Estimating the bias related to DNA recovery from hemp stems for retting microbial community investigation.

The industrial hemp plant Cannabis sativa is a source of vegetable fiber for both textiles and biocomposite applications. After harvesting, the plant stems are laid out on the ground and colonized by microorganisms (bacteria and fungi) naturally present in the soil and on the stems. By producing hydrolytic enzymes that degrade the plant wall polymers, the natural cement that binds the fiber bundles together is removed, thus facilitating their dissociation (retting process) which is required for producing high-performant fibers. To investigate temporal dynamics of retting microbial communities (density levels, diversity, and structure), a reliable protocol for extracting genomic DNA from stems is mandatory. However, very little attention has been paid to the methodological aspects of nucleic acid extraction, although they are crucial for the significance of the final result. Three protocols were selected and tested: a commercial kit (FastDNA™ Spin Kit for soil), the Gns-GII procedure, and a custom procedure from the Genosol platform. A comparative analysis was carried out on soil and two different varieties of hemp stem. The efficiency of each method was measured by evaluating both the quantity and quality of the extracted DNA and the abundance and taxonomy of bacterial and fungal populations. The Genosol protocol provides interesting yields in terms of quantity and quality of genomic DNA compared to the other two protocols. However, no major difference was observed in microbial diversity between the two extraction procedures (FastDNA™ SPIN Kit and Genosol protocol). Based on these results, the FastDNA™ SPIN kit or the Genosol procedure seems to be suitable for studying bacterial and fungal communities of the retting process. It should be noted that this work has demonstrated the importance of evaluating biases associated with DNA recovery from hemp stems. KEY POINTS: • Metagenomic DNA was successfully extracted from hemp stem samples using three different protocols. • Further evaluation was performed in terms of DNA yield and purity, abundance level, and microbial community structure. • This work exhibited the crucial importance of DNA recovery bias evaluation.

Chemical Recycling of Vacuum-Infused Thermoplastic Acrylate-Based Composites Reinforced by Basalt Fabrics.

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.

Shear and Extensional Rheology of Linear and Branched Polybutylene Succinate Blends.

The molecular architecture and rheological behavior of linear and branched polybutylene succinate blends have been investigated using size-exclusion chromatography, small-amplitude oscillatory shear and extensional rheometry, in view of their processing using cast and blown extrusion. Dynamic viscoelastic properties indicate that a higher branched polybutylene succinate amount in the blend increases the relaxation time due to an increased long-chain branching degree. Branched polybutylene succinate exhibits pronounced strain hardening under uniaxial elongation, which is known to improve processability. Under extensional flow, the 50/50 wt % blend exhibits the same behavior as linear polybutylene succinate.

New Biosourced Flame Retardant Agents Based on Gallic and Ellagic Acids for Epoxy Resins.

The aim of this work was an investigation of the ability of gallic (GA) and ellagic (EA) acids, which are phenolic compounds encountered in various plants, to act as flame retardants (FRs) for epoxy resins. In order to improve their fireproofing properties, GA and EA were treated with boric acid (to obtain gallic acid derivatives (GAD) and ellagic acid derivatives (EAD)) to introduce borate ester moieties. Thermogravimetric analysis (TGA) highlighted the good charring ability of GA and EA, which was enhanced by boration. The grafting of borate groups was also shown to increase the thermal stability of GA and EA that goes up respectively from 269 to 528 °C and from 496 to 628 °C. The phenolic-based components were then incorporated into an epoxy resin formulated from diglycidyl ether of bisphenol A (DGEBA) and isophorone diamine (IPDA) (72, 18, and 10 wt.% of DGEBA, IPDA, and GA or EA, respectively). According to differential scanning calorimetry (DSC), the glass transition temperature (Tg) of the thermosets was decreased. Its values ranged from 137 up to 108 °C after adding the phenolic-based components. A cone calorimeter was used to evaluate the burning behavior of the formulated thermosets. A significant reduction of the peak of heat release rate (pHRR) for combustion was detected. Indeed, with 10 wt.% of GA and EA, pHRR was reduced by 12 and 44%, respectively, compared to that for neat epoxy resin. GAD and EAD also induced the decrease of pHRR values by 65 and 33%, respectively. In addition, a barrier effect was observed for the resin containing GAD. These results show the important influence of the biobased phenolic compounds and their boron derivatives on the fire behavior of a partially biobased epoxy resin.

Evolution of temporal dynamic of volatile organic compounds (VOCs) and odors of hemp stem during field retting.

