Shear Refinement of Formaldehyde-Free Corn Starch and Mimosa Tannin (Acacia mearnsii) Wood Adhesives

The aim of this work was to reduce the viscosity of formaldehyde-free corn starch–mimosa tannin wood adhesives, without adversely affecting the mechanical properties of the product. The reduction of viscosity was achieved using shear refinement. The study focused on the physical phenomena before cross-linking of the wood adhesive. The physical (rheological characterization) and mechanical (bond strength) properties of formaldehyde-free corn starch and mimosa tannin wood adhesives were measured. The results showed that the shear refinement (290 rpm and 5 min, optimal conditions) reduced the viscosity of the corn starch–mimosa tannin wood adhesives (from 100 000 to 458 Pa s) with the advantage of being stable over time. Mechanical tests showed that the shear refinement did not influence the mechanical properties of corn starch–mimosa tannin wood adhesives

New Trends in Clay-Based Nanohybrid Applications: Essential Oil Encapsulation Strategies to Improve Their Biological Activity

Essential oils (EOs) are used in medicinal, pharmaceutical, cosmetic, agricultural, and food industries thanks to their key properties and multiple benefits. Several techniques and embedding materials are used to nanoencapsulate EOs, in order to keep them from environmental conditions and boost their bioefficiency by controlled release. In recent years, the interest for clay nanoparticles as nanoencapsulation materials for EOs is increasing owing to their abundance in nature, low cost, inertness, and special structure. Thus, this chapter focuses on highlighting data and contributions dealing with EOs incorporation into nanoclay particles, their current applications and nanohybrid formation benefits on the stability, bioavailability, and sustained release of EOs. An overview about nanoclays used for EOs nanoencapsulation is highlighted in the beginning of this chapter followed by a brief description of EOs’ chemical composition and properties

Insights into the Evolution of Multicellularity from the Sea Lettuce Genome

We report here the 98.5 Mbp haploid genome (12,924 protein coding genes) of Ulva mutabilis, a ubiquitous and iconic representative of the Ulvophyceae or green seaweeds. Ulva’s rapid and abundant growth makes it a key contributor to coastal biogeochemical cycles; its role in marine sulfur cycles is particularly important because it produces high levels of dimethylsulfoniopropionate (DMSP), the main precursor of volatile dimethyl sulfide (DMS). Rapid growth makes Ulva attractive biomass feedstock but also increasingly a driver of nuisance “green tides.” Ulvophytes are key to understanding the evolution of multicellularity in the green lineage, and Ulva morphogenesis is dependent on bacterial signals, making it an important species with which to study cross-kingdom communication. Our sequenced genome informs these aspects of ulvophyte cell biology, physiology, and ecology. Gene family expansions associated with multicellularity are distinct from those of freshwater algae. Candidate genes, including some that arose following horizontal gene transfer from chromalveolates, are present for the transport and metabolism of DMSP. The Ulva genome offers, therefore, new opportunities to understand coastal and marine ecosystems and the fundamental evolution of the green lineage

Développement de bio-composites à base de fibres végétales et de colles écologiques

