Volume 16 Issue 3

The production of bioplastics is a growing trend. The utilization of renewable sources, in some cases currently wasted, to replace petroleum derivatives, is providing opportunities to achieve more environmentally friendly product life cycles. The possibility of producing biodegradable products under normal environmental conditions is another goal of recent studies. This editorial summarizes current aspects in the production of bioplastics. We highlight new studies that make it possible to obtain biodegradable composites using a natural, renewable, high availability, and low-cost material, such as cellulose.

Acquisition and isolation of value-added substances from natural sources using new types of green solvents are becoming a breakthrough area of 21st century research. In combination with various extraction techniques, there is expected to be a diversification of the use of these solvents for extraction, separation, and the formation of new drug carriers, allowing increased solubility of substances having potential pharmacological properties. Extraction, separation, or increase in the solubility of suitable drug candidates against COVID-19, or other viral diseases, opens new ways to effectively prevent and protect human health in this pandemic period.

Due to its renewable nature, its inherent strength, and many other favorable attributes, nanocellulose (NC) has drawn increasing attention for many potential applications. A diverse and complex assortment of NC products have been reported, and these are most commonly classified based on some contrasting procedures of preparation. The research community is facing a continuing challenge to adequately measure and quantify morphological features of various NC products. In principle, it ought to be possible to quantify and name NC based on such attributes as “degree of branching,” “breadth of particle size,” and “aspect ratio distribution,” etc. However, the ability to measure and compute such quantities still lies beyond what can be achieved in practical amounts of time in typical laboratories. Meanwhile, there has been tension between researchers proposing additional descriptive names, while at the same time there have been efforts at achieving uniformity and simplicity in nomenclature. It is proposed in this essay that this state of affairs is largely a reflection of complexity itself, such that NC products that have the same nominal description can be very different from each other when examined closely. The diversity itself may turn out to be a good thing, as researchers work to come up with varieties of NC that can survive an expected relentless competition from existing plastic-based or cellulose-based materials.

Wood is one of the most important building materials. Thermally modified wood is entering the market and replacing wood preservatives and tropical wood species in some applications. Thermally modified wood is exposed to weathering similarly as other wood-based building materials. It has been reported that if thermally modified wood is exposed to weathering, its moisture performance might decrease fairly fast. Moisture performance reflects the material’s ability to remain dry and dry out fast when wet. The aim of this study was to determine whether this phenomenon is associated with crack formation or roughness. Norway spruce, thermally modified spruce, wax-treated thermally modified spruce, and European larch heartwood samples were exposed to artificial accelerated weathering and natural weathering for 9, 18, and 27 months. Samples were subsequently isolated, and their roughness was determined with a confocal laser scanning microscope on axial and longitudinal surfaces at 10× and 50× magnification. After weathering, roughness increased on both axial and longitudinal surfaces. This was evident from the profile 2D measurements (Ra) and surface 3D measurements (Sa). The effect of natural weathering on roughness was higher than artificial accelerated weathering, presumably due to synergistic effects of abiotic and biotic factors. This may be associated with Wenzel’s theory on the influence of roughness on the contact angles of water on the surface; namely, increased roughness will decrease the contact angle on hydrophilic surfaces.

Effects of the heat treatment parameters were evaluated relative to some physical and mechanical properties of poplar wood (Populus alba L.) with use of two of the prominent multi criteria decision-making (MCDM) techniques: Entropy and The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). To meet this objective, the test samples were heat-treated at 120, 150, 180, and 210 °C for 2 and 4 h in a laboratory-scale oven. With increasing temperature and duration, the shrinkage and swelling ratios of heat-treated samples were improved. However, the bending strength, modulus of elasticity, and compression strength generally decreased with increasing process temperature and duration. According to (MCDM) analyses, thermal modification definitely improved the physical properties of wood up to a point. Bending strength was found to be the most important determinant of heat treatment success. The other determinants were identified as swelling, compression strength, shrinkage, and modulus of elasticity, respectively. Also, the best results were obtained at 120 °C for 2 h. In general, heat treatment above 150 °C or 4 h is not recommended.

