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Three different accelerated ageing scenarios were applied on flame retarded polylactic acid (FR-PLA). The influence of (i) Temperature and UV-light exposure (T/UV), (ii) Temperature and relative humidity exposure (T/RH) and (iii) combined Temperature, UV-light and relative humidity (T/UV/RH) exposure on (i) the morphology, (ii) the physico-chemical properties and (iii) the fire performances of FR-PLA were evaluated. The influence of FR fillers (melamine, ammonium polyphosphate and organomodified montmorillonite) as well as the associated mechanisms of degradation (i.e. photo-degradation under T/UV, hydrolysis under T/RH and a combination of both phenomena under T/UV/RH) were explained. The flame retardant properties of FR-PLA before and after ageing were compared using Limiting Oxygen Index (LOI) and Mass Loss Calorimetry (MLC). It was reported that FR-PLA aged under T/UV/RH conditions is more degraded compared to FR-PLA exposed to T/RH or T/UV. Surprisingly, the FR properties are enhanced after ageing, even if the degradation of the samples is observed. [ABSTRACT FROM AUTHOR]

• Model phosphorous flame retardants with various oxidation levels and boiling points. • Investigation of their flame retardant effects when incorporated in polyurethane and polyisocyanurate rigid foams. • Systematic characterization study of the condense phase. • Determination of the dominant mechanism of action for each phosphorus flame retardant. This study investigates different types of model phosphorous compounds for flame retardancy purposes to find new FR structures to flame retard rigid polyisocyanurate (PIR) and/or polyurethane (PUR) foams. Triethylphosphate (TEPate) has been taken as a reference since it is already known to enter into the composition of some FR systems for PIR or PUR foams. Commercially available phosphate, phosphonate, phosphite and phosphine oxide were chosen. All the foam systems were characterized using TGA analysis, rheology tests, and mass loss cone tests, and analyzed using solid state NMR and chemical analysis. DEPonate shows the best efficiency for improving the FR properties of PIR and PUR foam. For the other FRs, the effect on the fire behavior is less relevant especially for PUR foams. This behavior was explained by the fact that even if the FRs slightly decrease the pHRR, the THR or the flaming time, smoke production is usually strongly increased. The systematic study of the condensed phase demonstrates that even if a charring effect is induced by the FR, the effect is not strong enough to improve the FR properties of the material. DEPonate have the least developed char but the best FR properties in PIR and PUR foam, demonstrating that the gas phase effect is more predominant than the condense phase effect. [ABSTRACT FROM AUTHOR]

Effect of accelerated ageing on neat and flame retarded (FR) polylactide (PLA) has been investigated. The influence of temperature and relative humidity on (i) the visual aspect, (ii) the fire performances, (iii) the molecular mass and (iv) the thermal properties of the formulations has been evaluated. The flame retardant (FR) properties of samples before and after ageing were compared using Limiting Oxygen Index (LOI) and Mass Loss Calorimetry (MLC). It was reported that degradation of PLA, mainly driven by hydrolysis phenomenon, is accelerated in presence of FR fillers (melamine and ammonium polyphosphate). This is even more pronounced when an organomodified montmorillonite is added. However the FR properties are enhanced after ageing due to the physicochemical of the flame retarded materials (e.g. migration of the flame retardants, decrease of the molecular mass…). [ABSTRACT FROM AUTHOR]

A transparent fire protective sol-gel coating deposited on wood has been evaluated using different fire tests, such as mass loss cone, mini single burning item and furnace tests. The heat release rate and total heat release during combustion, but also the flame spread behavior and the thermal protection performances of the coatings have been studied. Two processes to apply the sol-gel coating on wood have been assessed to show the thickness dependence of the fire performance. When deposited as a thick coating (800 μm thick) on wood, the sol-gel coating lowers the total heat release, decreases the flame spread and greatly improves the thermal protection of the substrate. • Formulation of a flame retardant sol-gel coating. • Thick transparent sol-gel coating for wood panels. • Reduction of the flame spread. • Improved thermal properties. [ABSTRACT FROM AUTHOR]

