A novel environmentally friendly recycling method is developed for large carbon-fibers reinforced-polymers composite panels whose efficiency is demonstrated through a proof-of-concept fabrication of a new composite part based on recycled fibers. The recycling process relies on formic acid as separation reagent at room temperature and atmospheric pressure with efficient recycling potential of the separating agent. Electron microscopy and thermal analysis indicate that the recycled fibers are covered by a thin layer of about 10wt.% of residual resin, alternating with few small particles, as compared to the smooth virgin fibers. The recycled composites show promising shear strength and compression after impact strength, with up to 93% retention of performance depending on the property as compared to the reference. The recycled carbon fibers can thus be reused for structural applications requiring moderate to high performances. The loss of properties is attributed to a lower adhesion between fresh epoxy resin and recycled carbon fibers due to the absence of sizing, partly compensated by a good interface between fresh and residual cured epoxy thanks to mechanical anchoring as well as chemical reactions. The room temperature and atmospheric pressure operating conditions combined to the recyclability of the forming acid contribute to the sustainability of the entire approach.

The specific influence of polyethersulfone (PES) end‐functionalization with chlorine or hydroxyl end groups at same molar mass on PES‐epoxy composites based on a high‐performance tetra‐epoxide with di‐amine hardener resin (RTM6) is investigated in terms of morphology, thermal behavior, and toughness. A model study on PES filaments embedded in epoxy precursor is first performed to compare the interdiffusion and resulting morphology upon curing. PES‐OH shows a larger interdiffusion distance compared to PES‐Cl in the model systems and the laminates. This effect is more pronounced at high heating rate. Cross sections and fracture surfaces of composite panels are analyzed by scanning electron microscopy (SEM) coupled with energy dispersive X‐ray (EDX) spectroscopy to establish the link between the microstructures and fracture mechanisms. The toughness of PES‐OH‐modified epoxy composites is doubled compared to unmodified reference panels, whereas the PES‐Cl shows no improvement. The favorable influence of PES‐OH is ascribed to enhanced miscibility, interfacial adhesion and morphology, resulting from the better affinity between hydroxyl‐terminated PES and the epoxy‐resin. POLYM. ENG. SCI., 59:996–1009, 2019. © 2019 Society of Plastics Engineers

Ecofriendly fully bio-composites based on polyamide 11 (PA11) and lignin have been prepared on the entire concentration range using a twin-screw extruder. In this work, PA11 was blended with lignin by direct extrusion technology without any chemical pre- or in-situ- modifications or physical pretreatments. The presence of various organic and inorganic impurities in the selected technical lignin have been maintained. The incorporation of this cheap renewable material from biomass in bio-based PA11 was inspected by an array of characterization tools. Also, the effect of the presence of lignin on the morphology and on the mechanical properties of the resulting materials was examined. Finally, in-situ investigation of structural evolution in PA11 induced by the presence of lignin was analyzed by Fast Scanning Chip Calorimetry.

The interdiffusion between a low and a high viscosity epoxy resin was studied on model systems representing the novel composite manufacturing process called “Same Qualified‐Resin Transfer Molding” (SQ‐RTM). Neat resin model systems were first characterized after curing by Raman spectroscopy, energy dispersive X‐ray microscopy, and nano‐indentation, all methods reveal an interdiffusion distance of about 700–900 µm. Transmission electron microscopy further revealed a complex morphological gradient structure in the interdiffusion zone. The interdiffusion distance was about 800 µm in the absence of carbon fibers, reducing down to 500 µm when the viscous resin was replaced by the corresponding prepreg, due to the geometrical constraints imposed by the fibers. Moreover, some asymmetry was observed in the interdiffusion profile because of the viscosity difference between the resins. The results obtained on the model systems were found to match very well the interdiffusion profiles generated in real SQ‐RTM composites processed with the same combination of resins. POLYM. ENG. SCI. 56:1061–1069, 2016. © 2016 Society of Plastics Engineers

Composites composed of polyesters, poly(butylene succinate) (PBS) or poly[(butylene succinate)-co-(butylene adipate)] (PBSA), and 5 wt% of montmorillonite (CNa) or organo-modified montmorillonite (C30B) were melt-processed and transformed into films by either compression-molding or extrusion-calendering. XRD, rheological measurements and TEM images clearly indicated that films containing CNa are microcomposites, while nanocomposites were observed for those containing C30B. Using Flash DSC, it was possible, for the first time, not only to measure the heat capacity step at the glass transition of these two materials in their amorphous state, but also to investigate whether the preparation technique influenced the Rigid Amorphous Fraction (RAF) in our PBS- and PBSA-based nanocomposites. In this work, we have successfully shown the correlation between the microstructure of the films and their barrier properties, and especially the role played by the RAF. Indeed, the lowest permeabilities to gases and to water were determined in the films containing the highest RAF in both PBS- and PBSA-based materials.

