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Recycling of CFRP composites based on a thermoplastic matrix (ELIUM 150) which can be infused and cured at room temperature - Recovery of the matrix by dissolution processes and testing of fibre damage by means of SEM and single fibre tensile tests
Abstract and Figures
With the ELIUM resin, the French company ARKEMA S.A. has for the first time developed a thermoplastic matrix system that can be infused and cured at room temperature. Thus, in comparison to other thermoplastic systems, Elium does not require high processing temperatures. This behaviour enables the resin system to be processed in simple production processes otherwise reserved for thermoset systems, such as VARI. This simplified processability opens the opportunity of an increased use of thermoplastic matrix systems in FRCs in the future which are in principle recyclable. In the context of the circular economy concept, it is therefore essential to explore methodologies for the recyclability of the system during its development and market introduction phase.
In the context of the investigation of the recyclability of this resin system as well as the recovery of carbon fibre, a dissolution strategy for matrix extraction from the CFRP is presented. The solubility of the matrix from the CFRP in acetone is investigated at room temperature and at 40°C. Subsequently, the recovered fibres are examined for failure strength by means of single fibre tensile tests and surface features by means of SEM imaging. Finally a second generation composite will be produced using the recycled carbon fibres and fresh resin via VARI and the thermo-mechanical properties are compared.
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... Gebhardt et al. [99] se sont intéressés à un protocole de recyclage par dissolution à température ambiante de composites carbone à base d'Elium® 150. Il s'agit de recycler des éprouvettes de composites de 200 x 180 mm 2 (composites de première génération). ...
... Si la résine est trop visqueuse (Cf. Figure I-22), cela implique que la dissolution du composite ne sera pas efficace. [99] Les résultats des temps nécessaires à la dissolution de la résine Elium® obtenus par les mêmes auteurs sont donnés dans le Tableau I-13, en fonction du solvant et du ratio. L'Elium® 150 recyclé dans l'acétone montre un spectre infrarouge très similaire à celui du matériau initial (Cf. ...
... Tableau I-14 : Température de transition vitreuse moyenne de la résine Elium® vierge et après recyclage [99] Les auteurs expliquent cette augmentation de la Tg après le recyclage par une polymérisation probablement incomplète lors de la production et donc la présence de monomères résiduels. La polymérisation peut se poursuivre pendant l'étape de dissolution et de séchage du processus de recyclage. ...
Les réglementations environnementales poussent l’industrie automobile à développer de nouveaux matériaux plus légers et moins polluants. Les matériaux composites sont déjà de plus en plus présents et constituent près de 20% en masse d’un véhicule. En effet, ces derniers présentent de nombreux avantages en terme de propriétés thermomécaniques au cours de leurs conditions d’usage et de potentiel de recyclabilité. Cependant, actuellement les composites à matrices thermodurcissables dont les performances mécaniques ne sont plus à vérifier constituent principalement la structure d’un véhicule. Ces matériaux ne se recyclent pas ou très difficilement. C’est pourquoi l’objectif de cette thèse repose sur l’emploi des composites à matrice thermoplastique à fibres longues de basalte et de verre mis en œuvre par infusion grâce au développement de la résine Elium® par Arkema.Connaître l’impact des conditions d’usage de ces composites Elium®/verre et Elium®/basalte sur leurs propriétés mécaniques et étudier leur potentiel de recyclage à travers différentes voies : mécanique et chimique par dissolution sont les deux volets de la thèse. Il a été démontré que ces composites présentent une bonne tenue structurelle et des performances thermomécaniques satisfaisantes face à des conditions d’exposition hygrothermiques, UV ou naturelles. Dans le cas d’un recyclage mécanique, un protocole adapté a pu être établi pour une réincorporation des broyats de composites en tant que renforts dans un matrice polyamide-6 leur conférant de propriétés similaires à celle d’un composite PA6/fibres de verre ou de basalte non recyclées, et ce quelle que soit l’architecture initiale (toile, multiaxe) du renfort. Dans le cas du recyclage chimique par dissolution, il a été montré que la résine Elium® n’est pas dégradée et que les tissus peuvent être réutiliser pour produire des composites Elium®/verre et Elium®/basalte de seconde génération avec des propriétés mécaniques équivalentes aux composites initiaux.
... The Elium 150 thermoplastic resin system, developed by Arkema in 2014, offers promising opportunities to recover both fibres and matrix in good quality using a new dissolution based recycling process different to the three common recycling methods for composites [17][18][19][20]. Elium is a room temperature polymerisable and infusible thermoplastic matrix consisting of acrylic acid, methacrylic acid and their methyl esters along with other acrylic copolymers with processing properties comparable to common epoxy systems [21][22][23]. ...
