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This study describes the production of a new biobased epoxy thermoset and its use with long hemp fibres to produce high-performance composites that are totally biobased. The synthesis of BioIgenox, an epoxy resin derived from a lignin biorefinery, and its curing process have been optimised to decrease their environmental impact. The main objective of this study is to characterise the rheology and kinetics of the epoxy system with a view to optimising the composite manufacturing process. Thus, the epoxy resin/hardener system was chosen considering the constraints imposed by the implementation of composites reinforced with plant fibres. The viscosity of the chosen mixture shows the compatibility of the formulation with the traditional implementation processes of the composites. In addition, unlike BPA-a precursor of diglycidyl ether of bisphenol A (DGEBA) epoxy resin-BioIgenox and its precursor do not have endocrine disrupting activities. The neat polymer and its unidirectional hemp fibre composite are characterised using three-point bending tests. Results measured for the fully biobased epoxy polymer show a bending modulus, a bending strength, a maximum strain at failure and a T g of, respectively, 3.1 GPa, 55 MPa, 1.82% and 120 °C. These values are slightly weaker than those of the DGEBA-based epoxy material. It was also observed that the incorporation of fibres into the fully biobased epoxy system induces a decrease in the damping peak and a shift towards higher temperatures. These results point out the effective stress transfers between the hemp fibres and the fully biobased epoxy system. The high mechanical properties and softening temperature measured in this work with a fully biobased epoxy system make this type of composite a very promising sustainable material for transport and lightweight engineering applications.

Epoxy resin thermosets (ERTs) are an important class of polymeric materials. However, owing to their highly cross-linked nature, they suffer from poor recyclability, which contributes to an unacceptable level of environmental pollution. There is a clear need for the design of inherently recyclable ERTs that are based on renewable resources. We present the synthesis and closed-loop recycling of a fully lignocellulose-derivable epoxy resin (DGF/MBCA), prepared from dimethyl ester of 2,5-furandicarboxylic acid (DMFD), 4,4'-methylenebis(cyclohexylamine) (MBCA), and glycidol, which displays excellent thermomechanical properties (a glass transition temperature of 170°C, and a storage modulus at 25°C of 1.2 gigapascals). Notably, the material undergoes methanolysis in the absence of any catalyst, regenerating 90% of the original DMFD. The diamine MBCA and glycidol can subsequently be reformed by acetolysis. Application and recycling of DGF/MBCA in glass and plant fiber composites are demonstrated.

The stinging nettle Urtica dioica L. is a perennial crop with low fertilizer and pesticide requirements, well adapted to a wide range of environmental conditions. It has been successfully grown in most European climatic zones while also promoting local flora and fauna diversity. The cultivation of nettle could help meet the strong increase in demand for raw materials based on plant fibers as a substitute for artificial fibers in sectors as diverse as the textile and automotive industries. In the present review, we present a historical perspective of selection, harvest, and fiber processing features where the state of the art of nettle varietal selection is detailed. A synthesis of the general knowledge about its biology, adaptability, and genetics constituents, highlighting gaps in our current knowledge on interactions with other organisms, is provided. We further addressed cultivation and processing features, putting a special emphasis on harvesting systems and fiber extraction processes to improve fiber yield and quality. Various uses in industrial processes and notably for the restoration of marginal lands and avenues of future research on this high-value multi-use plant for the global fiber market are described.

Despite the increased use of hemp fiber, negligible attention has been given to upgrade the hemp hurd, which constitutes up to 70 wt % of the hemp stalk and is currently considered a low-value byproduct. In this work, valorization of hemp hurd was performed by reductive catalytic fractionation (RCF) in the presence of a metal catalyst. We found an unexpectedly high yield of monophenolic compounds (38.3 wt %) corresponding to above 95% of the theoretical maximum yield. The high yield is explained by both a thin cell wall and high S-lignin content. In addition, organosolv pulping was performed to generate a pulp that was bleached to produce dissolving-grade pulp suitable for textile fiber production (viscosity, 898 mL/g; ISO-brightness, 90.2%) and nanocellulose. Thus, we have demonstrated a novel value chain from a low-value side stream of hemp fiber manufacture that has the potential to increase textile fiber production with 100% yield and also give bio-oil for green chemicals., Competing Interests: The authors declare the following competing financial interest(s): J.S.M.S. is founder of RenFuel, a company that valorizes lignin. No other authors have any conflict of interests., (© 2021 The Authors. Published by American Chemical Society.)

