José-Marie Lopez-Cuesta

Red phosphorus/aluminium oxide compositions as flame retardants in recycled poly(ethylene terephthalate)

Abstract The mechanical properties and fire resistance of a recycled poly(ethylene terephthalate) were improved by using a specific treatment of the waste material and the incorporation of encapsulated red phosphorus in combination with co-additives. The use of red phosphorus has to be limited due to a negative influence on impact resistance and rate of heat release. Among several metal oxides, Al 2 O 3 acts as a good co-synergist at a total loading of 5 wt.% due to its reactivity, high specific surface area and aluminium phosphate formation. The complementary use of glass fibres can also generate intumescence by improving the mechanical stability of the char layer.

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate)/Polylactide Blends: Thermal Stability, Flammability and Thermo-Mechanical Behavior

Blends of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactide (PLA) with different PHBV/PLA weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) were prepared by melt compounding. Their mutual contributions in terms of thermal stability, flammability resistance, mechanical properties and rheological behavior were investigated. The study showed that the increase in PLA content in PHBV/PLA blends leads to enhanced properties. Consequently, thermal stability and flammability resistance were improved. Further, the rheological measurements indicated an increase in storage modulus and loss modulus of PHBV matrix by addition of PLA.

Behavior and Fate of Halloysite Nanotubes (HNTs) When Incinerating PA6/HNTs Nanocomposite

Nanoclay-based nanocomposites have been widely studied and produced since the late 1990s, and frequently end up in waste disposal plants. This work investigates the behavior of PA6/HNTs nanocomposites (nylon-6 incorporating halloysite nanotubes) during incineration. Incineration tests were performed at lab-scale using a specific tubular furnace modified in order to control the key incineration parameters within both the combustion and postcombustion zones. The combustion residues and combustion aerosol (particulate matter and gas phase) collected downstream of the incinerator furnace were characterized using various aerosol analysis techniques. Time tracking of the gas and particle-number concentrations revealed two-step char formation during combustion. HNTs transformed into other mineral structures which were found in both the aerosol and the residues. During combustion of the polymer, it appears that HNTs contribute to the formation of a cohesive char layer that protects the residual material.

Synthesis of polyphosphorinanes Part II. Preparation, characterization and thermal properties of novel flame retardants

We report here the investigation of new flame retardant compounds for textiles, obtained by radical polymerization of allyloxydioxaphosphorinanes. These monomers were first synthesized by a transesterification reaction. A deep NMR study of such compounds revealed the existence of diastereoisomers Z and E. Radical polymerizations of allyloxydioxaphosphorinanes in the presence of a chain transfer agent, i.e.dimethylhydrogenophosphonate, led to oligomers of rather low molecular weights and especially adducts with DP 1 and 2. It was demonstrated that radical polymerization of allyloxydioxaphosphorinanes with P–R (R being alkyl or aryl) does afford only linear oligomers instead of hyperbranched polymers when R is hydrogen. The thermogravimetric analyses of the oligomers showed a good thermal stability and a high content of char residue (more than 16 wt%). The flame retardant properties were also evaluated by microcalorimeter tests and revealed an efficient behavior especially in the condensed phase, comparatively to Antiblaze 19®, the flame retardant commercial product for polyester textile.

Influence of impurities on the performances of HIPS recycled from Waste Electric and Electronic Equipment (WEEE).

In order to produce a high quality recycled material from real deposits of electric and electronic equipment, the rate of impurities in different blended grades of reclaimed materials has to be reduced. Setting up industrial recycling procedures requires to deal with the main types of polymers presents in WEEE (Waste Electric and Electronic Equipment), particularly High Impact Polystyrene (HIPS) as well as other styrenic polymers such as Acrylonitrile-Butadiene-Styrene (ABS), Polystyrene (PS) but also polyolefin which are present into WEEE deposit as Polypropylene (PP). The production of a substantial quantity of recycled materials implies to improve and master the compatibility of different HIPS grades. The influence of polymeric impurities has to be studied since automatic sorting techniques are not able to remove completely these fractions. Investigation of the influence of minor ABS, PS and PP polymer fractions as impurities has been done on microstructure and mechanical properties of HIPS using environmental scanning electron microscopy (ESEM) in order to determine the maximum tolerated rate for each of them into HIPS after sorting and recycling operations.