... In our previous work a room temperature recycling method to recover both fibres (in the form of scrims) and matrix has been discussed [17]. Additionally, the 2nd generation composites produced using the recycled fibres showed similar structural properties to the 1st generation Elium composites [17,18]. ...
... In order to ensure uniformity with previous research [17,18], the midpoint glass transition temperature (T g ) was considered. As can be seen in Table 2, the midpoint glass transition temperature (T g ) of the modified Elium with various recyclate contents is fairly comparable to the reference matrix. ...
In this work, a closed loop recycling process is investigated, which allows polymerised bulk thermoplastic matrix (Elium 150) from production waste (also referred to as recyclate) to be reused as additive in composite manufacturing by vacuum assisted resin infusion (VARI) of virgin Elium 150 monomer. It is shown that this process can save up to 7.5 wt% of virgin material usage in each processing cycle. At the same time, the thermal stability and stiffness of the composite increases with the proportion of recyclate introduced. Contemporarily, the shear and bending properties have also been observed to improve. Gel permeation chromatography (GPC) showed that the changes observed are due to an increase in molecular weight with the recyclate content. In particular, a correlation between the molecular weight and the shear properties of the composite was discovered using single fibre push-out tests.
... In addition, this reported process offers a high potential for industrial applicability, as it requires only a minimum energy input with good scale-up possibility. In our previous study [36], the influence of temperature was investigated as well as the solvent ratio and dissolution time were optimized to achieve the highest possible matrix recovery with a minimal damage to the preform and minimum energy consumption. ...
... The matrix can also be recovered by evaporating the acetone. In contrast to our results on a smaller scale [36], further process optimization and upscaling to the laminates seemed to increase the recovery of the matrix significantly, Fig. 1. With the exception of a few fibres at the edge of the scrim -which were unavoidably displaced during the recycling process, the recovered preform was entirely intact and could be reused as it is. ...
... The thermogravimetric analysis in contrast shows a slight reduction in the thermal stability of the matrix after recycling, when referring to the 95% threshold (onset of degradation, Td) [41]. However, this reduction is noticeably lower compared to the reduction without vacuum drying of the matrix [36]. Moreover, the shoulder observed between 100°C and 200°C as a consequence of absorbed acetone during dissolution [60][61][62] (explained in our previous work [36]) is no longer visible. ...
Closed-loop room temperature recycling of Elium CFRPs and its influence on the 2nd generation composite properties This research work presents a recycling methodology for carbon fibre composites processed with a novel room temperature infusible and curable thermoplastic matrix ELIUM 150 from Arkema. Herein we demonstrate that by dissolving the composites in acetone at room temperature it is possible to separate the matrix from the fibres and to reuse both the matrix and the fibres in form of scrim (preform). A comparison of the thermomechanical, thermal and mechanical properties of the composites shows only marginal performance changes in bulk properties due to the proposed recycling strategy.
... Arkema has developed this new thermoplastic resin, with similar mechanical characteristics of thermoset resins and with the advantage of recyclability. Several works with Elium® have been developed for recycling process of fibers and thermoplastic resin [10] , [11] and [12]. At [12] two 13 m length WT blades were manufactured with both thermoset and thermoplastic resins, and comparison results have been successful. ...
The use of thermoplastic resins instead of thermoset ones in wind turbine blade manufacturing is being investigated and validated in a global scale due to some theoretical improvements such as costs saving during production, shorter cycle’s time and a better circular recovery of the raw materials at the End of Life. The initial objective of this paper was to manufacture and test a small wind turbine blade (SWTB) glass fiber-reinforced thermoplastic (GFRT) resin composites, recycle it, and use the products obtained from the recycling process (fibers and resin) to remanufacture a new thermoplastic SWTB. But loss of fibers higher than estimated during the recycling process made to get away from the original aim of testing both blades (1 st and 2 nd recyclable blades). At least, some lessons learned were obtained to improve future developments. Nevertheless, this study provides an example of how to recycle a small WT blade and to remanufacture it using the same raw materials.
... Moreover, the authors estimated the energy cost and analysed the presented methods economically. According to a previous article, Gebhardt et al. [16][17][18] proposed a recycling strategy that enables the recovery of undamaged continuous fibres in the form of scrims and up to 81% of the Elium® matrix. Conducted tests proved that Elium®, epoxy, urethane acrylate and vinylester matrixes can be successfully used with recycled fibres without a significant drop in mechanical properties. ...
