named poly(ethanediamine−1,3,5-triazine-o-bicyclic pentaerythritol phosphate) (PETBP), was synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), solid-state 13C nuclear magnetic resonance (13C NMR), 31P NMR and elemental analysis (EA). The effects of PETBP on the flame retardancy and thermostability of polypropylene (PP) were investigated by limiting oxygen index (LOI), vertical burning test (UL-94V), cone calorimetric test (CCT), thermogravimetric analysis (TGA) and TG-FTIR, respectively. The results showed that PETBP could significantly improve the flame retardancy and thermostability of PP. When the content of PETBP was 25.0 wt%, the PP/PETBP mixture could achieve a LOI value of 29.5% and a UL-94 V-0 rating, and its peak heat release rate (PHRR), total heat release (THR), average mass loss rate (av-MLR), smoke production rate (SPR) and total smoke production (TSP) were considerably decreased. The flame-retardant mechanism of PETBP was investigated by TGA, FTIR, TG-FTIR and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDXS). The results revealed that during the combustion PETBP could quench the free radicals of PP chain scission, and form a continuous and compact intumescent char on the substrate, thus effectively retard the degradation and combustion of PP.
Keywords: Polymeric intumescent flame retardant; Polypropylene; Caged bicyclic phosphate; Single-component; Flame-retardant mechanism;
Chemiluminescence studies on comparison of antioxidant effectiveness on multiextruded polyethylenes by Karmele del Teso Sánchez; Norman S. Allen; Christopher M. Liauw; Fernando Catalina; Teresa Corrales; Michelle Edge (32-39).
Several polyethylene resins; high density polyethylene (Ph-HDPE, Phillips metal oxide catalyst) and linear low density polyethytlenes (LLDPE, formed using Ziegler–Natta catalyst and metallocene catalyst technology, m-LLDPE) were used in order to acquire an insight in to the effect of different polymerization catalyst systems on the melt stabilization performance of single AO. Chemiluminescence (CL) and melt flow rate (MFR) were used to analyze the degradation as a function of the number of passes through a twin-screw extruder. A good correlation was obtained, and the additives resulting with the best melt flow stability in the polymer were the same as those that promote the best CL results.
Keywords: Chemiluminescence; Degradation; Polyethylene; Melt flow index;
A SEM study on the use of epoxy functional vegetable oil and reactive UV-absorber as UV-protecting pretreatment for wood by S.K. Olsson; H. Matsunaga; Y. Kataoka; M. Johansson; J. Matsumura; M. Westin; E. Östmark (40-45).
The present study investigates the ageing performance of a UV protective system for wood, comprising the reactive UV absorber 2-hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP) and epoxy functional vegetable oils (linseed and soybean oil). Scots pine samples of radial or cross-sectional surfaces were treated using a combination of the two components, or using only one of the oils. The treated samples were then aged in a Weather-Ometer for 2 × 60 h and analysed using VPSEM to follow the degradation of the wood substrate in the exact same spot before, during and after ageing. The results of the radial surfaces show slightly less degradation of samples treated with a combination of HEPBP and oil, and for the cross-sectional surfaces an even stronger protective effect is visible. For samples treated with only one of the two oils, no improvement was detectable. The radial surfaces were also analysed using FTIR where the results indicate presence of the protective treatment even after 120 h of exposure. Overall the combined pretreatment of HEPBP and epoxy functional linseed oil was concluded to have a photostabilising effect of the wood substrate.
Keywords: UV-absorber; Epoxy functional vegetable oil; Linseed oil; 2-Hydroxy-4(2,3-epoxypropoxy)-benzophenone (HEPBP);
Heat stabilising flexible PVC with layered double hydroxide derivatives by F.J.W.J. (Johan) Labuschagne; Dan Matlhomola Molefe; Walter W. Focke; Isbé van der Westhuizen; Harry Charles Wright; Mikhail David Royeppen (46-54).
The layered double hydroxide ([Mg0.667Al0.333(OH)2](CO3)0.167·mH2O) (LDH) has found application as a heat stabiliser for PVC. Derivatives of this compound were synthesised using a hydrothermal method. Emulsion grade PVC was plasticised with 100 phr diisononyl phthalate and stabilised with 30 phr of the LDH filler additives. Heat stabilities were determined at 200 °C. The dynamic heat stability tests were performed on the plastisols using the torque rheometer method. Static heat stability was evaluated on the fused compounds. It was evaluated from discoloration profiles of strips exposed for various lengths of time to heat in a Metrastat oven. The time dependence of hydrogen chloride evolution was followed with a Metrohm Thermomat instrument. The conventional LDH provided the best dynamic heat stability. However, partial replacement of the magnesium with copper significantly delayed the release of volatile HCl. If instead the replacement was done using zinc, better colour retention was achieved.