Gaseous effluents from the combustion of nanocomposites in controlled-ventilation conditions

Composite materials are more and more used every day. In order to further enhance their attractive mechanical and physico chemical performances, the last generation of these materials largely makes use of nanomaterials. Various nanofillers are eligible for such a purpose, the best ones depending on the associated matrices. One favorite field of application of these nanomaterials is fire retardancy and fire behavior of nanocomposites. In the context of the ANR research project NanoFeu, various technical analyses have been performed [1]. One focuses on the characterization of the dispersion of nanofillers in the matrix; another deals with the characterization of the fire behavior of samples including the study of the composition of the gaseous effluents, the characterization of the emitted soot [2]. A third part of the work focused on molecular modeling of observed phenomena within the matrices. This paper focuses mainly on the combustion of nanocomposite samples under various ventilation conditions. Tests have been performed with the Fire Propagation Apparatus (FPA). Samples are based on poly(methyl methacrylate); various nanofillers were used: carbon nanotubes, alumina and silica. Efficiency of fillers is compared to the classical ammonium polyphosphate in equal proportions. During testing, the ventilation-controlled conditions were obtained by adjusting the combustion air flow rate entering the apparatus. Gaseous effluents were analyzed by Fourier Transform Infra-Red spectrometer. Fire behavior is characterized in terms of fire parameters and chemical composition of gaseous effluents. The influence of ventilation conditions is especially significant in terms of amount of gases released: much more important production of specific gases is generally observed in case of under ventilation regime as compared to the well ventilated case.

Adhesive properties of silicone polymers on some typical opto-electronic substrates: influence of the network density

Abstract This study examines the influence of the microstructural properties of a silicone polymer network and the surface properties of opto-electronic substrates on the adhesive properties. We highlighted the influence of the silicon network microstructure on the type of break between the silicon polymer and the substrate: from an adhesive to a cohesive break when the cross-links density decreases with some formulations that give rise to some typical behaviours. Finite element analysis was used to explain these behaviours. We also showed that the quality of the interface evolves in function of the viscosity of the silicon polymer before cross-linking and the number of Si–H functions it has. A better adhesion on silicon polymer/silica than on silicon polymer/InP is ascribed to the chemical composition surface being similar to the chemical structure of the silicon polymers and to more favourable surface energies.

Thermal degradation and flammability of polyamide 11 filled with nanoboehmite

Abstract The flame-retardant effect of rod-like nanoboehmite was evaluated in biobased polyamide 11. Thermal analysis reveals that hydrated nanofillers modify the degradation pathway of polyamide 11 turning from a two-step to a single-step mechanism. The polymer thermal stability is increased due to interactions between polar groups and filler surface hydroxyl groups. Despite this improved thermal stability, polyamide 11/nanoboehmite composites exhibit shorter times to ignition in cone calorimeter. The phenomenon was attributed to changes in thermoradiative properties leading to a faster heating of the polymer surface. The most significant flame-retardant action is a reduction in heat release rate that was related to a barrier effect while endothermic water release seems to play a minor role.

Flame Retardancy of Natural Fibers Reinforced Composites

Due to numerous advantages (high specific mechanical properties, low density, biosourcing, …), natural fibers from plants are considered as credible alternatives to glass or carbon fibers for composites industry. Nevertheless, their relatively high flammability limits their potential applications. Many researches have been carried out to improve the flame retardancy of composites reinforced with natural fibers. This chapter attempts to establish the state-of-art of these researches.

CHAPTER 12:Flame Retardancy of Phosphorus-Containing Polymers

In this chapter the influence of phosphorus incorporated through a reactive approach on the flame retardancy of polymers is reviewed. Phosphorus modifies the degradation pathway of the polymer and hence its thermal stability and charring. Its activity in the vapor phase would be also an additional mode of action. The influence of the chemical environment on the efficiency of phosphorus as flame retardant is also discussed.