Copper(0)-mediated radical polymerisation in a self-generating biphasic system

Herein, we demonstrate the synthesis of well-defined poly(n-alkyl acrylate)s via copper(0)-mediated radical polymerisation in a self-generating biphasic system. During the polymerisation of n-butyl acrylate in DMSO, the polymer phase separates to yield a polymer-rich layer with very low copper content (ICP-MS analysis: 0.016 wt%). The poly(n-butyl acrylate) has been characterized by a range of techniques, including GPC, NMR and MALDI-TOF, to confirm both the controlled character of the polymerisation and the end group fidelity. Moreover, we have successfully chain extended poly(n-butyl acrylate) in this biphasic system several times with n-butyl acrylate to high conversion without intermediate purification steps. A range of other alkyl acrylates have been investigated and the control over the polymerisation is lost as the hydrophobicity of the polymer increases due to the increase in alkyl chain length indicating that it is important for the monomer to be soluble in the polar solvent

Synthesis of telechelic oligomers by atom transfer radical polymerization: A study of acrylate monomers

International audienceDifferent acrylate oligomers were synthesized by atom transfer radical polymerization in the presence of a transfer agent and CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine. The functionality in bromine was determined by 1H NMR. These oligomers were coupled in the presence of Cu(0) and the ligand 2,2-bipyridine. The coupling yield was determined by size exclusion chromatography and NMR analysis and depended on the nature of the monomer and not on the molecular weight. In other words, the preliminary functionalization of the brominated chain end with styrene increased the coupling yield

Chemical modification of lignin by phosphorus molecules to improve the fire behavior of polybutylene succinate

International audienceLignin 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

Use of Py-GC/MS and PCFC to characterize the surface modification of flax fibres

International audienceSurface modification of flax fibres with a phosphorous agent in a solvent process have been originally evaluated through thermal degradation using Pyrolysis Combustion Flow Calorimeter and Pyrolysis-Gas Chromatography/Mass Spectrometry. It has been highlighted that these techniques are particularly sensitive to the presence of the phosphonated grafting agent on natural fibres. After treatment, octadecylphosphonic acid (ODPA) was found to be covalently grafted on the flax fibres at a rate of almost 5%. For a better comprehension of the interactions between the phosphonic group and flax, the reactivity of the phosphonic acid function of ODPA with the main components of fibres was assessed. The results showed that ODPA reacts strongly with lignin and at a lower degree with xylan (model for hemicellulose) whereas no reaction with cellulose was evidenced

NANOKOMPOZYTY NA BAZIE MIESZANINY POLIPROPYLEN/POLIAMID 6 Z UDZIA£EM TRZECH RÓ¯NYCH NANOGLINEK: STABILNOOEAE TERMICZNA I OGNIOODPORNOOEAE

