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Two phosphorus-based molecules were grafted onto flax fibers through electron beam irradiation in order to impart flame retardancy to flax fabrics. Fabrics were impregnated by dipping them into a solution containing a phosphonated monomer: dimethyl(methacryloxy)methyl phosphonate (MAPC1) or dimethylvinyl phosphonate (MVP). Then fabrics were irradiated at a dose ranging between 10 and 100 kGy. The grafting efficiency was found to be dependent on the molecule concentration in the impregnation solution, on the radiation dose and on the nature of the monomer. In particular, it has been observed that MAPC1 is grafted only onto the surface while MVP is also grafted into the bulk leading to high phosphorus content (4 wt%). Flame retardancy of the modified flax fibers, fabrics and polyester thermoset composites containing these fabrics were also investigated. High phosphorus content allows fabrics to achieve self-extinguishing behavior. The flammability of composites in cone calorimeter test is also reduced, even if the thermoset is not flame retarded itself.

a b s t r a c tLignin 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.

Flax fabrics were modified through two grafting methods in order to improve their flame retardancy. Vinyl phosphonic acid was used to treat flax fabrics via a condensation reaction between phosphonic acid function and flax hydroxyl groups. It was also grafted under radiation conditions taking advantage of its carbon-carbon double bond. Grafting efficiency of each method was assessed by X-ray fluorescence and scanning electron microscopy. The effect of the phosphorus grafting on fire behavior was studied using thermogravimetric analysis, pyrolysis combustion flow calorimetry and a preliminary fire test. In all cases, the diffusion of the phosphorus molecules into the elementary fibers bulk was observed. Phosphorus content reached 1.4 wt% using radiation grafting, leading to self-extinguishing fabrics.

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et al.. Nafion®-sepiolite composite membranes for improved proton exchange membrane fuel cell performance.

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Summary: Atom Transfer Radical Polymerization (ATRP) of styrene was carried out at 110 °C using various substituted 2‐bromoisobutyrates as initiators and the homogeneous catalyst CuBr/1,1,4,7,10,10‐hexamethyltriethylenetetramine (HMTETA). Telechelic oligomers were obtained by coupling the bromo terminated polymers using Cu(0)/PMDETA catalyst at 90 °C. The products were characterized by 1H NMR and MALDI‐TOF and some unsaturated polymer chains were observed. They could originate from either disproportionation reaction or dehydrohalogenation of halogen terminated oligomers during MALDI analysis. Using this method, polymers with hydroxy, acid, or ester end groups were synthesized in a range of molecular weights from 1 000 to 13 000 g · mol−1. Coupling efficiency was between 79 and 100%, depending on the structure of the initiator.Coupling reaction of substituted polystyrenes using Cu(0)/PMDETA system at 90 °C.imageCoupling reaction of substituted polystyrenes using Cu(0)/PMDETA system at 90 °C.