Tree decline is a physiological phenomenon resulting from climatic disturbances that involves damage to forest ecosystems. This study examined the effects of tree decline on nutrient concentrations in the leaves, bark, and wood of Persian oak (Quercus brantii) trees. Trees were categorized by decline severity (healthy, slight, moderate, and severe decline). Leaves were collected from the middle and outer parts of the crowns. Bark and wood samples were taken at breast height (1.3 m). The contents of Mg, Ca, P, Fe, K, and Na were analyzed by atomic absorption spectrophotometry and flame photometry. As decline severity increased, the concentrations of Mg, Ca, P, Fe, K, and Na in the foliage increased. However, the P and K in the bark and the P in the wood were lower in trees in the higher decline classes. Moreover, nutrient contents in the tissues examined varied across the different decline severities. The variations may have been due to defense mechanisms of the trees enhancing tolerance against induced stress. The results suggested that nutrient stoichiometry can reflect uptake in forest ecosystems and plant-environmental stress relationships.

Microwave pyrolysis of finely ground jatropha seed biochar was used as bio-filler to develop biocomposites. Effects influencing the mechanical properties of the biocomposites were investigated based on varied material ratio. Ratios by percentage of weight were determined by D-optimal (custom) mixture design using the Stat Ease “Design Expert”. The mechanical properties, such as tensile strength, modulus of elasticity, and microhardness, were the dependent variables (response). Bio-filler content was optimised to attain the overall best mechanical properties for the biocomposites. The optimized biocomposite that showcased good tensile strength, modulus of elasticity, and microhardness biocomposite ratio’s predicted mechanical properties mean values were tensile strength (9.53 MPa), modulus of elasticity (0.730 GPa), and microhardness (20.4 HV) for polylactic acid and biofiller mixture; and tensile strength (7.92 MPa), modulus of elasticity (0.668 GPa), and microhardness (18.7 HV) for polylactic acid, biofiller, and poly(ethylene-alt-maleic anhydride) mixture. Models generated by the mixture design showcased some degree of noise and error present; however, the outcome through the optimization step was generally reliable for predicting the mechanical properties. Additional data gathered through experimental testing and replicates could improve the reliability of the model.

Thyme oil, which is an anti-fungicide, was used to increase the physical and mechanical properties of wood as well as improve its strength, especially in outdoor conditions. For this purpose, Stone pine (Pinus pinea L.) wood samples classified according to the annual number of rings were exposed to either the impregnation process or the combined process, which was comprised of impregnation followed by heat treatment. As a result of the study, it was determined that the wood had different physical and mechanical properties based upon the number of annual rings. In addition, it was specified that the thyme oil used in the impregnation process improved the physical properties of the wood and also reduced the water absorption during the combined process. As a general conclusion, the impregnation process and the combined process increased the mechanical properties of the wood in parallel with an increase in the number of annual rings. The process of impregnation of wood materials with thyme oil is promising due to its anti-fungal and antibacterial properties, its ability to be used in small amounts in on-site impregnation, and it being an environmentally friendly product for the wood protection industry.

The antioxidant activity, total polyphenol content (TPC), and total flavonoids content (TFC) of sea buckthorn juice was analyzed with electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-VIS) in ethanol, methanol, and acetone extracts. The choice of a suitable solvent system is necessary so as not to skew the results. Undiluted juice of sea buckthorn berries is not suitable for the mentioned analyzes. Sea buckthorn juices were evaporated under vacuum until completely dry and then dissolved in 100% methanol, 96% ethanol, 70% ethanol, and 50% acetone. The 70% ethanol extract of sea buckthorn juice had an average of 1.3- and 1.6-times greater TPC and TFC values than other extracts, respectively. The 70% ethanol extract of juice contained 29 mg gallic acid equivalents (GAE)/g dw and 4 mg catechin equivalents (CE)/g dw. The results of the antioxidant activity of the extracts determined by EPR spectroscopy had an error rate ~ 2.5 times lower than the UV-VIS analysis. The highest antioxidant activity (123 mmol of Trolox equivalents/kg extract) was determined with EPR and ABTS radical in the 70% ethanol extract. This method correlated well with the TFC levels.

Bamboo dissolving pulp (BP)/chitosan (CS) blend solutions were obtained by adding different weight ratios of BP and CS particles to N-methyl-morpholine-N-oxide (NMMO) solvent. The processing and membrane-forming performances of the blend solutions were studied using a rotating rheometer. The BP/CS blend solutions’ optimal processing temperature was 50 to 70 °C. When the CS weight ratio was 9.09 wt%, the viscosity of the solution decreased, which was conducive to the processing of the membrane. The BP/CS blend ultrafiltration membranes were prepared by phase transformation of the blend solutions. The results showed that the rejection rate of the BP/CS blend ultrafiltration membrane with physically added CS particles was greatly improved compared with that of the regenerated BP ultrafiltration membrane.