Flax has a long and fascinating history. This plant was domesticated around 8,000 BCE 1 in the Fertile Crescent area 2 , first for its seeds and then for its fibres 1,3 . Although its uses existed long before domestication, residues of flax yarn dated 30,000 years ago have been found in the Caucasus area 4 . However, Ancient Egypt laid the foundations for the cultivation of flax as a textile fibre crop 5 . Today flax fibres are used in high-value textiles and in natural actuators 6 or reinforcements in composite materials 7 . Flax is therefore a bridge between ages and civilizations. For several decades, the development of non- or micro-destructive analysis techniques has led to numerous works on the conservation of ancient textiles. Non-destructive methods, such as optical microscopy 8 or vibrational techniques 9,10 , have been largely used to investigate archaeological textiles, principally to evaluate their degradation mechanisms and state of conservation. Vibrational spectroscopy studies can now benefit from synchrotron radiation 11 and X-ray diffraction measurement in the archaeometric study of historical textiles 12,13 . Conservation of mechanical performance and the ultrastructural differences between ancient and modern flax varieties have not been examined thus far. Here we examine the morphological, ultrastructural and mechanical characteristics of a yarn from an Egyptian mortuary linen dating from the early Middle Kingdom (Eleventh Dynasty, ca. 2033-1963 BCE) and compare them with a modern flax yarn to assess the quality and durability of ancient flax fibres and relate these to their processing methods. Advanced microscopy techniques, such as nano-tomography, multiphoton excitation microscopy and atomic force microscopy were used. Our findings reveal the cultural know-how of this ancient civilization in producing high-fineness fibres, as well as the exceptional durability of flax, which is sometimes questioned, demonstrating their potential as reinforcements in high-technology composites., (© 2021. The Author(s), under exclusive licence to Springer Nature Limited.)

Shifting from petrochemical feedstocks to renewable resources can address some of the environmental issues associated with petrochemical extraction and make plastics production sustainable. Therefore, there is a growing interest in selective methods for transforming abundant renewable feedstocks into monomers suitable for polymer production. Reported herein are one-pot catalytic systems, that are active, productive, and selective under mild conditions for the synthesis of copolymers from renewable materials. Each system allows for anhydride formation, alcohol acylation and/or acid esterification, as well as polymerization of the formed (meth)acrylates, providing direct access to a new library of unique poly(meth)acrylates., (© 2021 Wiley-VCH GmbH.)

FINEAU (2021-2024) is a trans-disciplinary research project involving French, Serbian, Italian, Portuguese and Romanian colleagues, a French agricultural cooperative and two surface-treatment industries, intending to propose chènevotte, a co-product of the hemp industry, as an adsorbent for the removal of pollutants from polycontaminated wastewater. The first objective of FINEAU was to prepare and characterize chènevotte-based materials. In this study, the impact of water washing and treatments (KOH, Na 2 CO 3 and H 3 PO 4 ) on the composition and structure of chènevotte (also called hemp shives) was evaluated using chemical analysis, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray computed nanotomography (nano-CT), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, solid state NMR spectroscopy and thermogravimetric analysis. The results showed that all these techniques are complementary and useful to characterize the structure and morphology of the samples. Before any chemical treatment, the presence of impurities with a compact unfibrillated structure on the surfaces of chènevotte samples was found. Data indicated an increase in the crystallinity index and significant changes in the chemical composition of each sample after treatment as well as in surface morphology and roughness. The most significant changes were observed in alkaline-treated samples, especially those treated with KOH.

Lignocellulosic fibers extracted from plants are considered an interesting raw material for environmentally friendly products with multiple applications. This work investigated the feasibility of using hemp- and flax-based materials in the form of felts as biosorbents for the removal of metals present in aqueous solutions. Biosorption of Al, Cd, Co, Cu, Mn, Ni and Zn from a single solution by the two lignocellulosic-based felts was examined using a batch mode. The parameters studied were initial metal concentration, adsorbent dosage, contact time, and pH. In controlled conditions, the results showed that: (i) the flax-based felt had higher biosorption capacities with respect to the metals studied than the hemp-based felt; (ii) the highest removal efficiency was always obtained for Cu ions, and the following order of Cu > Cd > Zn > Ni > Co > Al > Mn was found for both examined biosorbents; (iii) the process was rapid and 10 min were sufficient to attain the equilibrium; (iv) the efficiency improved with the increase of the adsorbent dosage; and (v) the biosorption capacities were independent of pH between 4 and 6. Based on the obtained results, it can be considered that plant-based felts are new, efficient materials for metal removal.

