Review Articles

A timber-concrete composite structure has the advantages of energy saving, environmental protection, and low carbon, and has wide application prospects. However, the effects of fire on timber-concrete composite structures are complicated. It is important to study the fire performance of connections and their influencing factors for the promotion and application of timber-concrete composite structures. This paper summarizes the research progress of connections for timber-concrete composite structures under fire. Firstly, research on the performance of connections in timber-concrete composite structures under fire is introduced, including screwed connections, notched, and grooved connections, and steel truss plate connections. Secondly, the calculation methods focused on connections of timber-concrete composite structures under fire are introduced. Finally, the main points of modeling timber-concrete composite structures under fire are also briefly introduced.

This review article is dedicated to special polysaccharide esters – the polysaccharide toluenesulfonic acid esters (tosylates) and polysaccharide carbonate esters. After describing the specifics of the synthesis, particular emphasis is placed on the use of polysaccharide tosylates and polysaccharide phenyl carbonates for subsequent modification by nucleophilic substitution (SN) reactions. For this purpose, the advantages and limitations of the respective derivatives are discussed with regard to their application in chemical modification with nucleophiles containing functional groups. A few functional polysaccharide derivatives and their properties are presented. Finally, reactive derivatives for click chemistry approaches are featured. These can be prepared starting from the reactive intermediate of either polysaccharide tosylate or polysaccharide phenyl carbonate.

Population and pollution make notable contributions to introducing novel sophisticated techniques. From vehicles to industries, the release of CO2 into the atmosphere and wastewater into the running water streams are key concerns. On the other hand, the population is responsible for the rapid manufacturing of all commercial goods. Microalgae are the only answer accessible for the aforementioned difficulties. Similar to plants, microalgae need CO2 and light to thrive and produce a variety of bioproducts such as carbohydrates, protein, lipids, vitamins, sterols, pigments, and silica. Physical (light, temperature, CO2, and UV), chemical (nutrient addition or depletion), enzymatic, and metabolic pathway reconfiguration, as well as indoor or outdoor growing, are highly regarded among the several optimization strategies to make desired products. Wastewater pollution is rectified by growing microalgae in nutrient-rich organic water for their growth, which is used to accelerate bioproducts. This review considers the use of bioproducts in food, animal and aquatic feed, fertilizer, biofuel, medicinal and nutraceutical sectors. This paper also provides different optimization strategies, which include physical and chemical means of extraction methods for enhancing bioactive products. Challenges and future recommendations for enhancing target bioproducts are discussed to overcome environmental issues.

There is a global trend to replace the production of conventional recyclable plastics with biobased ones, allowing a sustainable alternative adapted to the current concept of a circular bioeconomy. Forest-industrial and agricultural biomass wastes (lignocellulosic biomass waste, LCBW) produce severe problems in some developing countries because they are improperly disposed of or burned in the open air. Such wastes are attractive as a raw material to produce bioplastics due to their low cost. Furthermore, low-pollution processes can complete an economical and environmentally friendly approach. This review focuses on bio-polyethylene furanoate (PEF) production from LCBW as an alternative for polyethylene terephthalate (PET), one of the most widely used fossil-based plastic. The standpoint is based on the replacement of fossil-based monomers for the manufacture of PET, terephthalic acid (TPA), and ethylene glycol by two bio-based monomers, namely 2,5-furandicarboxylic acid (FDCA) and bio-ethylene glycol (Bio-MEG). This study describes the processes to obtain each bio-monomer, as well as the resulting polymers’ performance aspects, biodegradability, environmental and economic considerations, and recycling.

The global production of coconut, mainly for food and oil production, exceeds 62 million tonnes per annum. Large quantities of coconut husk remain unutilized after industrial processing, giving rise to environmental problems. This fails to exploit the potential presented by the extraction of coir, which could have numerous applications. Traditional products such as textiles, mats, and brushes made from coir are increasingly being joined by new, high-value, non-traditional uses. This review article summarizes new fields of application for coir as reinforcing fibers in binderless fiberboards, natural fiber composites, construction materials, solid biofuels, and an absorbent for heavy metals and toxic materials. The use of coir in these new fields will reduce waste and increase sustainability.