Abstract: Layered double hydroxides (LDH) are a class of readily synthesizable layered crystals that can be used as an alternative to the commonly used silicate crystals for the preparation of polymeric nanocomposites. In this work layered double hydroxide/polyamide 6 nanocomposites (LDH/PA6) were prepared from organo-modified LDH by melt processing. The anionic exchange capacity of LDH was varied in order to investigate its influence on the degree of exfoliation. LDH were dispersed by a twin screw micro-extruder at a variety of processing conditions. The nanocomposites were characterized by wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), transmission electron microscopy, dynamic scanning calorimetry, and thermogravimetric analysis. It was found that exfoliated nanocomposites were successfully prepared by melt processing with a low exchange capacity LDH, whereas residue tactoids were observed with a high exchange capacity LDH. Shear, together with the exchange capacity, seems to be the key factor for the delamination in LDH/PA6. No major change in the crystalline phase or in the rate of crystallization was observed in the nanocomposite as compared to the neat polymer. A reduction in the onset of thermal decomposition temperature was observed in PA6/LDH compared to neat PA6, likely due to a nucleophilic attack mechanism. The properties of this nanocomposite system are discussed with connections to the current understanding within the broader nanocomposite field. [Copyright &y& Elsevier]

• Self-stratification process allows the formation of multifunctional coatings by one-step application. • The main parameters driving stratification are investigated and elucidated. • For the first time, bio-based epoxy resins are used to design effective self-stratifying coatings. • Cryo-Scanning Electron Microscopy was used to understand the in-situ self-stratification mechanism. Self-stratification is an innovative one-step process used to design multi-functional coatings gathering simultaneously in a one-pot formulation the primer, the intermediate layer and the top coat properties. Many self-stratifying coatings contain oil-based epoxy resins but the literature is scarce in the development of "greener" solutions. In this work, silicone resins and bio-based epoxy resins were dissolved in various solvent blends, applied on a composite substrate and cured under different conditions to obtain stratified coatings. To reach a perfect stratification, the influence of various parameters including (i) the surface tension and the polarity of the resins, (ii) the solvents volatility, (iii) the curing temperature and (iv) the reactivity of the epoxy/amine reaction was studied by a systematic approach. In accordance with the literature, it was demonstrated that a large difference in surface energy and polarity favors resins separation. The volatility of the solvent blend was also shown to be a key factor in the stratification process. However, the predominant parameter, rarely taken into account, is the curing temperature, which impacts the cross-linking reaction of the epoxy resin. The increase in molecular weight (MW) of epoxy resins due to the cross-linking reaction favors the incompatibility between resins by increasing the difference in MW between epoxy and silicone resins. Thus, optimization of process conditions allowed the design of perfectly stratified bio-based epoxy/silicone coatings. The mechanism of film stratification was also elucidated thanks to in-situ analyses. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of novel hybrid poly(lactic acid) by use of a titanium oxo-cluster, acting both as a catalyst and crosslinking agent of the polymer matrix. The already reported oxo-cluster Ti 16 O 16 (OEt) 32 ([Ti] 16) was synthesized and screened at the lab-scale as catalyst for the bulk polymerization of l -lactide (l -LA). [Ti] 16 was found to be highly active for this reaction as up to 90% conversion in 30 min was obtained, affording PLLAs with M n up to 65 000 g·mol−1 and relatively narrow dispersities (1.2–1.6). These polymerization reactions were further transposed to reactive extrusion process in which [Ti] 16 oxo-cluster kept its high activity, affording hybrid-PLLA materials with M n close to 58 000 g·mol−1 (some PLLAs could not be dissolved). Electronic micro-probe analysis of the resulting hybrid materials confirmed that the titanium oxo-cluster was well dispersed all over the PLLA matrix. Finally, it was shown that the hybrid PLLA containing [Ti] 16 display superior dimensional stability under heat than commercial PLLA of same molar mass. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the reaction to fire of thermoplastic polyurethane (TPU) containing polyhedral oligomeric silsesquioxanes (or POSSs) was investigated by mass loss calorimetry. This composite exhibits a large reduction of peak of heat release rate (PHRR) compared to virgin TPU. The protection occurs via an intumescent mechanism. Mechanism of protection is examined in chemical and physical ways. Solid state NMR of carbon and silicon on heat-treated materials reveals that there is no significant chemical interaction between TPU and POSS. Nevertheless the intumescent char is characterized as ceramified char made of silicon network in a polyaromatic structure. The expansion occurs because of the partial volatilization of the organic part of POSS and because of the evolving degrading products of TPU. The formation of this intumescent structure makes an efficient insulating material at the surface of the substrate limiting heat and mass transfer and then decreasing heat release rate. [Copyright &y& Elsevier]