The present work investigates the effects of an environmentally friendly treatment based on supercritical carbon dioxide (scCO 2 ) on the interfacial adhesion of flax fibers with thermoset matrices. In particular, the influence of this green treatment on the mechanical (by single yarn tensile test), thermal (by TGA), and chemical (by FT-IR) properties of commercially available flax yarns was preliminary addressed. Results showed that scCO 2 can significantly modify the biochemical composition of flax fibers, by selectively removing lignin and hemicellulose, without altering their thermal stability and, most importantly, their mechanical properties. Single yarn fragmentation test results highlighted an increased interfacial adhesion after scCO 2 treatment, especially for the vinylester matrix, in terms of reduced debonding and critical fragment length values compared to the untreated yarns by 18.9% and 15.1%, respectively. The treatment was less effective for epoxy matrix, for which debonding and critical fragment length values were reduced to a lesser extent, by 3.4% and 3.7%, respectively., Competing Interests: The authors declare no conflict of interest.

Epoxy resin plays a key role in composite matrices and DGEBA is the major precursor used. With the aim of favouring the use of bio resources, epoxy resins can be prepared from lignin. In particular, diglycidyl ether of isoeugenol derivatives are good candidates for the replacement of DGEBA. This article presents an effective and eco-friendly way to prepare epoxy resin derived from isoeugenol (BioIgenox), making its upscale possible. BioIgenox has been totally characterized by NMR, FTIR, MS and elemental analyses. Curing of BioIgenox and camphoric anhydride with varying epoxide function/anhydride molar ratios has allowed determining an optimum ratio near 1/0.9 based on DMA and DSC analyses and swelling behaviours. This thermoset exhibits a Tg measured by DMA of 165 °C, a tensile storage modulus at 40 °C of 2.2 GPa and mean 3-point bending stiffness, strength and strain at failure of 3.2 GPa, 120 MPa and 6.6%, respectively. Transposed to BioIgenox/hexahydrophtalic anhydride, this optimized formulation gives a thermoset with a Tg determined by DMA of 140 °C and a storage modulus at 40 °C of 2.6 GPa. The thermal and mechanical properties of these two thermosets are consistent with their use as matrices for structural or semi-structural composites.

The diep-oxy monomer, C 13 H 16 O 4 { DGE-Eu ; systematic name: 2-[3-meth-oxy-4-(oxiran-2-ylmeth-oxy)benz-yl]oxirane}, was synthesized from eugenol by a three-step reaction. It consists of a 1,2,4-tris-ubstituted benzene ring substituted by diglycidyl ether, a meth-oxy group and a methyl-oxirane group. The three-membered oxirane rings are inclined to the benzene ring by 61.0 (3) and 27.9 (3)°. The methyl-ene C atom of one of the two terminal epoxide rings is positionally disordered [refined occupancy ratio = 0.69 (1):0.31 (1)]. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming layers parallel to the ab plane. The layers are linked by C-H⋯π inter-actions, forming a three-dimensional network.

Aim: This study investigated the effects of pre- and post-cooling on self-paced time-trial cycling performance and recovery of cyclists exercising under a hot and highly humid environment (29.92 °C-78.52% RH)., Methods: Ten male cyclists performed a self-paced 20-min time trial test (TT20) on a cyclo-ergometer while being cooled by a cooling vest and a refrigerating headband during the warm-up and the recovery period. Heart rate, power output, perceived exertion, thermal comfort, skin and rectal temperatures were recorded., Results: Compared to control condition (222.78 ± 47 W), a significant increase (P<0.05) in the mean power output during the TT20 (239.07 ± 45 W; +7.31%) was recorded with a significant (P<0.05) decrease in skin temperature without affecting perceived exertion, heart rate, or rectal temperature at the end of the TT20. However, pace changes occurred independently of skin or rectal temperatures variations but a significant difference (P<0.05) in the body's heat storage was observed between both conditions. This result suggests that a central programmer using body's heat storage as an input may influence self-paced time-trial performance. During the recovery period, post-cooling significantly decreased heart rate, skin and rectal temperatures, and improved significantly (P<0.05) thermal comfort., Conclusion: Therefore, in hot and humid environments, wearing a cooling vest and a refrigerating headband during warm-up improves self-paced performance, and appears to be an effective mean of reaching skin rest temperatures more rapidly during recovery.