MAIN CONCLUSION: New non-destructive approach to evaluate the retting process was investigated. Increase of retting duration led to a decrease of VOCs emitted by plants and change of color and plant odor. The variation of VOCs and odor could be used as indicators for the degree of retting. In the hemp industry, retting is an upstream bioprocessing applied to the plants to facilitate the decortication of fibres from the central woody part of the stem. This treatment is currently carried out in an empirical way on the ground which leads to variability in the hemp stems quality, and thus to the hemp fibres quality. Therefore, controlling retting treatment is a crucial step for high-performance hemp fibre. In this study, a new approach is used to assess the retting degree by following the evolution of VOCs emitted by plants during different retting durations. Either harvest time or retting induces a change in VOCs released by plants. During plant maturity, volatile compounds emitted decreased with a factor of about 2, in relation to VOCs released at the end of flowering. Regardless of the harvest period, the majority of VOCs and odor concentrations, monitored by olfactometric analysis, decrease gradually until some of them disappear at the end of retting. Likewise, the green plant odor disappears during retting with an increase of dry plants odor and an appearance of fermented odor at the end of retting. Following the evolution of VOCs emitted by plants during retting could be a tool for farmers to improve the retting management.

How to manage biocomposites wastes end of life? A life cycle assessment approach (LCA) focused on polypropylene (PP)/wood flour and polylactic acid (PLA)/flax fibres biocomposites.

Biocomposites has gained increasing attention in recent years. The environmental impacts of end-of-life (EoL) treatments of those emerging materials should be evaluated before they are produced and installed commercially, to ensure a minimal impact of these products all along their life cycle. Life cycle assessment (LCA) was carried out to evaluate environmental impacts of the EoL treatments of wood flour (WF) reinforced polypropylene (PP/WF) and flax fibers reinforced polylactic acid (PLA/Fl). The aim was to evaluate which EoL was the most environmental friendly to manage those emerging wastes in France and to help stakeholders of the waste sectors in their decisions. The attributional LCA was realized using the methodological framework of the international standard ISO 14040:2006. The study only focuses on the EoL of the biocomposites with four scenarios: incineration, landfill, composting and recycling. Mid-point indicators were evaluated thanks to the Recipe method. Results were also normalized to the annual mean environmental impact of a European inhabitant. For both biocomposites, recycling EoL scenario presents the lowest environmental impacts except for the freshwater eutrophication impact of the PP/WF EoL. Models should be completed in the future when new data will be available. Results obtained for both biocomposites are in agreement with the European waste hierarchy. If recycling of plastic is difficult to implement, incineration would be the preferable option for the PP/WF composite, while composting would be the other choice for PLA/Fl material.

Sodium alginate adhesives as binders in wood fibers/textile waste fibers biocomposites for building insulation.

Alginate derived from seaweed is a natural polysaccharide able to form stable gel through carbohydrate functional groups largely used in the food and pharmaceutical industry. This article deals with the use of sodium alginate as an adhesive binder for wood fibres/textile waste fibres biocomposites. Several aldehyde-based crosslinking agents (glyoxal, glutaraldehyde) were compared for various wood/textile waste ratios (100/0, 50/50, 60/40, 70/30 and 0/100 in weight). The fully biomass derived composites whose properties are herewith described satisfy most of the appropriate requirements for building materials. They are insulating with a thermal conductivity in the range 0.078-0.089 W/m/K for an average density in the range 308-333 kg/m3 according to the biocomposite considered. They are semi-rigid with a maximal mechanical strength of 0.84 MPa under bending and 0.44 MPa under compression for 60/40 w/w wood/textile waste biocomposites with a glutaraldehyde crosslinking agent.

Stimuli-responsive topological change of microstructured surfaces and the resultant variations of wetting properties.

It is now well established that topological microstructures play a key role in the physical properties of surfaces. Stimulus-induced variations of topological microstructure should therefore lead to a change in the physical properties of microstructured responsive surfaces. In this paper, we demonstrate that roughness changes alter the wetting properties of responsive organic surfaces. Oriented nematic liquid crystalline elastomers (LCEs) are used to construct the microstructured surfaces via a replica molding technique. The topological microstructure of the surfaces covered with micropillars changes with temperature, due to the reversible contraction of the LCE pillars along the long axis at the nematic-to-isotropic phase transition. This is directly observed for the first time under environmental scanning electron microscopy (E-SEM). A high boiling point liquid, glycerol, is used to continuously monitor the contact angle change with temperature. The glycerol contact angle of the microstructured surfaces covered with small pillars decreases from 118° at room temperature to 80° at 140 °C, corresponding to a transition from Cassie state to Wenzel state.

Micron-sized main-chain liquid crystalline elastomer actuators with ultralarge amplitude contractions.

Responsive surfaces composed of cylindrical or square micrometer-sized thermoresponsive pillars made of thiol-ene nematic main-chain liquid crystalline elastomers (LCEs) are produced by replica molding. The individual pillars behave as microactuators, showing ultralarge and reversible contractions of around 300-400% at the nematic to isotropic phase transition. The nematic main-chain LCE microactuators described here present contractions as large as the best macroscopic systems reported in the literature. Moreover, the contraction observed for this new system outperforms the best values already reported for other LCE microsystems.