Keywords: Layered double hydroxide; Poly(vinyl chloride); Heat stabiliser; Thermal analysis;
The thermo-oxidation of isoprene containing copolymers of isobutylene: Activation energies and reactions from room temperature to 100 °C by Richard J. Pazur; Ivan Petrov (55-65).
The activation energies of two poly(isobutylene-co-isoprene) (IIR) copolymers containing 0.9 and 1.85 mol% isoprene were determined under thermo-oxidation conditions from ambient to 100 °C. Transmission Fourier Transform Infrared (FTIR) spectroscopy was used to follow the functional group development. Ketone generation was the dominant oxidative product above 70 °C whereas below this temperature, carboxylic acid formation was prevalent. Non-Arrhenius kinetic behavior was observed due to curvature taking place near 70 °C. The estimated activation energies for the high and low temperature degradation processes were 85–87 kJ/mol and 49 kJ/mol. Test results were interpreted in terms of two competing thermo-oxidative zones, isobutylene and isoprene, the latter operating at low temperatures as shown by isoprene depletion and chain scission reactions. A set of thermo-oxidative reactions for IIR copolymers is proposed comprising allylic and addition reactions at the isoprene unit.
Keywords: Butyl rubber; Thermo-oxidation; Activation energy; Arrhenius; FTIR; NMR;
Probing molecular ordering in the HCl-doped polyaniline with bulk and nanofiber morphology by their thermal behavior by Marcelo M. Nobrega; Celly M.S. Izumi; Marcia L.A. Temperini (66-71).
Conducting polymers are an amazing class of materials, which provide new approaches in material design. The study of the thermal stability of polyaniline (PANI) is of great importance since heating is the initial step in several polymer processing methods. Concerning the studies of PANI's thermally induced structural changes, it has been observed that structural changes lead to the formation of phenazine-like structures or induce the thermal dedoping depending on the morphology and doping level, however, it was not completely clear the reason why some polymers presented the dedoping and others the cross-linking reaction after heating. In this paper, the influence of the morphology (bulk or nanofibers) on the thermal behavior of doped PANI (PANI-ES) have been investigated using the mass spectrometry-coupled thermogravimetric analysis, Raman spectroscopy and scanning electron microscopy. Our data have shown that nanofibers of PANI-ES are resistant to the thermal induced dedoping process and the major structural change have been the formation of high amount of phenazine-like segments, while for bulk PANI-ES, the dedoping process has been favored. The amount of phenazine-like segments induced by heat was dependent not only the presence of the polaronic segments but also on the molecular ordering.
Keywords: Polyaniline; Thermal behavior; Structural changes; Molecular ordering; Raman spectroscopy; Cross-linking;
Reprocessing of wood flour reinforced polypropylene composites: Impact of particle size and coupling agent on composite and particle properties by L. Soccalingame; A. Bourmaud; D. Perrin; J.-C. Bénézet; A. Bergeret (72-85).
This work aims to understand the degradation induced by multiple injection molding cycles on numerous properties of wood flour reinforced polypropylene (PP) composites. The influence of the initial wood particle size was studied as well as the influence of the addition of polypropylene grafted with maleic anhydride (PPgma) as a coupling agent at a given rate. Biocomposite compounds (20wt% of wood flour) are produced by twin-screw extrusion. Then, multiple injection and grinding cycles were performed (up to 7 cycles) to obtain normalized samples. The evolution of the wood flour particle characteristics is first assessed by SEM observation, size measurements and nanoindentation experiments. Then, the evolution of the PP matrix microstructure is determined by SEC tests (average molecular weight measurements), rheometer tests and DSC (polymer crystallinity). Finally, material mechanical properties are measured at a macro-scale thanks to tensile tests. Our experimental results show that the composite mechanical properties remain quite stable after 7 processing cycles despite wood flour degradation and PP degradation.
Keywords: Recycling; Coupling agent; Nanoindentation; Spruce wood flour; Polypropylene; Composite;
Rigid and steric hindering bisphosphate flame retardants for polycarbonate by Kai Huang; Qiang Yao (86-94).