Carbon fibre-reinforced polymers (CFRPs) are commonly used in aviation, automotive and renewable energy markets, which are constantly growing. Increasing the production of composite parts leads to increased waste production and a future increase in end-of-life components. To improve the recyclability of CFRPs, new materials that fit in with the idea of a circular economy should be used as a composite matrix. One such material is a commercially available thermoplastic liquid resin, Elium® (Arkema, France). In this work, the authors investigated how the mechanical recycling process affects the properties of thermoplastic-based carbon fibre composites. CFRPs with neat Elium® resin and resin modified with 0.02 wt.% single-walled carbon nanotubes or 0.02 wt.% multi-walled carbon nanotubes were manufactured using the resin infusion process. Afterwards, prepared laminates were mechanically ground, and a new set of composites was manufactured by thermopressing. The microstructure, mechanical, thermal and electrical properties were investigated for both sets of composites. The results showed that mechanical grinding and thermopressing processes lead to a significant increase in the electrical conductivity of composites. Additionally, a sharp decrease in all mechanical properties was observed.
... In the works by Tschentscher et al. [12] and Gebhardt et al. [13], these latter solvents were also used to recycle CFRP based on Elium ® 150 resin involving specimens of 200 mm × 180 mm. These latter were placed in a closed container with a selected solvent (acetone, acetophenone, ethyl acetate, or xylene). ...
The objective of this work was to compare the material recovered from different chemical recycling methodologies for thermoplastic acrylate-based composites reinforced by basalt fabrics and manufactured by vacuum infusion. Recycling was done via chemical dissolution with a preselected adapted solvent. The main goal of the study was to recover undamaged basalt fabrics in order to reuse them as reinforcements for “second-generation” composites. Two protocols were compared. The first one is based on an ultrasound technique, the second one on mechanical stirring. Dissolution kinetics as well as residual resin percentages were evaluated. Several parameters such as dissolution duration, dissolution temperature, and solvent/composite ratio were also studied. Recycled fabrics were characterized through SEM observations. Mechanical and thermomechanical properties of second-generation composites were determined and compared to those of virgin composites (called “first-generation” composites). The results show that the dissolution protocol using a mechanical stirring is more adapted to recover undamaged fabrics with no residual resin on their surface. Moreover, corresponding second-generation composites display equivalent mechanical properties than first generation ones.
In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone. Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease in viscosity (around 50%) which may promote a better dispersion of nanofillers.
Thermoanalytical investigations TGA/DTG/DSC of polyamide–imide enamel after thermal ageing have been presented. The lifetimes
at 260, 270, 280, 290, 300 °C were determined. The thermograms of the enamels after attaining of their lifetimes much depend
on the ageing temperature. The temperatures of 5% loss of mass that much increase after thermal ageing appear the most sensitive
indicator of ageing rate. The residue of mass at 800 °C increases after ageing, even to 27%, due to diffusion of copper ions
from the conductor into enamel during annealing. The copper contents in aged coatings could be also an indicator of ageing
rate.
Thermoplastic resin systems have long been discussed for use in large-scale composite parts but have yet to be exploited by the energy industry. The use of these resins versus their thermosetting counterparts can potentially introduce cost savings due to non-heated tooling, shorter manufacturing cycle times, and recovery of raw materials from the retired part. Because composite parts have high embedded energy, recovery of their constituent materials can provide substantial economic benefit. This study determines the feasibility of recycling composite wind turbine blade components that are fabricated with glass fiber reinforced Elium® thermoplastic resin. Several experiments are conducted to tabulate important material properties that are relevant to recycling, including thermal degradation, grinding, and dissolution of the polymer matrix to recover the constituent materials. Dissolution, which is a process unique to thermoplastic matrices, allows recovery of both the polymer matrix and full-length glass fibers, which maintain their stiffness (190 N/(mm g)) and strength (160 N/g) through the recovery process. Injection molded regrind material is stiffer (12 GPa compared to 10 GPa) and stronger (150 MPa compared to 84 MPa) than virgin material that had shorter fibers. An economic analysis of the technical data shows that recycling thermoplastic–glass fiber composites via dissolution into their constituent parts is commercially feasible under certain conditions. This analysis concludes that 50% of the glass fiber must be recovered and resold for a price of 2.50/kg.