International audienceNanocomposites of polypropylene/polyamide 6 blends based on three different nanoclays: thermal stability and flame retardancy Summary-The influence of various layered silicates: sepiolite (needle-like structure), halloysite (nanotube structure) or organomodified montmorillonite (lamellar structure) in combination with phosphorous flame retardants [ammonium polyphosphate (APP) and aluminum diethylphos-phinate (OP)] on the properties and morphologies of compatibilized PP/PA 6 blends has been investigated. Thermal degradation and fire retardancy of these blends were explored using TGA, cone calorimeter, pyrolysis flow combustion calorimeter (PCFC). Morphology of nanocomposites and residues as well of the chemical structure formed after cone calorimeter tests were investigated. The sepiolite/APP composition led to the better fire performance through the formation of a large amount of charred and expanded residue reinforced by the sepiolite fibres. The better com-pactness of this residue than that of the montmorillonite/APP one enables to account for the interest of sepiolite, whereas montmorillonite exerts the better fire retardant role, alone in the polymer blend. Keywords: mineral filler, nanocomposite, halloysite, sepiolite, flame retardancy.Streszczenie-Badano wp³yw ró¿nych warstwowych krzemianów: sepiolitu (struktura iglasta), haloizytu (struktura nanorurek) i organicznie modyfikowanego montmorylonitu (struktura p³yt-kowa), u¿ytych w uk³adzie z fosforowymi uniepalniaczami [poli(fosforanem amonu) (APP) lub dietylofosfin¹ glinu (OP)] na w³aoeciwooeci termiczne i ognioodpornooeae kompatybilizowanej mie-szaniny polimerów PP/PA 6. Degradacjê termiczn¹ oraz odpornooeae na ogieñ oceniano metod¹ TGA, za pomoc¹ kalorymetru sto¿kowego a tak¿e mikrokalorymetru pirolizy i spalania (PCFC). Morfologiê nanokompozytów oraz strukturê powsta³ej pozosta³ooeci po testach kalorymetrycz-nych badano za pomoc¹ skaningowej mikroskopii elektronowej (SEM). Zastosowanie uk³adu se-piolit/APP prowadzi do utworzenia na powierzchni próbki najwiêkszej ilooeci barierowej, zwêglo-nej pozosta³ooeci, dodatkowo wzmocnionej w³óknami sepiolitowymi, co umo¿liwia najlepsz¹ ochronê przed ogniem otrzymanego nanokompozytu. Wiêksza spoistooeae tej pozosta³ooeci ni¿ uzy-skanej w przypadku stosowania uk³adu montmorylonit/APP sk³ania do wiêkszego zainteresowa-nia glink¹ sepiolitow¹, mimo i¿ sam montmorylonit, u¿yty jako nape³niacz PP/PA 6 jest skutecz-niejszym oerodkiem uniepalniaj¹cym. S³owa kluczowe: nape³niacz mineralny, nanokompozyt, haloizyt, sepiolit, opóŸniacz palenia

Dispersion control of raw and modified silica particles in PMMA. Impact on mechanical properties, from experiments to modelling

International audienceStructure and properties of PMMA/silica composites were characterized by various methods including SEM, TGA, rheology, microscopic level evaluation of nano-reinforcement effect on properties. Static modulus and yield strength of PMMA are enhanced with silica incorporation regardless of their dispersion or functionalization. However, composites ultimate properties are strongly affected by fillers characteristics. As expected, better performances are associated to well-dispersed and functionalized silica. A finite element modelling with interface debonding through cohesive model and interfacial area is introduced to reproduce the sensibility of tensile test response to fillers surface functionalization. Experimental results confirmed this modelling: at constant low weight rate, ultimate composites properties are mostly affected by any microstructural changes. An analysis of local stress confirms the premature breakage of composite with pristine silica. Finally, by considering the expected properties, functionalization of silica is not always a necessity. Instead of particle functionalization, a dispersion protocol could be advantageously used to reach interesting composite properties

NANOKOMPOZYTY NA BAZIE MIESZANINY POLIPROPYLEN/POLIAMID 6 Z UDZIA£EM TRZECH RÓ¯NYCH NANOGLINEK: STABILNOOEAE TERMICZNA I OGNIOODPORNOOEAE

