Volume 15 Issue 2

Natural materials such as wood, bone, and skin continue to command the respect and admiration of materials scientists. It is difficult to achieve comparable properties by the use conventional industrial manufacturing processes. In this essay we are proposing a radical approach to the preparation of future intelligent packaging materials. Rather than attempting to assemble the chemical components at a nano-scale to make an intelligent package, our proposal is to let life itself take care of much of the assembly. We propose that the natural growth of bacterial cellulose can be used as a way to prepare a well-integrated structure at the nano-scale. Additives such as natural dyes can be introduced already during biosynthesis and thus become well integrated with the packaging material from the start. For example, one can develop a smart label for pH monitoring based on bacterial cellulose doped with natural dyes extracted from natural byproducts by in situ biosynthesis of cellulose. The resulting film has potential to be used as a visual indicator of the pH variations during storage of packaged food.

Assembly of biofibers into paper-based products fits well into green chemistry principles. Biobased additives such as cationic starch and carboxymethyl cellulose are widely used in the paper industry. Edible additives, which often can be regarded as “safer” than regular biobased additives, may also play a role in tailorable design of paper-based products.

The increase of filler content in paper is an effective way to reduce production costs and to promote the market competitiveness of paper mills. A shift from natural fillers to synthetic fillers has enabled improvements in the critical properties of paper. Meanwhile, innovations from single particles of filler to filler composites has made it possible to increase the filler content of paper. Among various filler innovations, the design of fiber/filler composites has aroused general attention from industry and academic researchers. However, concerns related to the cost and recyclability of composite fillers remain to be addressed.

A novel green approach was developed for producing silver nanoparticles (AgNPs) using lignocellulose nanofibrils (LCNF). This method does not require any additional reducing agent, and the LCNF itself serves both as a reducing agent and a supporting material. A simple autoclave procedure was employed for the synthesis. The synthetic conditions such as concentrations of reactants and reaction time were optimized. Also, the effect of lignin content in LCNF on the formation of AgNPs was evaluated. Three types of cellulose nanofibrils, i.e., HCNF (0% lignin), LCNF-5 (5% lignin), and LCNF-18 (18% lignin), were employed for the preparation of AgNPs. Three types of AgNPs were obtained and thoroughly characterized using UV-vis, Fourier-transform Infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results suggest that LCNF can be employed as a green source for the reduction and effective stabilization of AgNPs, but an increased content of lignin can have an adverse effect on the yield of AgNPs. However, the presence of lignin greatly influenced the particle size. Therefore, LCNF with small amounts of lignin (5%) is best for producing AgNPs.

Ferromagnetic activated carbon (FAC) was prepared through impregnation of cassava peel with FeCl3 (3.75%) solution and pyrolyzed at 800 °C. Samples were characterized using iodine number, methylene blue number, X-ray fluorescence, Fourier transformation infrared, X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled to energy dispersive X-ray spectroscopy, elemental analysis and N2 adsorption for surface area determination. The proximate analysis of cassava peel showed that the moisture content, fixed carbon, ash content, and the volatile matter were 3.52%, 82.97%, 4.97%, and 8.54%, respectively. The prepared FAC had a BET surface area of 405.9 m2/g, pore size of 2.03 nm and total pore volume of 0.11 cm3/g. The SEM analysis showed the presence of both micro and mesopores on the FAC sample. The XRD pattern of FAC showed the presence of characteristic peaks of magnetite–maghemite, confirming that the prepared material is ferromagnetic. According to the experimental results, the cassava peels are considered as appropriate raw material for FAC preparation.

Essential oil emulsion, which is generally functionalized to have increased antifungal activity, has high solubility in water. The objective of this research was to develop an essential oil emulsion for absorption by water hyacinth plants in order to produce an essential oil absorbent material as a carrier of essential oil vapor that can be released to control mold in an enclosed packaging system. The fresh water hyacinth adsorbed the Michelia alba oil emulsion (100 µL/mL to 500 µL/mL) through its root system, transporting it to the stems and leaves after submerging the plant into the M. alba oil emulsion for 48 h. Dried sections (root, stem, and leaf) of the water hyacinth plant with absorbed M. alba essential oil emulsion released the M. alba vapor, inhibited Aspergillus flavus growth on malt extract agar (MEA), and also Thai dessert (Ja Mongkut) with the highest antifungal activity achieved with the concentration 500 µL/mL. The maximum essential oil absorption (345 µL/g) in the fresh plant was achieved after 48 h. The dried water hyacinth (≥ 0.4 g/L air) completely inhibited the growth of A. flavus for at least 7 days. In addition, the absorbent material prevented the growth of A. flavus on the Thai dessert (Ja Mongkut) with approximately 100% effectiveness (versus the control) for 10 days, thereby extending the shelf-life 2.5-fold in when compared with the control without essential oil.