Background/aims: Different models of reconstructed skin are available, either to provide skin wound healing when this process is deficient, or to be used as an in vitro model. Nevertheless, few studies have focused on the mechanical properties of skin equivalent. Indeed, human skin is naturally under tension. Taking into account these features, the purpose of this work was to obtain a cellularized dermal equivalent (CDE), composed of collagen and dermal fibroblasts., Methods: To counteract the natural retraction of CDE and to maintain it under tension, different biomaterials were tested. Selection criteria were biocompatibility, bioadhesion properties, ability to induce differentiation of fibroblasts into myofibroblasts and mechanical characterization, considering that of skin in vivo. These assays led to the selection of honeycomb of polyester. CDE constructed on this biomaterial was further characterized mechanically using tensile tests., Results: The results showed that mechanical features of the obtained dermal equivalent, including myofibroblasts, were similar to skin in vivo., Conclusion: The original model of dermal equivalent presented herein may be a useful tool for clinical use and as an in vitro model for toxicological/pharmacological research., (© 2011 John Wiley & Sons A/S.)

Gonzales, BR, Hagin, V, Guillot, R, Placet, V, and Groslambert, A. Effects of polyester jerseys on psycho-physiological responses during exercise in a hot and moist environment. J Strength Cond Res 25(12): 3432-3438, 2011-With the general acceptance that extreme environments have a detrimental effect on thermoregulation and human performance, the aim of this study was to investigate the influence of 3 polyester jerseys with knits of different sizes on physiological and perceptual responses in trained cyclists during exercise performed in a hot and moist environment. Ten trained male cyclists (mean ± SD, age: 29.1 ± 8 years, height: 177.12 ± 5 cm, body mass: 70.10 ± 6 kg), performed 3 tests of 15 minutes at 150 W on a calibrated home trainer by randomly wearing jerseys with small knits (SK), medium knits, and large knits (LK). While exercising, the jersey and torso skin temperatures, perceived exertion and hotness, and heart rate (HR) were continuously recorded. The major results of this study showed that perceived hotness with LK was significantly lower (p < 0.05) than with SK at minutes 10 (effect size [ES] = 1.18) and 12 (ES = 1.04) of exercise. The torso skin temperature with LK was significantly lower (p < 0.05) than with SK at minute 10 (ES = 0.84) and at minute 14 (ES = 0.81) of exercise, and the LK jersey temperature was significantly lower (p < 0.05) than with SK jerseys at minutes 12 (ES = 0.83) and 14 (ES = 0.90) of exercise. However, no significant difference was found in perceived exertion or HR. These results suggest that the use of polyester jerseys with larger knits could limit the drift of skin temperature and therefore increase the thermal comfort of cyclists during exercise performed in a hot and moist environment. Therefore, coaches are encouraged to take particular care that their athletes wear exercise-appropriate clothing in hot temperatures.

Objectives: The peroperative rupture of a collagen membrane is a potential cause of complications and loss of effectiveness. The purpose of our study was to determine experimentally the mechanical properties (Young modulus, stress-strain curve, tensile strength) of three collagen membranes used in guided bone regeneration. These properties and isotropy were compared on dry and damp samples., Methods: Standardized samples were tailored in three different membranes (Biomend Extend(®) [Zimmer Dental™], Bio-Gide(®) [Geitslich™] Neonem(®) [TBR™]) in two orthogonal orientations. They were then anchored on an ElectroForce(®) 3230 Instrument (Bose™) traction machine in a dry and wet state (soaking during 10 minutes in saline at 37°C). The strain curves were analyzed to obtain the various mechanical values., Results: No anisotropy was observed. The Biomend Extend(®) membranes were significantly more resistant in dry and damp states than others., Discussion: The mechanical properties of collagen membranes are very different from one to another. Moistening of the membranes, unavoidable in vivo, considerably alters their mechanical properties. This data should be taken into consideration when choosing a membrane., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

The aim of this study was to understand how the molecular structures of amorphous polymers influence wood viscoelastic properties. Wood from oak and spruce was subjected to hydrothermal treatments at 110 or 135 degrees C. Wood rigidity, reflected by the wood storage modulus, showed different modification patterns according to the wood species or the temperature level. Because viscoelasticity is dependent on wood amorphous polymers, modifications of lignins and noncellulosic polysaccharides were examined. Hemicellulose degradation occurred only at 135 degrees C. In contrast, lignins displayed major structural alterations even at 110 degrees C. In oak lignins, the beta-O-4 bonds were extensively degraded and wood rigidity decreased dramatically during the first hours of treatment. Spruce lignins have a lower beta-O-4 content and, relative to oak, the wood rigidity decrease due to treatment was less pronounced. Wood rigidity was restored to its initial value by prolonged treatment, probably due to the formation of condensed bonds in cell wall polymers.