The use of phenoxy nanocomposite films as carriers of nanofillers involving multiwalled carbon nanotubes and nanoclays is successfully demonstrated for application in epoxy carbon fibers reinforced composites (CFRC) processed by RTM. Model studies on individual nanocomposite filaments embedded in epoxy precursors show that the nanofillers are passively transported by the interdiffusion gradient during heating over distance around 800μm. A morphology gradient is generated after reaction induced phase separation and the nanofillers end up in the epoxy, despite their initial dispersion in the phenoxy. The proof of concept is extended to CFRC panels where nanocomposite phenoxy films are prepositioned between every odd carbon layer of the preform. Carbon nanotubes are filtered by the carbon fabrics, which limits their full diffusion and that of phenoxy through the preform. This has negative consequences on fracture toughness (GIc). For nanoclay, GIc is rather slightly improved although the origin is not fully clear.

We explore the influence of the interdiffusion of two thermoplastic tougheners and RTM6 epoxy resin precursors on the resulting morphologies after curing and the consequences on delamination toughness of the corresponding carbon fiber reinforced composites. Two thermoplastics with contrasting Tg and compatibility, i.e. poly(ether sulfone) (PES) and phenoxy are compared. The dramatic improvement of the interlaminar fracture toughness (GIC) found for the phenoxy-RTM6 system as compared to the pure thermoset reference can be ascribed to the broad morphology gradient only observed for that system. By contrast, the PES-RTM6 system is characterized by a steep morphology gradient and a corresponding decrease of as compared to the reference.

In this study, polyamide 12 (PA12)/untreated halloysite nanotubes (HNTs) nanocomposites are prepared in a semi-industrial scale extruder using a non-traditional one step water-assisted extrusion process. A morphological study is carried out using a combination of scanning electron microscopy and transmission electron microscopy analyses to evaluate the influence of water injection and filler content on the quality of clay dispersion. The use of water injection slightly improves the nanoscale dispersion at low HNTs content (<8wt.%), while this effect is more pronounced at higher filler loading (16wt.%). A mechanism explaining the physico-chemical action of water during extrusion is proposed. The materials are characterized with respect to their mechanical, thermo-mechanical, thermal and fire properties. A strong correlation is found between nanostructure and physical properties; the more uniform dispersion of the clay nanotubes, the higher mechanical reinforcement, thermal stability and fire retardancy of PA12 nanocomposites. Tensile tests results are interpreted in terms of three mechanical models: the Halpin-Tsai's model for stiffness and the interfacial strength model and the Pukanszky's equation for yield strength. Linear fits of the experimental data confirm that the superior reinforcement of nanocomposites prepared using water injection results from improved clay dispersion and better interfacial adhesion between PA12 and HNTs. In view of these promising results, the proposed direct melt compounding method could be easily scaled-up towards the production of PA12-HNTs nanocomposites at an industrial scale. Copyright (c) 2013 John Wiley & Sons, Ltd.

This study shows the interest of elaborating polylactide/halloysite nanocomposites by means of water assisted extrusion (WAE). Besides, WAE gives access to materials with improved fire properties and prevents molecular degradation.

This paper presents a study of polyethersulfone (PES)/halloysite nanotube (HNTs) nanocomposites prepared by melt compounding either through a simple extrusion process or via a water-assisted extrusion procedure. Scanning and transmission electron microscopy techniques are combined with rheological measurements to assess the influence of polymer end groups (–Cl or –OH) and water injection on the HNTs dispersion state. A morphological transition form microcomposite to nanocomposite is achieved when replacing –Cl chain ends of PES by –OH groups, especially when water is injected during processing. By a combination of Soxhlet extraction and thermogravimetric analysis, we show that some PES(OH) chains are covalently bonded onto the aluminosilicate surface during extrusion. A mechanism describing the physico-chemical action of water is presented. The best system in terms of clay dispersion has been retained to characterize PES-HNTs nanocomposites with respect to their thermo-mechanical, thermal and fire (mass loss calorimetry and UL-94) properties. Dynamic mechanical analysis shows a significant enhancement in the storage modulus of halloysite-based nanocomposites when compared to the unfilled matrix. The improved thermal and thermo-oxidative stability of PES in presence of HNTs is mainly attributed to the labyrinth effect provided by individually dispersed nanotubes, which is reinforced during the decomposition process by the formation of a protective charred ceramic surface layer. The mechanism of action of HNTs for fire retardancy of PES presumably arises from a synergistic effect between physical (i.e. ceramic-like structure formation and mechanical reinforcement of the intumescent char) and chemical (i.e. charring promotion) processes taking place in the condensed phase. According to this study, the straightforward and cost-effective melt compounding route could pave the way for future development of high-performance nanoscale polymeric materials combining enhanced thermal properties and excellent flame retardant behaviour.