A small-scale single burning item test has been developed to allow quicker, easier and less costly development studies of building materials presenting high performance. The test is fully described including the dimensions of the equipment, the procedure used to perform the test, but also the methodology used for the calibration of the heat release rate (HRR) and smoke production. To study the efficiency of the test, different rigid polyurethane and rigid polyisocyanurate foams, with and without flame retardants, are used as case studies and their fire behavior evaluated. The small-scale single burning item test allowed discriminating the different foams in terms of HRR and flame spread, but also in terms of FIGRA and SMOGRA index. It also permits an easy use of additional sensors (thermocouples) leading to a better understanding of the fire behavior. The results were compared to data obtained from the mass loss cone (ISO13927). The results in terms of HRR and smoke lead to similar conclusion but compared to mass loss cone, the small-scale single burning item test makes it possible to access the flame spread behavior of the materials, which is a crucial parameter and leads to an additional discrimination of the performance of the materials. [ABSTRACT FROM AUTHOR]

Abstract: In this work, the nanodispersion of organomodified montmorillonite (MMT) in polylactide (PLA), prepared by varying the processing conditions, is investigated by solid-state nuclear magnetic resonance (NMR). The method is based on T1 H (proton longitudinal relaxation time) measurement as a quantitative indicator of the dispersion. It permits extraction of two parameters: (i) f is the fraction of the potentially available clay surface, which has been transformed into polymer/clay interfaces and (ii) ε is a relative measure of the homogeneity of the dispersion of these actual polymer/clay interfaces. The NMR approach is consistent with transmission electron microscopy (TEM) results but, as a bonus, NMR allows providing of a quantitative view of the whole sample, while TEM is mainly qualitative and looks only at a tiny volume of the material. This critical advantage is used, for the first time, to quantitatively investigate the influence of the processing conditions on the nanomorphology of PLA/MMT nanocomposite. It is revealed that high mechanical energy for a short time (∼1min) followed by low shear stress for a reasonable residence time (∼5min) results in the delamination of the clay platelets (high f value) associated with a very high degree of homogeneity (ε=97%). Longer times and higher shear lead to the reagglomeration of the platelets. [Copyright &y& Elsevier]

Abstract: Layered double hydroxides/epoxy (LDHs/EP) nanocomposites were prepared from organo-modified LDHs, a diglycidyl ether of bisphenol A monomer (DGEBA) and amine curing agents. The organo-modified LDHs were obtained by ionic exchange of a magnesium–aluminum carbonate LDH in an acid medium. X-ray diffraction and transmission electron microscopy showed a dispersion of the layers at a nanometer scale, indicating the formation of LDH/EP nanocomposites. The thermal degradation and flame resistance properties of LDH/EP nanocomposites, montmorillonite–epoxy (MMT/EP) nanocomposites, LDH/EP microcomposites and aluminum hydroxide–epoxy microcomposites were compared by thermogravimetrical analyses, simultaneous thermal analyses, UL94 and cone calorimeter tests. Only LDH/EP nanocomposites showed self-extinguishing behavior in the horizontal UL94 test; LDH/EP microcomposites and MMT/EP nanocomposites samples burned completely showing that the unique flame resistance of LDH/EP nanocomposites is related to both the level of dispersion and the intrinsic properties of LDH clay. Furthermore, cone calorimeter revealed intumescent behavior for LDH/EP nanocomposites and a higher reduction in the peak heat release rate compared to MMT/EP nanocomposites. [Copyright &y& Elsevier]