GlaxoSmithKline (GSK) has previously reported on the development of a GSK solvent guide, the incorporation of lifecycle impact and the expansion of the guide including a customisable version intended for posting in different business areas. This guide has recently been enhanced by: (1) adding 44 additional solvents, many of which have literature claims to be "green"; (2) adjusting the way in which multiple health, environment, safety, and waste categories are combined to reach a single composite score and colour assignment; (3) updating the data behind all scores, especially toxicology and health hazard assessment, and revising the methodology to reflect current guidelines and data. The full methodology behind this work is hereby shared. The new GSK Solvent Sustainability Guide enables GSK scientists to objectively assess solvents. It facilitates both comparison of individual sustainability criteria, and a composite score and colour for rank ordering, incorporating multiple facets of sustainability.
Values are deduced for the interaction parameter χ for polymethyl methacrylate, polystyrene, and polyvinyl chloride systems by an application of the Fox-Flory theory to the viscosities of a polymer fraction in a suitable range of solvents. Analysis of these values as in part 1 leads to the assignment of cohesive energy densities for the polymers. For natural and butyl rubbers it is shown that the analysis of viscosity and swelling measurements lead to identical values of cohesive energy density.
Es wird eine Apparatur zur Messung der Auflösungsgeschwindigkeit von Polymeren beschrieben. Eine Probe in Tablettenform wird in ein thermokonstantes Gefäß mit Lösungsmittel gebracht. Ein Rührer bringt die aufgelöste Substanz zu einem Refraktometer, welches die Konzentrationszunahme mißt.
Der Vorgang wird mit dem 2. F ICK schen Gesetz vorerst mit Hilfe des Konzentrationsgradienten untersucht, eine Formel mit dem Gradienten des chemischen Potentials wird angedeutet. Die Auflösungsgeschwindigkeit, ausgedrückt durch die Eindringgeschwindigkeit des Lösungsmittels ⋅ [cm sec ⁻¹ ] im stationären Zustand, ist dem mittleren Eigendiffusionskoeffizienten des Lösungsmittels D̄ LM direkt und der gequollenen Schicht an der Oberfläche der Probe der Dicke δ umgekehrt proportional:
Die Temperaturabhängigkeit der Auflösung folgt der Beziehung bei einem Polystyrol (M = 32000) in Toluol ist
Solubility of polymethyl methacrylate in 12 organic solvents at 30–70°C was studied.
To reduce the environmental burden of polymer processing, the use of non-toxic solvents is desirable. In this regard, the improved solubility of poly(methyl methacrylate) (PMMA) in ethanol/water solvent mixtures is very appealing. In this contribution, detailed investigations on the solubility of PMMA in alcohol/water solvent mixtures are reported based on turbidimetry measurements. PMMA revealed upper critical solution temperature transitions in pure ethanol and ethanol/water mixtures. However, around 80 wt-% ethanol content a solubility maximum was observed for PMMA as indicated by a decrease in the transition temperature. Moreover, the transition temperatures increased with increasing PMMA molar mass as well as increasing polymer concentration. Careful analysis of both heating and cooling turbidity curves revealed a peculiar hysteresis behaviour with a higher precipitation temperature compared with dissolution with less than 60 wt-% or more than 90 wt-% ethanol in water and a reverse hysteresis behaviour at intermediate ethanol fractions. Finally, the transfer of poly(styrene)-block-poly(methyl methacrylate) block copolymer micelles from the optimal solvent, i.e. aqueous 80 wt-% ethanol, to almost pure water and ethanol is demonstrated.
Three different PAN based carbon fibres (Toray T600S, T700S and Tenax STS5631) were recycled from epoxy resin/carbon fibre composites using supercritical n-propanol. The recycled carbon fibres were characterised using single fibre tensile tests, SEM, XPS and micro-droplet test. The tensile strength and modulus of the recycled carbon fibre was very similar to the corresponding as-received carbon fibres. However, the surface oxygen concentration decreased significantly, which caused a reduction of the interfacial shear strength with epoxy resin.
Acrylic acid modified melamine resin (AM) was synthesized and used as a curing agent, in different compositions (10–40 wt.%), for DGEBA-epoxy resin (EAM). EAM resins were applied on mild steel strips of standard size to study their coating properties. The structures of AM and EAM were established by IR and spectroscopies. The physico-mechanical and anticorrosive behavior of these coatings was evaluated by standard methods. The solubility of AM was determined in various organic solvents at room temperature. TGA and DSC techniques were used to analyze the thermal properties and curing aspects of the resin. The sample with 30 wt.% loading of AM (EAM-30), among all EAM resins gave better physico-mechanical and corrosion resistance performance under various corrosive media. The acrylic-melamine modified DGEBA-epoxy coatings were compared with the reported DGEBA-polyamide coating system. It was found that EAM-30 exhibited better anticorrosive properties than the reported DGEBA-polyamide coating system.