Vegetal fibers from different sources, including wood fibers and plant-derived fibers, together with polymer plastics per se (natural, synthetic, and their blends), as well as their combinations as composite materials may generate significant amounts of wastes. These will undergo degradation process under exposure to different environmental factors including microorganisms, climatic changes – e.g. droughts, oxygen, temperature, soil dynamics, UV radiation, etc. This survey offers a concise review of degradation under environmental conditions, mainly after in-soil exposure, of waste made of polymer materials and natural fibers. It also describes the most common methods for evaluation of bioconversion and degradation, as well as the structural properties after degradation (e.g. macroscopic investigation; weight loss; spectrometry – UV, FTIR, NMR; X-ray diffraction for crystalline changes; SEM microscopy; and thermal stability).

Wood is a non-homogeneous and orthotropic natural polymer material. It is important to test the wood shear modulus and elastic constants accurately and reliably using dynamic methods. Based on the introduction of the advantages of six common methods for dynamic testing of wood shear modulus, such as free plate torsional mode method, free bar torsional vibration method, and Timoshenko beam iterative method, issues associated with the applicability and accuracy of these methods are also pointed out. Recent methods, such as the free square plate torsional mode method and the square plate static torsional strain method, that were developed to dynamically test the shear modulus of wood and wood composite materials, are presented as effective ways to tackle these issues. These new approaches are expected to provide beneficial technical support for using small specimens, overcoming the size effect of specimens, simplifying the testing procedures, improving the test accuracy, and expanding the application range in the dynamic testing of wood shear modulus. These approaches have practical significance in promoting the industrialization and development of structural engineering, furniture and interior decoration, transportation, military, and musical instrument industries.

The increasing popularity of single-use wet wipes across a variety of applications has caused environmental and economic challenges. Due to their convenience and low cost, disposable nonwoven wipes have become a necessity in the lives of many. However, consumers rarely consider the end-of-life of these items. Despite efforts from stakeholders, including wipes manufacturers and wastewater experts, there is frequent confusion among consumers regarding appropriate disposal. Many consumers flush wipes that are not compatible with municipal sewer systems, causing considerable damage. Additionally, wipes have poor environmental outcomes, as they often contain non-renewable plastics or are unable to biodegrade under disposal conditions. Previously, the wet wipes industry was projected to grow an average of 6% between 2021 and 2025; however, the use of these disposable items is projected to be much higher due to the COVID-19 pandemic. This paper reviews the market, key challenges, and technical properties of single-use nonwoven wipes. An emphasis is placed on the unique properties and associated challenges of flushable wipes. With strong market demands, consumers are unlikely to abandon single-use wipes, and therefore innovative solutions are required to solve the main environmental and technical challenges associated with flushable and non-flushable wipes.

Wood utilisation is an important factor affecting production costs, but the combined utilisation rate of wood is generally only 50 to 70%. During the production process, the rejection scheme of wood defects is one of the most important factors affecting the wood yield. This paper provides an overview of the main wood defects affecting wood quality, introduces techniques for detecting and identifying wood defects using different technologies, highlights the more widely used image recognition-based wood surface defect identification methods, and presents three advanced wood defect detection and identification equipment. In view of the relatively fixed wood defect recognition requirements in wood processing production, it is proposed that wood defect recognition technology should be further developed toward deep learning to improve the accuracy and efficiency of wood defect recognition.

Tissue paper is deep-rooted in our daily life because of its different types of products that allow various applications. Tissue paper is a low grammage paper that is mainly characterized by softness, tensile strength, liquid absorption, and elasticity. These characteristics are essential when producing products such as toilet paper, kitchen rolls, hand towels, napkins, and facials. The tissue paper production involves two stages: formation of the tissue paper sheet itself and its converting into different finished products. Converting is characterized by several operations, namely: unwinding, winding, embossing, lamination, perforation, cutting, packaging, and palletizing. The most impacting operation is the embossing, which consists of marking a pattern on the paper sheet by applying pressure, with the intent to produce papers more aesthetically pleasing to the final consumer and/or a way to identify a particular brand. Also, it affects final properties, increasing the liquid absorption capacity and bulk but reducing softness and tensile strength. Converting is complex and has a huge impact on the finished products properties. In this review, the authors explored the different steps of converting and how they impact the different properties of finished tissue products.