A high-density particleboard composed of peanut shells (Arachis hypogaea L.), an agro-industrial residue, and bamboo wastes of the species Dendrocalamus giganteus (branches and apical part), bonded with a two-component polyurethane resin based on castor oil (Ricinus communis L.) in the proportion of 12% of the particleboard mass, was produced. Four types of specimens were prepared according to the percentage of peanut shells: 0%, 10%, 20%, and 30%. Mechanical characteristics were evaluated through the flexural strength tests for modulus of rupture, modulus of elasticity, perpendicular traction, and screw pull resistance. The particleboard reached an average density of 917.2 kg/m3, meaning that it could be classified as high-density particleboard. The results of the mechanical tests indicated that the specimens containing a mixture in the proportion of 90% bamboo and 10% peanut hull presented the best mechanical strength. The experiment produced particleboards with a satisfactory mechanical physical performance that met the standards ABNT NBR 14.810-2 and ANSI A208-1, supporting the use of the peanut shell residue in the manufacture of particleboards to be used in internal environments and allowing the applicability of this residue through additional value.

A new type of structural element, the timber-concrete composite beam, exhibited excellent structural performance. The notched connector is widely used in timber-concrete composite systems as a result of its considerable shear capacity and stiffness. Six groups of push-out tests were performed to investigate the shear performance of the notched connectors for the timber-concrete composite beams, with consideration to the varying concrete types, the shear length of the timber, and whether the notch was reinforced. From the test results, the notched connectors that corresponded to the shear fracture of concrete or timber had a low shear capacity and poor ductility. Notched connectors that simultaneously failed at the concrete slab (via shear force), as well as at the lag screw reinforcement point during bending presented the greatest shear capacity. This was followed by the notched connectors that exhibited diagonal-compression failure at the concrete slab. Screw fasteners in the notch were shown to improve the strength, ductility, and post-peak behavior of the notched connectors. In addition, the concrete type, the shear length of the timber, and whether the notch was reinforced were found to have no major influence on the slip modulus of the notched connectors.

Wood is both renewable and natural, which are qualities that make it both environmentally sustainable and useful in terms of development. However, wood also has certain inherent defects, such as its tendencies to shrink when dried and rot when wet. These defects restrict the use and popularity of lumber as a building material. In this paper, the effects of beeswax impregnation on the dimensional stability of wood were studied. Pieces of African padauk (Pterocarpus soyauxii) (20 mm × 20 mm × 20 mm) were used as the test material. The wood was treated at a temperature of 120 °C for periods of 3 h or 6 h. Measurements of weight gain rate, size expansion coefficient, and contact angle of the control samples were compared with samples treated with beeswax for 3 h and 6 h to explain macroscopic changes in wood. The effects of beeswax impregnation were compared using scanning electron microscopy, thermal weight loss characteristic analysis, and functional group analysis. The results indicated that, to some extent, beeswax impregnation improved the dimensional stability of wood and remarkably enhanced its surface hydrophobicity.

Melamine urea formaldehyde (MUF) resin impregnation followed by heat compression is a prominent method in improving mechanical properties and dimensional stability of wood. In addition, melamine is reactive to formaldehyde, and therefore able to reduce the free formaldehyde of the treated wood. This study aimed to produce compressed sesenduk (Endospermum diadenum) wood with low formaldehyde emission using low viscosity MUF resin. The effects of treatment efficiency on the physical and mechanical properties of the wood products were evaluated. The experimental design included impregnation of sesenduk strips with 20% and 30% MUF at five different formulations. Then, it was pre-cured at a temperature of 70 °C for 90 min, followed by hot compression at 140 °C with the compression ratio of 80%. The optimum treatment combination was determined through treatability, mechanical strength, dimensional stability, and formaldehyde emission. It was also compared to other treatments, including impregnation without further compression using formulated MUF and commercial MUF. The results revealed that F4 MUF, which consisted of 30% melamine, 50% formaldehyde, and 20% urea, was the optimal MUF formulation that resulted in low formaldehyde emission and acceptable physical and mechanical properties.