Wood Adhesives Based on Natural Resources: A Critical Review Part II. Carbohydrate-Based Adhesives

2020 ◽  
Vol 8 (3) ◽  
pp. 333-378
Author(s):  
Manfred Dunky
Keyword(s):  
Citric Acid ◽  
Natural Resources ◽  
Water Resistance ◽  
Fibre Surface ◽  
Huge Number ◽  
Decomposition Products ◽  
Wood Adhesives ◽  
Synthetic Chemicals ◽  
Scientific Papers ◽  
Natural And Synthetic

This Part II of the series of critical reviews on Wood Adhesives Based on Natural Resources concentrates on the various carbohydrates and their decomposition products, which might be used as wood adhesives. This includes the use of native carbohydrates as such as adhesives, and also with chemical modification of carbohydrates by natural and synthetic components. Crosslinking in order to improve moisture and water resistance is achievable by natural and synthetic chemicals. Most promising options are realized by decomposition of various carbohydrates to small, well-defined monomers, which then can undergo various reactions, yielding again polymers in order to create a bondline. Suitable monomers are various furan moieties, such as 5-hydroxymethylfurfural. Activation of cellulose and hemicellulose at the wood or fibre surface by chemicals, such as citric acid, enables bonding effects without addition of an external adhesive. So far, however, carbohydrates are used only in very small amounts as industrially applied wood adhesives, despite tremendous R&D effort made and a huge number of scientific papers and reports published.

scholarly journals Sustainability and Resilience of Emerging Cities in Times of COVID-19

2021 ◽  
Vol 13 (16) ◽  
pp. 9480
Author(s):  
Angela Ivette Grijalba Castro ◽  
Leonardo Juan Ramírez López
Keyword(s):  
Urban Planning ◽  
Natural Resources ◽  
Main Argument ◽  
State Of Emergency ◽  
Ecological Footprints ◽  
Scientific Papers ◽  
Considerable Impact ◽  
New Challenges ◽  
Meta Analyses

The organization of a territory relies on a group of transformations produced by economic, environmental, and social emergencies, generating disruptions along with history. Furthermore, every new scenario generates a considerable impact, which makes it more difficult to recover from increasing urban ecological footprints. COVID-19-emergence-aware cities face new challenges that will test their resilience. This new outline constitutes a study regarding urban planning from an environmental and resilience perspective within this new pandemic state of emergency. It contains four main topics: emergent cities, natural resources, sustainability, and resilience. The document shows a case study carried out in a Colombian town named Cajicá, where a bibliometric inquiry conducted with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) adjustments was managed, tested on forty-one scientific papers; all the above were verified by VOSviewer software tools. The study reveals the creation and visualization of several keyword networks and relations retrieved from all the selected articles, along with the use of eight additional documents for all relation analyses. Sustainability and resilience are the main findings, supported as a process of functionality within urban planning. Sustainability findings’ results are prioritized, along with resilience analysis processes, which are both frameworks used during the COVID-19 pandemic; they constitute the main argument within this set of changes, building on alterations of lifestyle and behavioral situations within the main cities.

scholarly journals Peanut meal-based wood adhesives enhanced by urea and epichlorohydrin

2019 ◽  
Vol 6 (11) ◽  
pp. 191154 ◽  
Author(s):  
Chen Chen ◽  
Fusheng Chen ◽  
Boye Liu ◽  
Yan Du ◽  
Chen Liu ◽  
...  
Keyword(s):  
High Performance ◽  
Water Resistance ◽  
Rapid Development ◽  
Peanut Meal ◽  
Decomposition Temperature ◽  
Solid Content ◽  
Added Value ◽  
Wood Adhesives ◽  
Plywood Industry ◽  
Reactive Groups

Peanut meal (PM) has recently emerged as a potential protein source for wood adhesives, owing to superior features such as high availability, renewability and eco-friendliness. However, the poor properties of unmodified PM-based wood adhesives, compared with their petroleum-derived counterparts, limit their use in high-performance applications. In order to promote the application of PM-based wood adhesives in plywood industry, urea (U) and epichlorohydrin (ECH) were used to enhance the properties of the adhesives and the modification mechanism was investigated. PM-based wood adhesives made with U and ECH were shown to possess sufficient water resistance and exhibited higher apparent viscosity and solid content than without. Fourier-transform infrared spectroscopy results suggested that U denatured PM protein and expose more reactive groups, allowing ECH to react better with U-treated PM protein to form a dense, cross-linked network which was the main reason for the improvement of the properties. The crystallinity increased from 2.7% to 11% compared with the control, indicating that the molecular structure of the resultant adhesive modified by U and ECH became more regular and compact owing to the cross-linked network structure. Thermogravimetry tests showed that decomposition temperature of the protein skeleton structure increased from 307°C to 314°C after U and ECH modification. Scanning electron microscopy images revealed that using U and ECH for adhesives resulted in a smooth protein surface which prevented moisture penetration and improved water resistance. PM-based adhesives thus represent potential candidates to replace petroleum-derived adhesives in the plywood industry, which will effectively promote the rapid development of eco-friendly adhesives and increase the added value of PM.

