Thermal stability and flammability studies of coated polymer powders using a plasma fluidized bed process

In this work, the thermal stability of organosilicon coatings, polyamide-6 powders and polyamide-6 clay nanocomposite powders coated with organosilicon are studied. The coatings were obtained from polymerization of 1.1.3.3-tetramethyldisiloxane (TMDS) monomer doped with oxygen using a cold remote nitrogen plasma (CRNP) process. A fluidized bed reactor using CRNP assisted polymerization was used to coat the polymer powders. The effect of oxygen addition to TMDS on the thermal stability was investigated. Oxygen addition to TMDS promotes the formation of more thermally stable coated polymers. In the case of the polyamide-6 clay nanocomposite, the Limiting Oxygen Index values were much improved. This shows that the deposits are effective fire retardant coatings.     

Interactions between chlorinated paraffins and melamine in intumescent paint—investing a way to suppress chlorinated paraffins from the formulations

It is known that acid source, carbon source and blowing agent are the main ingredients of an intumescent paint. Melamine and halogenated additives, such as polychlorinated alkanes (PCAs) are used as blowing agents, however, the legislation tends to prohibit the use of halogenated coumpounds for environmental reasons. The aim of our study is to investigate the mode of action of melamine and PCAs in an intumescent formulation. Their interactions are also studied. It is found that the combination of PCAs and melamine leads to more efficient systems. Spectroscopic analyses (FTIR and solid state ¹³C NMR) led us to conclude that when the intumescent paint was heated melamine condensed to create melem via Diels-Alder-type reaction. Melem could then react with PCAs leading to the stabilisation of the PCA-melamine mixture. The proposed mechanism of action led us to propose a method for the substitution of PCAs.     

Adhesion of human pathogenic enteric viruses and surrogate viruses to inert and vegetal food surfaces

Enteric viruses, particularly human Noroviruses (NoV) and hepatitis A virus (HAV), are key food-borne pathogens. The attachment of these pathogens to foodstuff and food-contact surfaces is an important mechanism in the human contamination process. Studies were done to investigate the nature of the physicochemical forces, such as hydrophobic and electrostatic ones, involved in the interaction virus/matrix but, at this day, only few data are available concerning surface properties of viruses and prediction of the adhesion capacity of one specific virus onto matrices is still very difficult. The purpose of this study was to propose a reference system, including a representative virus surrogate, able to predict as close as possible behaviour of pathogenic viruses in term of adhesion on inert (stainless steel and polypropylene) and food surfaces (lettuce leaves, strawberries and raspberries). The adhesion of human pathogenic enteric viruses, cultivable strain of HAV and non-cultivable strains of human NoV (genogroups I and II), have been quantified and compared to these of human enteric viruses surrogates, included the MNV-1 and three F-specific RNA bacteriophages (MS2, GA and Qβ). A standardized approach was developed to assess and quantify viral adhesion on tested matrices after a contact time with each virus using real-time RT-PCR. Methods used for virus recovery were in accordance with the CEN recommendations, including a bovine Enterovirus type 1 as control to monitor the efficiency of the extraction process and amplification procedure from directly extracted or eluted samples. The adhesion of human pathogenic viruses, ranging from 0.1 to 2%, could be comparable for all matrices studied, except for NoV GII on soft fruits. Adhesion percentages obtained for the studied surrogate virus and phages were shown to be comparable to those of HAV and NoV on inert and lettuce surfaces. The MNV-1 appeared as the best candidate to simulate adhesion phenomena of all human pathogenic enteric viruses on all studied surfaces, while MS2 and GA bacteriophages could be a good alternative as model of viral adhesion on inert and lettuce surfaces. These results will be usable to design relevant experimental systems integrating adhesion behaviour of enteric viruses in the assessment of the efficiency of a technological or hygienic industrial process.     

Nonwoven as heat barrier: Modeling of the efficiency of Carbtex fibers

In this work, we examine the use of nonwoven (NW) as heat barrier to protect a metallic substrate. Carbtex fibers consisting in a thermoplastic core inside an oxidized outer shell (polyacrylonitrile or PAN fibers) are selected to make the NW. Measuring temperature profiles in a heat radiator test; it is revealed that Carbtex NW is an efficient heat barrier. A macroscopic model is then developed to simulate heat transfer in NW (considered as a porous medium) used as a protective heat barrier on aluminum plate. The model is validated comparing experimental results obtained by the heat radiator test and predicted values. The efficiency of NW layer is simulated varying different parameters characteristic of the NW (porosity and heat conductivity) and of the design (thickness of the layer). It is revealed to get good efficiency of the NW heat barrier that heat conductivity of the fibers is crucial to get superior performance as well as high porosity (higher than 0.5) associated with a reasonable thickness of NW (5–7 mm). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Carbonization mechanisms resulting from intumescence association with the ammonium polyphosphate-pentaerythritol fire retardant system

In this work we study the thermal behavior of an ammonium polyphosphate-pentaerythritol mixture, fire-retardant additive for polyolefins and most particularly the carbonization process resulting from an intumescent phenomenon. The study has been carried out using Micro-Raman and ¹³C, ¹H, ³¹P NMR of the solid state spectroscopies. It is shown that the structure consists in phoscarbonaceous and polyaromatic species. These latter form an anisotropic structure above 280°C. This structure grows when the temperature increases. Finally, a reactional scheme of the carbonization of the intumescent system is proposed.     

Designing polylactide/clay nanocomposites for textile applications: Effect of processing conditions,spinning, and characterization

An experimental study was carried out to design polylactide (PLA)-clay nanocomposites for developing fibers. PLA and 1–10 wt % of a selected organomodified bentonite (Bentone® 104-B104) were melt mixed to examine the effect of processing conditions (temperature, shear, residence time) on the morphology of performed polymer nanocomposites (PNC). Because of a good compatibility with PLA matrix, the dispersion of B104 occurred under different conditions without difficulty, and a similar morphology was obtained. The results obtained showed that at low temperature of mixing, the shear stress exerted on polymer has a key role on the extent of intercalation and delamination. Upscale experiments were further performed using optimized conditions and 4 wt % B104 was added to PLA matrix by melt blending to produce PNC for spinning. Then, the recovered PNC were melt spun to produce multifilaments yarns, and it was demonstrated that surprisingly, it is not necessary to use a plasticizer to spin a blend with 4 wt % B104. The properties of the yarns have been studied in terms of clay dispersion as well as thermal, mechanical, and shrinkage properties. B104 could be added up to 4 wt % into PLA without detrimentally sacrificing the tensile strength of melt-spun filaments, especially at high draw ratio. Interestingly, the PNC-based multifilaments were knitted and the flammability studied using cone calorimeter at 35 kW/m². A strong decrease, up to 46%, of the heat release rate was measured. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Zeolites: New Synergistic Agents for Intumescent Fire Retardant Thermoplastic Formulations—Criteria for the Choice of the Zeolite

The adduct of zeolites in intumescent formulations of thermoplastic polymers (additives: ammonium polyphosphate and pentaerythritol) leads to a great improvement in their fire retardant performance. A classification of different groups (A, X, Y, Mordenite and ZSM-5) is presented. The influence of the physicochemical properties of the zeolites is discussed. TG analyses reveal that the zeolite may act as a catalyst for the development of the intumescent carbonaceous material and stabilize the carbonaceous residue resulting in the degradation of the intumescent shield. Characterized by MAS-NMR ²⁷Al and ²⁹Si, it is proposed that alumino- and silicophosphate species formed are catalysts active for the synthesis of a protective carbon-based material.