L intégration des fibres naturelles cellulosiques de plantes annuelles ou de résidus agricoles ou agro-industriels dans l élaboration de matériaux de structures composites et le développement de nouveaux liants biosourcés sont aujourd hui un domaine de recherche d intérêt croissant. La thèse s'est déroulée dans le cadre du programme Eco-panneaux , dont les deux objectifs principaux furent tout d'abord de valoriser les fibres végétales d origine tunisienne comme l alfa, le jonc et les folioles de palme et ensuite d'évaluer le potentiel d'espèces végétales tunisiennes dont les écorces sont riches en tannins (fruit de grenade, racines du sumac et tronc de pin d Alep). Les études de caractérisation des fibres ont montré que leurs masses volumiques sont inférieures à 1. Le calcul du point de saturation des fibres (FSP) montre des valeurs majoritairement comprises entre 60 et 100 %. Nous avons également pu caractériser la cinétique d'imprégnation d'eau pour chacune des fibres. L imprégnation se stabilise après 24 h d immersion. Riches en minéraux (concentrations supérieures à 1 %), les fibres ont montré des teneurs en cellulose, en lignines et en hémicellulose comparables à celles généralement rencontrées avec les fibres de bois. L analyse thermogravimétrique (ATG) a permis de constater que les matrices végétales étudiées sont thermiquement stables pour des températures inférieures à 200C. Le dosage colorimétrique pour étudier la composition en polyphénols des matrices tannifères, l analyse infrarouge et l étude structurale de l extrait des tanins, ainsi que le calcul du Stiasny number , montrent la forte teneur de l écorce de grenade en tanins hydrolysables et la richesse des écorces du tronc de pin d Alep et des racines du sumac en tanins condensés. L étude des propriétés thermiques des extraits de tanins par ATG montre que les tanins de pin d Alep et du sumac sont thermiquement plus stables que ceux de la grenade. La colle formulée à partir d hexamine et de tanins de pin d Alep présente un module d élasticité élevé. Alors que la colle à base de tanins de grenade forme le réseau le moins dense. Ces résultats ont été confirmés par l étude de la résistance au cisaillement. L'étude réalisée sur les composites fibres-plâtre (mise en œuvre et caractérisation physico mécanique des composites) a montré que les fibres locales pourraient constituer une alternative aux fibres d'importation utilisées actuellement. Une première caractérisation de la conductivité thermique des panneaux isolants élaborés à partir des fibres locales et de colles de tanins montre une conductivité thermique moyenne de 0,106w/K.m.The integration of natural cellulosic fibers from annual plants and agricultural residues and agro-industrial materials in the development of composite structures and the development of new bio-based adhesives, are now a research field with growing interest. The thesis was conducted within the framework of "Eco-panels" program, which its two main objectives were firstly, to enhance plant fibers of Tunisian origin as alfa, rush and palm leaflets and then to evaluate the potential of Tunisian plant species whose bark is rich in tannins (pomegranate fruit, sumac roots and Aleppo pine trunk). The characterization studies of fibers showed that their densities are less than 1. The calculation of the fiber saturation point (FSP) shows values mostly between 60 and 100 %. We were also able to characterize the impregnation kinetics of water for each of these fibers. The impregnation stabilizes after 24 h of immersion. Rich in minerals (concentrations greater than 1 %), the fibers showed levels of cellulose, lignin and hemicellulose comparable to those generally encountered with wood fibers. The thermogravimetric analysis (TGA) shows that the plant matrices are thermally stable for temperatures below 200 C. The colorimetric assay of the polyphenolic composition of tanniferous matrices, the infrared analysis and the structural study of the tannins extract, as well as the calculation of "Stiasny number" show the high content in hydrolysable tannins for pomegranate barks and richness of Aleppo pine trunk barks and sumac roots barks in condensed tannins. The study by TGA of the thermal properties of tannins extracts shows that Aleppo pine and sumac tannins are thermally more stable than those of pomegranate. The formulation made from hexamine and Aleppo pine tannins has the greatest elasticity modulus. While the formulation prepared from pomegranate tannins forms the least dense network. These results were confirmed by the study of the shear strength. The study conducted on fiber-plaster composites (implementation and physico-mechanical characterization of composites) showed that local fiber could be an alternative to imported fibers used currently. A first characterization of the thermal conductivity of insulation panels made from local plant fibers and tannins adhesives shows an average conductivity of 0,106 W / Km.PAU-BU Sciences (644452103) / SudocSudocFranceF

Cornstarch and tannin in phenol-formaldehyde resins for plywood production

cited By 59International audienceThe aim of this work is to demonstrate the performances of cornstarch-quebracho tannin-based resins designed as adhesive in the plywood production. In this way, the cornstarch and quebracho tannin was introduced in the classic adhesive formulation in order to supply a part of phenol-formaldehyde (PF). The physical properties (rheological characterization, thermogravimetric analysis and solid phase 13C NMR analysis) of the formulated resins were measured. In order to evaluate the mechanical performances of optimal cornstarch-quebracho tannin-based resins, plywood panels were produced and mechanical properties were investigated. These mechanical properties included tensile strength, wood failure and 3-point bending strength. The performance of these panels is comparable to those of plywood panels commercial PF made. The results showed that plywood panels bonded with cornstarch-quebracho tannin-PF resins (15:5:80, w/w/w) exhibited better mechanical properties than plywood panels commercial PF made. The introduction of small proportions of cornstarch and quebracho tannin in PF resins contributes to the improvement of the boiling water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with cornstarch-quebracho tannin-PF were lower to those obtained from panels bonded with control PF. Solid state CPMAS NMR spectra indicates that no reaction at all between PF resins and cornstarch and quebracho tannin. Even when reaction does evidently not occur, the addition of cornstarch and quebracho tannin improves markedly the water resistance of PF resins. © 2009 Elsevier B.V

Valorization of Tunisian alfa fibres and sumac tannins for the elaboration of biodegradable insulating panels

Alfa leaves are important renewable raw materials in Tunisia where they are used basically in handcrafts and paper industry. Sumac is also an abundant species in Tunisia known for its high tannin content and is basically used in traditional medicine. To valorize these natural resources, we studied, for the first time, the possibility of making insulating panels based on alfa fibres and sumac tannins based adhesive. Firstly, alfa leaves were treated with an alkali solution as it is one of the standard procedures commonly used in the paper industry to extract cellulosic fibres. Mercerization effects were studied by characterizing fibres thermal properties and fibres surface morphology. Secondly, the sumac tannin based resin was formulated and characterized. Finally, the insulating panel was elaborated and characterized by determining its thermal conductivity. The thermal gravimetric analysis results show improvement in the thermal stability of fibres after alkali treatment. Environmental Scanning Electron Microscopy showed changes on treated alfa surface which could promote the fibre-matrix adhesion. The reactivity of sumac tannins to formaldehyde test (Stiasny number) showed the possible use of sumac tannins in wood adhesive formulation. Thermomechanical analysis and strength analysis of sumac tannin/hexamin based resin highlighted acceptable bonding properties. The thermal conductivity measurement showed an average value equal to 0.110 W/m K