Rigid steric hindering spiro-bisphosphates (PDMPDP and PDBPDP) were synthesized from spiro-pentaerythritol chlorophosphate and 2,6-dimethylphenol and o-tert-butylphenol respectively in order to investigate the effect of steric hindering groups on the flame retardant mechanism of bisphosphates and the effect of rigid spiro-pentaerythritol structure on the heat distortion temperature (HDT) of polycarbonate. A comparison of the steric hindering spiro-bisphosphates with the simplest phenyl spiro-bisphosphate (PDPDP) and commercial resorcinol bis(diphenyl phosphate) (RDP) on the flame retardancy of polycarbonate reveals that the presence of a thermally stable steric hindering group not only changes the efficiency but also shifts the mode of flame retardancy. In spite of low phosphorus content, PDMPDP and RDP show the highest efficiency of flame retardancy toward polycarbonate as evidenced by UL-94 combustion results with RDP exhibiting the strongest vapor phase action, PDMPDP the second, and PDPDP the least as judged from the phosphorus distribution in the vapor and the condensed phase. This is parallel to the tendency of chemical interactions between polycarbonate and flame retardants with PDPDP demonstrating the greatest interaction as proven by TGA study in air. It is suggested that the charring process of PDPDP interferes with that of polycarbonate and leads to microporous char that is seen in SEM and partially responsible for the poor flame retardancy of PDPDP. Compared to PC/RDP, PC/PDMPDP has a high HDT value.
Keywords: Steric hindering phosphate; Spiro-bisphosphate; Flame retardant; Polycarbonate;
Special issue based on the Fire Retardant Technologies 2014 conference held at University of Central Lancashire, Preston, UK April 2014 by Baljinder Kandola; T. Richard Hull; John Liggat; Anna A. Stec (95).
Recent advances for microencapsulation of flame retardant by Bibo Wang; Haibo Sheng; Yongqian Shi; Weizhao Hu; Ningning Hong; Wenru Zeng; Hua Ge; Xiaojuan Yu; Lei Song; Yuan Hu (96-109).
In this paper microencapsulation of magnesium hydroxide, red phosphorus, inorganic phosphorus and organic flame retardants have been reviewed. The effects of different shell materials on the properties of microencapsulated flame retardant and composites have been carefully and thoroughly discussed. It has been demonstrated that microencapsulation provide better water resistance, flame retardancy, compatibility and higher pyrolysis temperature, etc. With proper shell material, the microcapsules not only possess better properties, but also can be used in more rigorous situation.
Keywords: Microencapsulation; Flame retardant; Microcapsule; Shell material; Composites;
Thermal degradation of DNA, an all-in-one natural intumescent flame retardant by Jenny Alongi; Alessandro Di Blasio; John Milnes; Giulio Malucelli; Serge Bourbigot; Baljinder Kandola; Giovanni Camino (110-118).
Very recently, deoxyribonucleic acid (DNA) has proven to be an efficient renewable, natural flame suppressant and retardant, due to its intrinsic intumescent features. In our previous work, we have explored its flame retardant activity by applying as a surface coating on cotton fabrics and observed that on exposure to heat, the DNA was able to form a foamed char on the surface of the fabric. These remarkable results have stimulated the present study on in-depth understanding of mechanism of thermal degradation of DNA. A number of characterization techniques have been exploited to investigate DNA decomposition, namely: thermogravimetry coupled with infrared spectroscopy or combined with differential thermal analysis, pyrolysis-combustion flow calorimetry and analysis of degradation residues. A scheme of DNA degradation mechanism is proposed to account for the results of the study.
Keywords: Thermal degradation; TGA; TGA-IR; Pyrolysis-Combustion Flow Calorimeter; Intumescent flame retardants;
An overview of some recent advances in DOPO-derivatives: Chemistry and flame retardant applications by Khalifah A. Salmeia; Sabyasachi Gaan (119-134).
Owing to the toxicity and environmental concerns of halogen-containing flame retardants, phosphorus-containing flame retardants have attracted much attention as ecofriendly substitutes. Synthesis of organophosphorus compounds based on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its application as flame retardant have created much attention in the flame retardant community. Various chemical reactions and synthetic approaches are followed to develop numerous derivatives of DOPO. This review focuses on the recent advances in DOPO chemistry, classifying its derivatives based on the chemical reactions and functional groups. The reaction mechanisms of each specific reaction for DOPO derivatization are discussed in detail. Additionally some characteristic applications of these DOPO-derivatives with important flammability performance are also reported in this short review.