Additive manufacturing is a powerful tool to design materials with original properties. An innovative design of poly (Ethylene Vinyl Acetate) (EVA) containing 30 wt.-% of Aluminum TriHydroxide (ATH) was reported in a previous paper and liquids (water or potassium carbonate aqueous solution) were incorporated in the 3D printed structure. These multi-materials showing interesting properties, but stability, control and processing of these liquid-containing systems were an issue due to porosity of the polymeric matrix. To overcome this issue, the use of hydrogels is considered in this study: being either solid or highly viscous, hydrogels can retain water in the design, despite the high porosity of the EVA/ATH matrix. In this paper, the liquid phase was substituted by flame retardant hydrogels (based on agar, alginate or poly (vinyl alcohol) - PVA), containing in particular vermiculite platelets and for the hydrogel based on alginate, K 2 CO 3 as flame retardant fillers. Excellent behavior under a 50 kW/m2 heat flux during a cone calorimeter test was obtained, with fast extinguishment of the flame and a low peak of Heat Release Rate (pHRR) and Total Heat Release (THR). The physical barrier formed by vermiculite platelets during the test, as well as the condensed phase mechanism of K 2 CO 3 were found to be responsible for these excellent results, as found by confocal microscopy observations, electron probe micro analysis and X-Ray diffraction experiments. Image 1 • New concept of flame retardant sandwich 3D printed materials. • Creation of biphasic material containing hydrogel. • Action in gas (K 2 CO 3) and condensed (clay and K 2 CO 3) phases. [ABSTRACT FROM AUTHOR]

Glass-fiber reinforced polyamide 66 is flame retarded with a mixture of melamine-poly(zinc phosphate), (Safire ® 400) and diethyl aluminium phosphinate. The performance of this synergistic combination of additives is multi-modal and a comprehensive investigation is undertaken to elucidate the underlying flame retardancy mechanism. The strategy was to characterize the different chemical species responsible for flame retardancy that are generated in gas and condensed phases under different fire scenarios. Following heat release rate (HRR) curve of flame retarded polyamide formulations obtained by mass loss calorimeter, samples in different stages of degradation are collected and investigated. Further flame retardants and formulations were degraded in tubular furnace whose temperature protocol relied on thermal degradation profile obtained from thermogravimetric analysis (TGA). In either case, species generated in condensed phase were studied by solid state nuclear magnetic resonance spectroscopy (magic angle spinning (MAS) NMR; 27 Al, 31 P and 13 C), Fourier transform Infra-red spectroscopy (FTIR), X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and optical microscopy, whereas TGA coupled FTIR, and pyrolysis gas chromatography mass spectrometry (Py/GC/MS) were utilised to investigate species released in gas phase. Flame retardancy mechanism is elaborated based on the identification of the chemical species in both gas and condensed phases and their specific contributing role. [ABSTRACT FROM AUTHOR]

Abstract: The obvious aspect of nanodispersion and its role when investigating fire retardancy is not often clearly commented upon in the literature. Polymer clay nanocomposites can exhibit different morphologies and these might have consequences for their fire behaviour. Using solid state NMR to quantify the nanodispersion of organoclay in polyamide-6 (PA-6), we have prepared by melt blending PA-6/clay nanocomposite exhibiting different nanomorphologies. NMR results are consistent with transmission electron microscopy (TEM) images but the advantage of NMR is that it is representative of the whole sample and provides a precise quantification. PA-6 nanocomposites exhibit significant reduction of PHRR but the nanomorphology (exfoliation, intercalation and presence of tactoids) does not play any significant role. In other words, we have clearly shown that if nanodispersion is achieved, polymer/clay nanocomposite should exhibit fire retardant properties. [Copyright &y& Elsevier]

Abstract: As the nanocomposite properties dramatically depend on the dispersion state of the filler in the matrix, it is essential to develop technical methods to characterise the nanodispersion both qualitatively and quantitatively. In this study, complete characterisations of the nanodispersion of organomodified clays in polyamide 6, polypropylene and poly(butylene terephtalate) are presented and discussed using different analytical tools. All four characterisation methods have been evaluated experimentally. TEM has been used to qualitatively characterise the dispersion. As TEM picture might be not fully representative of the whole sample, many pictures have to be analysed to mirror the global repartition. XRD is particularly adapted to the study of intercalated morphology of nanocomposite since the distance between two platelets can be calculated but needs TEM to provide more complete conclusions. Melt rheology and solid-state NMR are bulk analyses. During the measurement the sample is representative of the material. Rheology is relatively simple to make measurements and to get semi-quantitative data. In connection with NMR, we can get quantitative measurements on the degree of nanodispersion in the nanocomposite. [Copyright &y& Elsevier]