Citric Acid - Its Natural and Synthetic Derivatives

2010 ◽  
Vol 28 (6) ◽  
pp. 204-211 ◽  
Author(s):  
Maria J. Milewska
Keyword(s):  
Citric Acid ◽  
Synthetic Derivatives ◽  
Natural And Synthetic

scholarly journals Metabolic Modelling Approaches for Describing and Engineering Microbial Communities

2020 ◽  
Author(s):  
Beatriz García-Jiménez ◽  
Jesús Torres ◽  
Juan Nogales
Keyword(s):  
Microbial Communities ◽  
Microbial Consortia ◽  
Huge Number ◽  
Metabolic Modelling ◽  
Rational Engineering ◽  
Wet Lab ◽  
Synthetic Microbial Communities ◽  
Advance Knowledge ◽  
Natural And Synthetic

Microbes do not live in isolation but in microbial communities. The relevance of microbial communities is increasing due to the awareness about their biotechnological influences in a huge number of environmental, health and industrial processes. Hence, being able to control and engineer the output of both natural and synthetic communities would be of great interest. However, most of the available methods and biotechnological applications (both in vivo and in silico) have been developed in the context of isolated microbes. In vivo microbial consortia development, i.e. to reproduce the community life conditions in the wet-lab, is extremely difficult and expensive requiring of computational approaches to advance knowledge about microbial communities, mainly with descriptive modelling, and further with engineering modelling. In this review we provide a detailed compilation of available examples of engineered microbial communities as a launch pad for an exhaustive and historical revision of those computational methods devoted so far toward the better understanding, and rational engineering of natural and synthetic microbial communities.

Wood Adhesives Based on Natural Resources: A Critical Review: Part IV. Special Topics

2021 ◽  
Vol 9 (2) ◽  
pp. 189-268
Author(s):  
Manfred Dunky
Keyword(s):  
Natural Resources ◽  
Phenol Formaldehyde ◽  
Direct Synthesis ◽  
Cellulose Nanofibrils ◽  
Raw Material ◽  
Poly Lactic Acid ◽  
Natural Polymers ◽  
Wood Adhesives ◽  
Cashew Nut ◽  
Wood Bonding

Various naturally-based chemicals can be used directly as wood adhesives or are precursors for the synthesis of adhesive resins. Liquefaction and pyrolysis of wood yield various smaller chemicals derived from the different wood components, which then are used in the preparation of adhesives by replacing mainly phenol as raw material. The possible replacement of formaldehyde in aminoplastic and phenolic resins would solve the question of the subsequent formaldehyde emission.<br/> The multiple unsaturations of the triglycerides in vegetable oils enable polymerization for the direct synthesis of thermosets, as well as bases for polyfunctionalization and crosslinking.<br/> Natural polymers, such as poly(lactic acid)s (PLAs), natural rubber, or poly(hyhydroxyalkanoate)s (PHAs) are thermoplastics and can be used for various special applications in wood bonding, in case they can also be crosslinked. For other thermoplastic wood adhesives, such as PUR or PA, chemicals based on natural resources can at least replace a part or even all synthetic raw materials (monomers); these monomers derive from targeted decomposition of the wood material in biorefineries.<br/> Cellulose nanofibrils (CNFs) can be used as as sole adhesives or as components of adhesives. Hydrogen bonding has a key function in binder applications related to adhesion between cellulose nanoparticles and other materials. CNFs are able to establish strong bonding between wood particles/fibres through flexible and strong films by a simple drying process.<br/> Cashew nut shell liquid (CNSL) is a by-product of the cashew nut processing with cardanol (CD) as main component. CD-formaldehyde resins show improved flexibility compared to phenol-formaldehyde (PF) resins; CD can replace up to 40% of the phenol.

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