Keywords: 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO); Phosphorus-containing compounds; Reaction mechanism; DOPO-derivatives; Flame retardants;
Chemical modification of lignin by phosphorus molecules to improve the fire behavior of polybutylene succinate by L. Ferry; G. Dorez; A. Taguet; B. Otazaghine; J.M. Lopez-Cuesta (135-143).
Lignin was used as flame retardant for polybutylene succinate (PBS) biopolyester. Lignin was first demonstrated to weakly contribute to material flammability due to a high charring ability and a low heat release when burning. Alkali lignin was proved to be more interesting than organosolv lignin due to the release of sulfur dioxide during decomposition. When incorporated at a 20%wt loading in PBS, alkali lignin significantly reduces pHRR and promotes a thick charring behavior. Alkali lignin was successfully surface modified by grafting molecular or macromolecular phosphorous compounds. When blended with PBS, modified lignin was highlighted to further increase the barrier effect. Char promotion is accelerated and the resulting charred layer exhibits a higher cohesivity. Modified lignin appears as an interesting biobased flame retardant component.
Keywords: Lignin; Polybutylene succinate; Flame retardancy; Thermal degradation; Grafting; Phosphorus;
The thermo-oxidative degradation of poly(4-methylstyrene) and its relationship to flammability by S. McCreath; J.P. Lewicki; J.J. Liggat; C. Lithgow; L. McCulloch; K. Miller; A. Witkowski (144-153).
Polystyrene and poly(4-methylstyrene) have very similar chemical structures with the only differences being the para methyl group of poly(4-methylstyrene). This methyl group is susceptible to oxidation at elevated temperatures. Here we demonstrate that it is possible to introduce oxidative cross-links to poly(4-methylstyrene), via the para methyl group, by thermal oxidative treatment at 230 °C, 250 °C and 270 °C in the absence of catalyst, leading to a material with markedly modified thermal degradation chemistry. Thermal gravimetric analysis and differential scanning calorimetry were used to characterise and compare untreated and post-oxidised materials and established that as the temperature of pre-treatment was increased, the subsequent thermal stability of the material increased. FTIR, NMR and microanalysis indicated that after the thermal oxidative pre-treatment ether cross-links are present alongside new oxygen containing functional groups such as aldehydes, carboxylic acids and hydroxyl groups. Finally, data obtained from pyrolysis combustion flow calorimetry confirmed that as the number of oxidative cross-links increase, a reduction in the polymer's flammability as assessed by heat release data is observed.
Keywords: Thermo-oxidation; Thermogravimetry; Pyrolysis combustion flow-calorimetry; Cross-linking;
Blends of unsaturated polyester and phenolic resins for application as fire-resistant matrices in fibre-reinforced composites. Part 2: Effects of resin structure, compatibility and composition on fire performance by Baljinder K. Kandola; Latha Krishnan; Dario Deli; John R. Ebdon (154-167).
The effects of co-curing blends of an unsaturated polyester (UP) with inherently fire-retardant and char-forming phenolic resoles (PH) on the thermal stability and fire retardancy of the resulting resins have been investigated. To overcome the challenge of UP/PH incompatibility, arising from their different chemical structures and curing mechanisms (radical vs. condensation), different phenolic resoles have been used: ethanol-soluble, epoxy-functionalized, and allyl-functionalized. A traditional water-based resole has also been used to give a reference non-compatible system. In Part 1 of this series of publications it was shown that the compatibility of the two resins increases with functionalization; the allyl-functionalized resole showing the best compatibility with UP. Limiting oxygen index measurements and cone calorimetry have shown that fire performance of the functionalized PH resins and their blends with UP is worse than that from the unfunctionalized PH resin, but still significantly better than that of the UP. To understand this behaviour, thermal analyses coupled with infrared spectroscopy of volatile degradation products have been used on all resins and their blends, based on which, mechanisms of their decomposition and interactions are proposed, and the effects of these on flammability are discussed.
Keywords: Unsaturated polyester; Phenolic resole; Blend; Fire performance; Thermal stability; Cone calorimetry;
Decomposition mechanism of fire retarded ethylene vinyl acetate elastomer (EVA) containing aluminum trihydroxide and melamine by Carmen Hoffendahl; Sophie Duquesne; Gaëlle Fontaine; Frank Taschner; Martin Mezger; Serge Bourbigot (168-179).
