Beating of hemp bast fibres: an examination of a hydro-mechanical treatment on chemical, structural, and nanomechanical property evolutions

In this study, a gradually increased hydro-mechanical treatments duration were applied to native hemp bast fibres with a traditional pulp and paper beating device (laboratory Valley beater). There is often a trade-off between the treatment applied to the fibres and the effect on their integrity. The multimodal analysis provided an understanding of the beating impact on the fibres at multiple scales and the experimental design made it possible to distinguish the effects of hydro- and hydro-mechanical treatment. Porosity analyses showed that beating treatment doubled the macroporosity and possibly reduced nanoporosity between the cellulose microfibrils. The beating irregularly extracted the amorphous components known to be preferentially located in the middle lamellae and the primary cell walls rather than in the secondary walls, the overall increasing the crystallinity of cellulose from 49.3 % to 59.1 %, but a non-significant change in the indentation moduli of the cell wall was observed. In addition, beating treatments with two distinct mechanical severities showed a disorganization of the cellulose conformation, which significant dropped the indention moduli by 11.2 GPa and 8.4 GPa for 10 and 20 minutes of Valley beater hydro-mechanical treatment, respectively, compared to hydro-treated hemp fibres (16.6 GPa). Pearson’s correlation coefficients between physicochemical features and the final indentation moduli were calculated. Strong positive correlations were highlighted between the cellulose crystallinity and rhamnose, galactose and mannose as non-cellulosic polysaccharide components of the cell wall

Sodium sulfate crystallisation monitoring using IR Thermography

In this work, the evaporation of sodium sulfate droplets with different concentrations and at different temperatures were studied using infrared thermography (IRT). IRT allows to detect the evaporation evolution, the crystal growth and for the first time, to observe in vivo the heat release related to sodium sulfate crystallisation. A detailed study revealed that dendritic Thenardite III crystals appeared at the edge of all the crystallised droplets, though they showed a fast increase of temperature related to crystallisation only when a hydrated phase crystallised also from the droplet. The observation of the heat of crystallisation is thus directly related to the supersaturation of the droplet and consequently to temperature. In addition, IRT detection is circumscribed by the location of crystallisation. The heat can be observed and measured only when the crystallisation occurs in the interface solution – air

Microstructural evolution of granitic stones exposed to different thermal regimes analysed by infrared thermography.

International audienceDetailed knowledge of the behaviour of rocks under thermal stress is essential in a variety of fields such as the exploitation of oil and mineral resources, the geothermal sector, the storage of radioactive liquid waste, or even CO2 capture and storage.Granites are widely studied and exploited in these fields, and they show different reactions to high-temperature and thermal cycles due mainly to their high mineralogical and textural heterogeneity. One of the features that influences the most the thermal response is the porosity.The objective of this study is to evaluate the influence of porosity when these rocks are exposed to different thermal treatments. For that purpose, experiments were carried out on four granitoids selected by their similar crystal size, but with variable mineral proportion and porosity values, ranging from 1 to 6%. Two kinds of tests were performed: i) progressive heating cycles from 90 °C to 130 °C to determine the critical threshold for thermal damage; ii) thermal fatigue with cycles of heating-cooling up to 200 °C.The porosity and the water transport phenomena of the samples were characterised before and after each cycle by the monitoring of capillary water uptake coupled with infrared thermography. This technique allowed to follow the capillary fringe migration during the test and the evolution of the cooling rate index. The direct assessment of the damage was carried out by mercury injection porosimetry, optical polarising microscopy, and scanning electron microscopy.The combination of all the results permitted to establish a link between the evolution of temperature and the modification of porous networks in granitoids. Microcracks appeared distinctly at a temperature between 90 °C to 130 °C for high porosity granitoids whose Quartz/Feldspar ratio was close to 1. For higher temperatures, the low porosity granitoids develop microcracks from the first heating cycle. The porosity then showed a stronger impact on thermal behaviour than the effect of the mineralogy. The results obtained from infrared thermography allowed to detect the strong variations in the microstructure

Estimation de l’efficacité et de la durabilité par vieillissement naturel des produits protecteurs de la pierre : le programme HYBRIPROTECH

Les monuments en pierre ont traversé les siècles et sont les témoins de l’Histoire. S’ils nous paraissent éternels, ils n’en subissent pas moins des dégradations qu’il faut prendre en compte et y remédier afin de les préserver. La détérioration du bâti est un phénomène naturel et irréversible mais la révolution industrielle et toute la pollution chimique qu’elle a engendrée ont singulièrement accéléré le processus. La restauration des monuments est inévitable mais coûteuse. Elle peut aller d’un simple nettoyage des pierres jusqu’à leur remplacement lorsque les dommages sont trop importants. Afin de ralentir l’altération des pierres, de nombreux produits existent en tant que protecteurs de la pierre, ils ont donc un effet préventif. Dans le cadre du projet HYBRIPROTECH (programme Interreg IV), une collaboration franco-belge tente de mettre au point un produit préventif plus respectueux de l’environnement et aussi efficace et durable que les produits existant actuellement. Un test de vieillissement naturel de la pierre a été mis en place pendant deux ans pour connaître l’efficacité et la durabilité réelles des produits utilisés dans les restaurations. Au cours de ce test, des échantillons traités par deux hydrofuges et un biocide photocatalytique subissent l’effet du temps et de l’environnement. Des d’échantillons sont prélevés tous les six mois sur lesquels des analyses de la couleur, de la teneur en chlorophylle et d’hydrophobicité permettent de quantifier l’évolution de l’efficacité des produits. À l’issue du premier prélèvement, les résultats des analyses montrent un développement des micro-organismes après six mois d’exposition aux intempéries

Simulation of acid rain weathering effect on natural and artificial carbonate stones

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Decellularization of Wharton’s Jelly Increases Its Bioactivity and Antibacterial Properties

International audienceThe field of regenerative medicine has recently seen an emerging trend toward decellularized extracellular matrix (ECM) as a biological scaffold for stem cell-delivery. Human umbilical cord represents a valuable opportunity from both technical and ethical point of view to obtain allogenic ECM. Herein, we established a protocol, allowing the full removal of cell membranes and nuclei moieties from Wharton’s jelly (WJ) tissue. No alterations in the ECM components ( i.e., collagen, GAG content, and growth factors), physical ( i.e., porosity and swelling) and mechanical ( i.e., linear tensile modulus) properties were noticed following WJ processing. Furthermore, no effect of the tissue processing on macromolecules and growth factors retention was observed, assuring thus a suitable bioactive matrix for cell maintenance upon recellularization. Based on the in vitro and in vivo biodegradability and stromal cell homing capabilities, decellularized WJ could provide an ideal substrate for stromal cells adhesion and colonization. Interestingly, the tissue processing increased the antibacterial and antiadhesive properties of WJ against Staphylococcus aureus and Staphylococcus epidermidis pathogens. Altogether, our results indicate that decellularized WJ matrix is able to limit Staphylococcus-related infections and to promote stromal cell homing, thus offering a versatile scaffold for tissue regenerative medicine