Abstract: Flame retardant nanocomposites have attracted many research efforts because they combine the advantages of a conventional flame retardant polymer with that of polymer nanocomposite. However the properties obtained depend on the dispersion of the nanoparticles. In this study, three types of polymer flame retarded nanocomposites based on different matrices (polypropylene (PP), polybutadiene terephtalate (PBT) and polyamide 6 (PA6)) have been prepared by extrusion. In order to investigate the dispersion of nanoparticles in the polymer containing flame retardant, conventional methods used to characterise the morphology of composites have been applied to FR composites containing nanoclays. XRD, TEM and melt rheology give useful information to describe the dispersion of the nanofiller in the flame retarded nanocomposite. In the PA6-OP1311 (phosphorus based flame retardant) materials, the clay is well dispersed unlike in PBT and PP materials where microcomposites are obtained with some intercalation. The poor dispersion is also highlighted by NMR measurements but the presence of flame retardant particles interferes in the quantitative evaluation of nanoclay dispersion and underestimations are made. [Copyright &y& Elsevier]

This work investigates the melt-processing of styrene–acrylonitrile copolymer (SAN) with organo-modified montmorillonite (MMT) clays and the influence of the clay on mechanical properties and on fire performance of SAN. The nanodispersion of MMT is evaluated qualitatively by X-ray diffraction (XRD) and transmission electronic microscopy (TEM), and quantitatively by solid state nuclear magnetic resonance (NMR). SAN/MMT nanocomposites reveal an intermediate morphology, an intercalated structure with some exfoliation and with the presence of small tactoids, whatever the loading in MMT is. The polymer–clay interfacial area is estimated at 0.5 and the degree of homogeneity characterizing the distribution of MMT platelets is about 40%. The presence of clay in SAN-25 leads to a ‘filler effect’ increasing the stiffness but decreasing tensile strength of the nanocomposites. It also leads to a significant decrease of peak of heat release rate measured by mass loss calorimetry. [Copyright &y& Elsevier]

Nowadays, before setting up an industrial process, special attention has to be paid to its environmental footprint. This new way of thinking allows evaluating the hotspots so as to propose solutions to conceive more eco-friendly processes. Thus, the coating industry is increasingly preoccupied by the environmental impacts of newly designed paints. That is why innovation tries to take into consideration both the formulation composition and the application and drying methods. Following a Life Cycle Assessment (LCA) approach, the present study aims to compare the environmental impacts of self-stratifying coatings (with three process steps), either oil-based or bio-based, to those of an oil-based multilayered coating (with six process steps). The concept of the self-stratifying coating is to bring the primer, the intermediate and the top coat properties together in a one-pot formulation to produce a multi-functional coating through a less laborious process. The total environmental impact of each process can be characterized by four main categories of impacts: Climate Change Human Health (CCHH), Human Toxicity (HT), Climate Change Ecosystem (CCE) and Fossil Depletion (FD), which together represent approximately 86% of the global impact for each system. The results obtained show that the self-stratifying oil-based coating process is more energy efficient compared to the currently used multilayered oil-based coating process, with a 15% decrease of CCHH, HT and CCE indicators and a 14% decrease of FD indicator, corresponding to a 13.6% decrease of the total environmental impact. However, as this decrease was lower than expected, particular attention was then paid to the chemicals used (resins, solvents) and to the process conditions. The substitution of the oil-based epoxy resin by a bio-based one and the use of less harmful solvents allow reducing the total environmental impact by 32.4% compared to the multilayered oil-based system (with 30% decrease of CCHH indicator, 50% of HT indicator, 31% of CCE indicator and 34% of FD indicator). In a global way, electricity consumption control and the nature of chemicals used were reported to contribute in a significant way to the improvement of the process environmental impact. Image 1 • Comparison of the environmental impact of multilayered vs self-stratifying coatings. • Major contribution of energy consumption for all the studied processes. • Importance of the use of a bio-based resin and of greener solvents is highlighted. • Influence of the number of processing steps and of the drying conditions. [ABSTRACT FROM AUTHOR]