The objective of this study is to evaluate the influence of aluminum trihydroxide (ATH) and melamine (MEL) mixture on the flame retardant and smoke release properties of ethylene vinyl acetate (vinyl acetate content of 60 wt%, EVA). The fire retardant properties were evaluated by mass loss calorimetry (MLC), limiting oxygen index (LOI) and UL-94. A home-made smoke test was developed to evaluate the smoke release of the material in a given scenario. It was found that the addition of ATH to EVA leads to improved fire retardant properties and reduced smoke release. Partial substitution of ATH by MEL at different ratios resulted in better results in MLC for a ratio of ATH:MEL of 5:1 and 10:1. Moreover, a lower quantity of smoke was released for EVA–ATH–MEL materials during material decomposition.A ratio of ATH:MEL of 5:1 was found to be the most promising. It was also shown that EVA–ATH–MEL ignited at shorter time in MLC test but longer ignition time in smoke test in comparison to EVA–ATH which is due to different test conditions. To understand the role of melamine on material properties, the degradation pathway of EVA–ATH–MEL was analyzed in details. The dispersion of the additives was examined by scanning electron microscopy (SEM) showing that all additives are homogenously dispersed in the matrix. In the next step the pyrolytic decomposition was investigated using thermogravimetric analysis (TGA) and pyrolysis-gas chromatography–mass spectrometry (py-GCMS). The decomposition of EVA–ATH–MEL was then analyzed in the gas phase using MLC coupled with a Fourier transform infrared spectrometer (MLC–FTIR) and in the condensed phase using solid state nuclear magnetic resonance (NMR) of 13C and 27Al. It was concluded that the additives protected the EVA both by a gas and condensed phase mechanism. The endothermic decomposition of ATH has a cooling effect and dilutes the fuel through release of water in the gas phase. Moreover, in the condensed phase, EVA–ATH–MEL is protected through formation of a char acting as barrier slowing down heat and mass transfer compared to EVA–ATH. Ignition at shorter times of EVA–ATH–MEL in comparison to EVA–ATH was found to be due to higher amount of flammable gases in the gas phase before ignition.
Keywords: Ethylene vinyl acetate; Elastomer; Fire retardancy; Smoke production; Aluminum trihydroxide; Melamine;
Flame retardant flexible polyurethane foams from novel DOPO-phosphonamidate additives by Sabyasachi Gaan; Shuyu Liang; Henri Mispreuve; Heribert Perler; Reinold Naescher; Matthias Neisius (180-188).
In this work we report synthesis and flame retardant application of novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based phosphonamidates. Two mono and one bis DOPO-phosphonamidates were synthesized and incorporated in polyether based polyurethane (PU) manufacturing process. For the comparison of fire performance of these DOPO-phosphonamidates, we have chosen commercially available flame retardants (TCPP, DOPO and Exolit® OP 560) commonly used in flexible PU foam manufacturing. UL94 HBF fire results of various PU foam formulations indicate that DOPO-phosphonamidates exhibit superior fire performance as compared to the commercial flame retardants. 6,6′-(ethane-1,2-diylbis-(azanediyl)-bis-(6H-dibenzo[c,e][1,2]-oxaphosphine-6-oxide (EDAB-DOPO))/foam formulations exhibit the best fire performance as compared to other DOPO-phosphonamidate/foam formulations. A concentration of only 5% EDAB-DOPO on wt. of polyol is needed to achieve a HF1 rating. Thermal decomposition studies of the DOPO-phosphonamidate/foam formulations indicate their limited condensed phase interaction. In TGA experiments, a very small residue (<5%) was observed at 800 °C for all PU formulations. Additionally EDAB-DOPO showed evidence of intermediate condensed phase interaction in the first stage of PU foam decomposition. Direct insertion probe (DIP) – MS studies indicate that mono DOPO-phosphonamidates volatilize primarily in the first stage of thermal decomposition of PU foams whereas the EDAB-DOPO, being thermally more stable is only detected in gas phase in the second stage. Like in case of TCPP/PU foam formulation, the increase in the CO/CO2 ratio in the cone calorimeter experiments for the DOPO-phosphonamidate/foam formulation further proves the gas phase activity (flame inhibition) of these DOPO-phosphonamidates. EDAB-DOPO being thermally more stable seems to offer more sustained gas phase activity during the entire burning stage of PU foams in cone calorimeter experiments. Higher thermal stability of EDAB-DOPO may explain its superior flame retardant efficacy among all the DOPO-phosphonamidates investigated in this study.
Keywords: Flexible polyurethane foam; Flame retardant; DOPO-phosphonamidate; PO-species analysis; Burning test;
Layer by layer assembly of flame retardant thin films on closed cell PET foams: Efficiency of ammonium polyphosphate versus DNA by Federico Carosio; Fabio Cuttica; Alessandro Di Blasio; Jenny Alongi; Giulio Malucelli (189-196).