This work aims to evaluate the efficiency of halloysite as synergistic agent in an intumescent PP system based on a coated ammonium polyphosphate (IFR). The first part of the study analyses the thermal stability and fire performance of PP when using the intumescent formulation alone or in combination with the aluminosilicate nanotubes (HNTs). Cone calorimetry reveals that partial substitution of IFR by HNTs (3 wt.%) imparts substantial improvement in flame retardancy with reduced heat release rate and longer burning times. Additionally, a shift from V-1 to V-0 classification is achieved at the UL-94 test with only 1.5 wt.% HNTs. The second part provides a better understanding of the physical and chemical mechanisms of action of HNTs in the intumescent systems. The chemical evolution of the condensed phase during combustion is described by solid state NMR, and in particular using 2D NMR. Results indicate that halloysite speeds up the development of the intumescent shield, but also enhances its mechanical properties by physical reinforcement (i.e. aluminosilicate "skeleton-frame" for the phosphocarbonaceous structure) and/or by chemical interactions with IFR yielding to aluminophosphates. These new chemical species allow thermal stabilization of the char at high temperatures and provide good macro- and micro-structural properties. Both effects increase the mechanical strength of the protective layer during burning ensuring excellent heat and mass transfer limitations between gas and condensed phases. (C) 2013 Elsevier Ltd. All rights reserved.

Polymer based nanocomposites are a new broad class of materials widely used in a large range of applications as they generally exhibit improved properties compared with the neat polymer. These materials have been known for a few decades and they have been widely studied in academia and industries, regarding their preparation and properties characterization. More recently, environmental, health and public concerns related to air quality have imposed severe worldwide rules regarding the emissions of Volatile Organic Compounds (VOCs), odours and nanoparticles from such materials. Indeed some studies have shown that they may exhibit some risks to human health. In this study, measurements of VOCs, odours and nanoparticles emissions have been carried out on polyether-block-amide copolymer (PEBA) clay nanocomposites. Both the processing and the storage stages have been investigated. These measurements revealed that nanocomposites based on Cloisite (TM) 30B exhibit stronger odour than sodium montmorillonite (MMT) and that this may constitute a significant drawback for industrial applications despite their outstanding properties. This behaviour has been explained considering the nature of the emitted VOCs (Volatile Organic Compounds). Particularly it has been highlighted that potentially unhealthy compounds can be emitted during the storage of the material. Moreover, another processing route has been tested as an alternative to the use of organo-modified clays. This consists in injecting water during extrusion, with the aim of dispersing untreated MMT in order to get an exfoliated morphology. Measurements have revealed that in addition to substantial savings that can be achieved using this method, it also reduces emissions both during processing and further use, as compared with conventional processes. (C) 2012 Elsevier Ltd. All rights reserved.

In this work, halloysite nanotubes (HNTs) are used to prepare a polypropylene (PP)/HNTs nanocomposite via a melt blending process. The thermal stability of PP/clay nanocomposite compared to virgin PP is investigated in both inert nitrogen and air atmospheres using thermogravimetric analysis. The model-free isoconversional method according to Friedman is used to estimate activation energies as a function of the conversion degree. The thermal behavior of PP and PP/HNTs 8 wt% nanocomposite is then modeled and simulated. A very good agreement, especially under nitrogen, is obtained between simulated curves and experimental ones, both in dynamic and isothermal conditions. Activation energies of the PP/HNTs nanocomposite increase compared to pure PP, whatever the degradation conditions. These results correlate well with the higher thermal stability of PP observed in presence of halloysite nanotubes, as well as the reduced flammability of PP/HNTs nanocomposites reported in a previous study. (c) 2012 Elsevier Ltd. All rights reserved.

For decades, kieselguhr has been the most common filter aid for beer filtration. However, costs for disposal are severely increasing and brewers today are concerned about replacing kieselguhr filtration by a greener technology. Filtration trials were carried out with the regenerable filter aid oxidized high-density polyethylene (OxPE) on a pilot-scale candle filter using green lager beer from settling tanks. OxPE has an average particle size distribution of 37 μm and its outer surface presents nodular structures. The porosity of the OxPE media is 0.6 compared with 0.85 for kieselguhr. OxPE retains a good amount of haze and yeast cells without clogging; however, the expected clarity was reached only when using Brewtan. The use of polyvinyl-polypyrrolidone (PVPP) mixed with the OxPE filter aid (25/75%) showed the best results for filtration because of the shape of PVPP particles and their slight compressibility. Regeneration is one of the most important steps to achieve because the filter aid has to be reused as many times as possible while keeping its properties of retention toward haze and yeast cells. OxPE proved to have very good resistance to aggressive regeneration conditions, and filtration trials carried out after such an operation confirmed this.