International audienceNanocomposites of polypropylene/polyamide 6 blends based on three different nanoclays: thermal stability and flame retardancy Summary-The influence of various layered silicates: sepiolite (needle-like structure), halloysite (nanotube structure) or organomodified montmorillonite (lamellar structure) in combination with phosphorous flame retardants [ammonium polyphosphate (APP) and aluminum diethylphos-phinate (OP)] on the properties and morphologies of compatibilized PP/PA 6 blends has been investigated. Thermal degradation and fire retardancy of these blends were explored using TGA, cone calorimeter, pyrolysis flow combustion calorimeter (PCFC). Morphology of nanocomposites and residues as well of the chemical structure formed after cone calorimeter tests were investigated. The sepiolite/APP composition led to the better fire performance through the formation of a large amount of charred and expanded residue reinforced by the sepiolite fibres. The better com-pactness of this residue than that of the montmorillonite/APP one enables to account for the interest of sepiolite, whereas montmorillonite exerts the better fire retardant role, alone in the polymer blend. Keywords: mineral filler, nanocomposite, halloysite, sepiolite, flame retardancy.Streszczenie-Badano wp³yw ró¿nych warstwowych krzemianów: sepiolitu (struktura iglasta), haloizytu (struktura nanorurek) i organicznie modyfikowanego montmorylonitu (struktura p³yt-kowa), u¿ytych w uk³adzie z fosforowymi uniepalniaczami [poli(fosforanem amonu) (APP) lub dietylofosfin¹ glinu (OP)] na w³aoeciwooeci termiczne i ognioodpornooeae kompatybilizowanej mie-szaniny polimerów PP/PA 6. Degradacjê termiczn¹ oraz odpornooeae na ogieñ oceniano metod¹ TGA, za pomoc¹ kalorymetru sto¿kowego a tak¿e mikrokalorymetru pirolizy i spalania (PCFC). Morfologiê nanokompozytów oraz strukturê powsta³ej pozosta³ooeci po testach kalorymetrycz-nych badano za pomoc¹ skaningowej mikroskopii elektronowej (SEM). Zastosowanie uk³adu se-piolit/APP prowadzi do utworzenia na powierzchni próbki najwiêkszej ilooeci barierowej, zwêglo-nej pozosta³ooeci, dodatkowo wzmocnionej w³óknami sepiolitowymi, co umo¿liwia najlepsz¹ ochronê przed ogniem otrzymanego nanokompozytu. Wiêksza spoistooeae tej pozosta³ooeci ni¿ uzy-skanej w przypadku stosowania uk³adu montmorylonit/APP sk³ania do wiêkszego zainteresowa-nia glink¹ sepiolitow¹, mimo i¿ sam montmorylonit, u¿yty jako nape³niacz PP/PA 6 jest skutecz-niejszym oerodkiem uniepalniaj¹cym. S³owa kluczowe: nape³niacz mineralny, nanokompozyt, haloizyt, sepiolit, opóŸniacz palenia

Influence of a treated kaolinite on the thermal degradation and flame retardancy of poly(methyl methacrylate)

International audienceModified kaolinite poly(methyl methacrylate) nanocomposites were prepared using successively in situ polymerization and melt blending methods. Pristine kaolinite (Kaol) was intercalated using two organic molecules dimethyl sulfoxide (DMSO) and dodecylamine. This treated kaolinite (TKaol) was exfoliated via in situ polymerization of MMA. The prepared blends were extruded with a commercially available PMMA and then injection molded. The thermal degradation and flammability of TKaol PMMA nanocomposites was compared to pure PMMA and also to PMMA nanocomposites filled with untreated Kaol. Results showed the influence of Kaol morphology on fire behavior of these nanocomposites. The use of exfoliated Kaol allowed a better thermal stability to be achieved and the decrease of peak heat release rate (PHRR) as revealed by the cone calorimeter tests. Moreover, TKaol PMMA nanocomposite enabled to maintain time to ignition close to that of PMMA while it was largely reduced with PMMA nanocomposites filled with untreated Kaol. Finally, exfoliated Kaol led to an efficient barrier effect due to the formation of a cohesive residue as highlighted by its mechanical strength

Nafion®-sepiolite composite membranes for improved Proton Exchange Membrane Fuel Cell performance.

Nafion®-sepiolite composite membranes were prepared, characterized and integrated in Membrane-Electrodes Assembly to be tested in fuel cell operating conditions. The influence of the sepiolite content and its modification on the membrane properties was carefully analyzed. The performances of the different MEAs were compared at different operating temperatures and under various relative humidity. The sulfonation of pristine sepiolite has improved its ion exchange capacity as well as that of composites membranes. The introduction of sepiolite in Nafion ® also allowed simultaneously to increase its water uptake and to improve its mechanical features. Much better performances were obtained at high temperature and low relative humidity with MEAs based upon Nafion®-sepiolite composite membranes compared to pure Nafion ® membranes (50 % more output power at 100 °C and 50 %RH)