The present work aims to investigate the layer by layer deposition of flame retardant thin coatings on closed cell polyethylene terephthalate foams. To this aim, two coating architectures have been selected in order to evaluate the efficiency of ammonium polyphosphate (APP) versus the freshly proved flame retardant deoxyribonucleic acid (DNA). Both the selected architectures were able to homogeneously coat the external surface of the foams; APP-based coatings yielded average thicknesses around 450 nm while DNA based counterparts reached 340 nm. Flammability and cone calorimetry tests clearly demonstrated the superior performances of APP-based coatings. Indeed, only these latter were capable of suppressing the melt dripping behavior typical of PET and reducing the heat release rate peak by 25%.
Keywords: PET foams; Layer by layer; Ammonium polyphosphate; Deoxyribonucleic acid; Flame retardancy; Flammability;
Influence of the composition of PMMA nanocomposites on gaseous effluents emitted during combustion by Carine Chivas-Joly; Claire Longuet; Charles Motzkus; José-Marie Lopez-Cuesta (197-207).
This paper focuses on the nature of thermal degradation products formed by combustion of various PMMA nanocomposites and on the kinetics of emission of gases emitted during combustion. Compositions of two kinds of nanosilica and nanoalumina and their combinations with Ammonium PolyPhosphate (APP) in PMMA were prepared. Their thermal degradation was carried out using TGA coupled with FTIR and cone calorimeter. For the compositions of nanooxides, it appears that the kinetics of emission of gases is significantly influenced by the nature of oxide and by the surface treatment, but mainly for silica. Octylsilane modified silica combined with APP leads to an outstanding fire behaviour, due to the formation of a very cohesive and expanded layer containing silicon pyrophosphate, but at the expense of a higher CO emission and a measurable emission of HCN. Even if the presence of fire retardant (APP) and the incorporation of nanosilica with a surface treatment reduce the flammability, the high value of the CO yield could lead to the conclusion that the combination could improve toxicity. But, the nanocomposite based on silica surface treatment coupled with APP, induce a delay of the CO yield emission, which could allow people to evacuate buildings or houses in case of fire.
Keywords: Nanoparticles; Cone calorimeter; FTIR; Emission yields; Kinetics of gases;
Development of an anaerobic pyrolysis model for fire retardant cable sheathing materials by Artur Witkowski; Bertrand Girardin; Michael Försth; Fiona Hewitt; Gaëlle Fontaine; Sophie Duquesne; Serge Bourbigot; T. Richard Hull (208-217).
Wire and cable coverings are potentially a major cause of fire in buildings and other installations. As they need to breach fire walls and are frequently located in vertical ducting, they have significant potential to increase the fire hazard. It is therefore important to understand the ignition and burning characteristics of cables by developing a model capable of predicting their burning behaviour for a range of scenarios. The fire performance of electrical cables is usually dominated by the fire performance of the sheathing materials. The complexity of the problem increases when cable sheathing incorporates fire retardants. One-dimensional pyrolysis models have been constructed for cable sheathing materials, based on milligram-scale and bench-scale test data by comparing the performance of three different software tools (ThermaKin, Comsol Multiphysics and FDS, version 6.0.1). Thermogravimetric analysis and differential scanning calorimetry were conducted on powdered cable coatings to determine the thermal degradation mechanism, the enthalpy of decomposition reactions, and the heat capacities of all apparent species. The emissivity and the in-depth absorption coefficient were determined using reflectance and transmittance measurements, with dispersive and non-dispersive spectrometers and integrating spheres. Bench-scale tests were conducted with a mass loss calorimeter flushed with nitrogen on samples in a horizontal orientation, for comparison with the pyrolysis model of non-flaming decomposition at an external heat flux of 50 kW m−2. The parameters determined through analysis of the milligram-scale data were used to construct a pyrolysis model that predicted the total mass loss from calorimeter tests in anaerobic conditions. A condensed phase pyrolysis model that accurately predicts in-depth temperature profiles of a solid fuel, and the mass flux of volatiles evolved during degradation of the fuel, is an essential component of a comprehensive fire model, which when coupled to a computational fluid dynamics code can be used to predict the burning processes in a fire scenario. Pyrolysis models vary considerably in complexity based on the assumptions incorporated into the development of the model.
Keywords: Pyrolysis; Thermal decomposition kinetics; Thermophysical properties; Polymer cable; Modelling; Fire retardant;