Polyamide 6 (PA6)/clay nanocomposites, based on organo-modified and pristine (i.e. purified but non-modified) montmorillonite, were prepared using a water-assisted extrusion process based on the injection of water during extrusion. The formation of a single PA6/water phase during extrusion (shown by High Pressure Differential Scanning Calorimetry (HPDSC)) improves the clay dispersion, decreases the PA6 melting temperature by 66°C (so-called cryoscopic effect), and thus prevents the polymer matrix degradation during processing. This process enables the compounding of pristine clay-based nanocomposites whose dispersion state, thermal and mechanical performances are close to what is generally reported for organo-modified montmorillonite-based nanocomposites. Advantage was taken of water-assisted extrusion to optimize the clay dispersion by increasing shear rate and of the cryoscopic effect to limit the degradation by decreasing the processing temperature. Using these conditions PA6/pristine clay nanocomposites properties are similar to those of more conventional PA6/organomodified clay nanocomposites.

Polyether-block-amide (PEBA) /clay nanocomposites were prepared water-assisted by twin-screw extrusion. Both organomodified and pristine (i.e. purified but non-modified) montmorillonite clays were used. A high-pressure differ- ential scanning calorimetry analysis carried out in the processing conditions demonstrated that PEBA/water blend exhibits some miscibility and that amide blocks and water behave as a single phase. In addition to a significant decrease of the melt- ing temperature, water injected into the melt plays a key role among the filler dispersion and prevents the matrix from degradation during melt-extrusion. This process enables the compounding of pristine clay-based nanocomposites whose dispersion state is high enough for the resulting mechanical performances in tension to be at least equivalent to what is reached with organomodified clay. Effects of the nanofiller dispersion onto the macromolecules' mobility are detailed and fracture mechanisms are identified for the various structures.

THERMAL BEHAVIOUR OF POLYPROPYLENE/HALLOYSITE NANOTUBES NANOCOMPOSITES: WATER-ASSISTED EXTRUSION B. Lecouvet*, M. Sclavons, S. Bourbigot, J. Devaux, C. Bailly a Bioand Soft Matter (BSMA), Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain (UCL), Croix du Sud 1 box 4, 1348 Louvain-La-Neuve. Belgium and b Unité Matériaux et Transformations, Ecole Nationale Supérieure de Chimie de Lille (ENSCL), 59652 Villeneuve d’Ascq. France.

Polyamide 12 (PA12) nanocomposites based on halloysite nanotubes (HNTs) were obtained using a batch internal mixer or a twin-screw mini-compounder. In order to analyze the influence of HNTs dispersion on nanocomposite properties, morphological analysis (SEM and TEM) was combined with rheological and thermo-mechanical experiments. The linear viscoelastic properties and the dynamic storage modulus were expectedly found to increase with increasing HNT loading. Higher enhancements were observed for PA12/HNTs nanocomposites obtained by twin-screw mini-compounding. This finding was related to the better degree of dispersion and alignment of the silicate nanotubes throughout the matrix. Thermal stability was also improved by the halloysite nanotubes presumably by an entrapment mechanism of the volatile products inside the hollow tubular structure. DSC measurements further highlighted a nucleation effect of HNTs on the nanocomposites. In view of these results, halloysite nanotubes are promising candidates in the field of PA nanocomposites for structural applications.

Nanocomposites based on polypropylene (PP) and unmodified Montmorillonite were prepared using a novel elaboration route based on a water-assisted extrusion process. Unmodified Montmorillonite, high shear compounding together with injection of aqueous suspension and reactive processing technology were used. Different aqueous suspensions containing cationic or anionic surfactants, and a compatibilizer (PP-g-MA) were injected during extrusion to promote clay dispersion. For a comparison purpose, a commercial PP/clay masterbatch was melt mixed to PP. Structural, morphological, and rheological characterizations indicate clearly that the cationic suspensions ease the dispersion of clay platelets in the PP matrix. No full exfoliation is, however, obtained, and the system remains still less homogeneous than the nanocomposite based on the commercial masterbatch. Nevertheless, mechanical and thermal characterizations of the nanocomposites based on cationic surfactants demonstrate the efficiency to disperse clay in the polymer matrix, and the effect on the ductility compared to usual PP nanocomposites is promising. POLYM. ENG. SCI., 49:2276-2285, 2009. (C) 2009 Society of Plastics Engineers

This work investigated the ability of several lands of molecules to mediate the melt functionalization of polypropylene N-Bromosuccinimide, nitroxides, iniferters, thiols and RAFT chain transfer agents were tested as potential mediators. The grafting of maleic anhydride onto polypropylene was carried Out With and without mediator and the grafted polymers are discussed in terms of graft content, graft structure and molecular weights (C) 2009 Elsevier Ltd All rights reserved