Evaluation of decay resistance of wood products made from borax-impregnated wood and bonded with a formaldehyde-free cornstarch and tannin adhesive

• At present, the production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as phenol-formaldehyde (PF) resins and urea- formaldehyde (UF) resins, which are non-renewable and therefore ultimately limited in supply. • This paper concerns the decay resistance of wood products bonded with a new, environment-friendly adhesive derived from abundant and renewable cornstarch and tannin. To improve the total resistance of the composite against both Coriolus versicolor and Coniophora puteana rot fungi, borax (di-sodium tetraborate) was added in proportions of 0.5%, 1% and 2% (w/w) to the cornstarch-tannin adhesives. • The results show that increasing the concentration of borax in the adhesive decreased the mechanical properties of the composite. The best way to avoid this problem was to use wood impregnated with borax. • Biodegradation studies were conducted on new composites, first without any treatment, followed by borax at 0.5% aqueous solution treatment. The results show that wood impregnated with borax, in the presence of tannin and sodium hydroxide in the adhesive improves the total resistance of the wood composite against both Coriolus versicolor and Coniophora puteana rot fungi.Évaluation de la durabilité des produits en bois imprégnés avec du borax et collés avec un adhésif naturel à base d'amidon de maïs et de tannin. • Actuellement, la production des composites à base de bois nécessite l'utilisation d'adhésifs d'origine pétrochimique et à base de formaldéhyde, tels que le phénol-formaldéhyde (PF) et l'urée-formaldéhyde (UF), qui sont non renouvelables et limités dans l'approvisionnement. • Ce travail a pour objectif d'étudier la durabilité du bois collé avec une nouvelle colle naturelle à base d'amidon et tannin. Pour améliorer la résistance des composites vis-à-vis des deux types principaux de dégradation fongique, Coriolus versicolor et Coniophora puteana, nous avons ajouté à l'adhésif, différentes concentrations de borax (di-sodium tetraborate) 0,5 %, 1 % et 2 % (m/m). • Les résultats obtenus montrent que l'augmentation de la concentration du borax dans l'adhésif diminue les performances mécaniques des composites. La meilleure façon d'éviter ce problème est de traiter le bois avec du borax, avant collage. • L'étude de la biodégradation a été réalisée sur les nouveaux composites, d'abord sans traitement, et après traitement à 0,5 % (m/m) avec du borax. Les résultats montrent que le bois traité au borax associé à la présence des tannins et de NaOH dans l'adhésif améliore la résistance totale des composites vis-à-vis de Coriolus versicolor et Coniophora puteana

Preparation and mechanical characterization of particleboard made from maritime pine and glued with bio-adhesives based on cornstarch and tannins

In this presented work, we describe the development and characterization of a new, environmentally friendly adhesive derived from cornstarch and tannins. The production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as urea formaldehyde (UF), phenol formaldehyde (PF) and melamine urea formaldehyde (MUF), which can generate under certain conditions, problems for health and environment. The aim of our work is to replace totally these synthetic resins. In order to evaluate the quality of cornstarch-tannin adhesives, particleboards were produced and physical and mechanical properties were investigated. These physical properties included rheological, thermogravimetric analysis and solid phase 13C NMR analysis of resins. Internal bond, surface soundness, modules of rupture and modulus of elasticity mechanical properties of particleboards bonded with cornstarch-tannin adhesives were also determined. Particleboards bonded with formaldehyde-free cornstarch-tannin adhesive showed comparable mechanical properties to the panels made with the commercial UF resins and satisfied the exigencies of panels for interior fittings used in dry medium (P2) according to European norms EN 312 (2004). Beyond 4 hours, rheological characterization show excellent structural stability of cornstarch-tannin adhesive

MALDI-TOF Analysis of Aleppo Pine (Pinus halepensis) Bark Tannin

Matrix-assisted laser desorption/ionisation time of flight (MALDI-TOF) mass spectrometry is a suitable method for examining polyflavonoid tannin oligomers because it has the capability to determine aspects of their oligomeric structure and characteristics that are too difficult to determine by other techniques. For non-purified industrially extracted Aleppo pine polyflavonoid tannin, it was possible to determine by MALDI-TOF that: (i) oligomers formed by catechin/epicatechin are present in tannin, as are mixed oligomer units with fisetinidin and robinetinidin units; the presence of flavonoid gallate and other structures was confirmed; (ii) oligomers up to 12 to 13 repeating monoflavonoid units, in which the repeating unit is at 264 Da, have been confirmed; and (iii) oligomers of the two types covalently linked to each other also occur. The presence of a small proportion of hydrolysable tannins by chemical analysis can also be explained by gallate residues attached to some of the flavonoid oligomers