Volume 13 Issue 1

The present study was conducted to determine the influence of the chemically modified kenaf bast fiber (KBF) on the mechanical, morphological, and thermal properties of fiber-reinforced polypropylene composites. The KBF was modified via the in situ sol-gel silica process through soaking the KBF in tetraethyl orthosilicate (TEOS) at a pH of 11, room temperature (25 °C ± 1 °C), and a KBF to TEOS ratio of 1:10 for 24 h. Silica successfully formed on the surface of the KBF. Subsequently, the sol-gel silica-modified KBF was utilized to produce sol-gel silica-modified KBF-reinforced polypropylene (PP-KBF-S) composites. Several analytical methods were utilized to determine the mechanical, morphological, and thermal properties of the PP-KBF-S composites, which were then compared with those of the untreated KBF-reinforced polypropylene composite. The findings revealed that sol-gel silica modification of the KBF reduced the void content and enhanced the mechanical properties and thermal stability of the PP-KBF-S.

As the world’s leading civil construction materials, concrete and mortar are the focus of ongoing studies aimed at improving their properties.  These materials are highly versatile; hence, some of their aspects, such as their interaction with toxic materials, should be examined in greater depth. An investigation was therefore undertaken to ascertain how these products react to phorbol ester (PE), a toxin found in Jatropha seed cake (JSC). The mechanical behavior of mortar and concrete containing JSC waste from the manufacture of biofuel was examined based on the analysis of axial compressive strength. The interaction between mortar and PE molecules was examined by means of high performance liquid chromatography. A study of the mechanical behavior of the materials indicated that the inclusion of JSC greatly reduced their mechanical properties, and that this inclusion had a stronger impact on mortar than on concrete, while liquid chromatography showed that the toxic material inserted into the mortar remained inert, indicating the promising potential of this material to store toxic products.

The mean arithmetic deviation of the roughness profile was investigated during cylindrical milling of the board edges. The machined materials were a medium-density fiberboard, medium-density fiberboard with single-sided lamination, and edge-glued spruce panel. Contactless and contact profilometers were used to measure the roughness. Both methods were evaluated and compared. Tungsten carbide blades with three different compositions and treatments were used. The effect of the cutting speed (20 m/s, 30 m/s, 40 m/s, and 60 m/s) and feed rate (4 m/min, 8 m/min, and 11 m/min) on the surface roughness was also monitored. The results of this study compared two different methods for determining the surface roughness. The measurements were more accurate with a contactless profilometer, but the price is higher than that of the contact method. The operation was also more complicated, and the measurement itself took longer with a contactless profilometer. The evaluation of individual surface quality variables was faster with a contact device. The best results in terms of the surface quality were achieved by lowering the feed rate and increasing the cutting speed.

Mechanical properties are among the properties to be considered in designing and fabricating any composite to be used as a firewall blanket in the designated fire zone of an aircraft engine. The main focus of this work was to study the tensile, compression, and flexural strengths of the combination of natural/synthetic fibres with metal laminates as reinforcement in a polymer matrix. The materials included flax fibres, kenaf fibres, carbon fibres, aluminium alloy 2024, and epoxy. The two-hybrid fibre metal laminate composites were made from different layers of natural/synthetic fibres with aluminium alloy of the same thickness. The composites were made from carbon and flax fibre-reinforced aluminium alloy (CAFRALL) and carbon and kenaf fibre-reinforced aluminium alloy (CAKRALL). Based on the results obtained from the mechanical tests, the CAFRALL produced better mechanical properties, where it had the highest modulus of elasticity of 4.4 GPa. Furthermore, the CAFRALL was 14.8% and 20.4% greater than the CAKRALL in terms of the tensile and compressive strengths, respectively, and it had a 33.7% lower flexural strength. The results obtained in the study shows that both composites met the minimum characteristics required for use in the fire-designated zone of an aircraft engine due to their suitable mechanical properties.

The water repellency, elastic modulus, and hardness of hydrophobic-treated and untreated wood cell walls were investigated. Chinese fir (CF; Cunninghamia lanceolata (Lamb.) Hook) wood was modified using polydimethylsiloxane (PDMS) and dimethyldichlorosilane (DMDCS) dissolved in n-hexane at 2%, 5%, and 8% (w/w) for 5 min, 30 min, and 2 h, respectively. A hydrophobic property was observed in the modified wood. The water contact angle value of the untreated wood surface was 85°, but after treatment this value increased to 147° and 143° for the PDMS- and DMDCS-treated wood, respectively. Increases in the elastic modulus and hardness of the wood cell wall were observed after PDMS treatment. These treatments also improved the water repellency of the wood surface, as verified by the reduction of the hydroxyl group O-H stretching vibrations at 3328   cm^-1. Compared to DMDCS, the PDMS treatment improved the hydrophobicity of wood surfaces and increased the nanomechanical properties of the wood cell wall. When an 8% concentration of PDMS and a 2 h treatment time were used, the treated wood showed the best mechanical properties.

The production of fiberboard, particleboard, and related hot-pressed biomass products can convert small, relatively low-valued pieces of wood into valuable products. There is strong interest in being able to manufacture such products without the addition of formaldehyde, which is a health hazard during both production and use.  This article reviews literature describing various challenges that need to be faced in order to achieve satisfactory bonding properties in hot-pressed bio-based board products without the addition of formaldehyde.  Bonding mechanisms are examined in the form of a hypothesis, in which the strength development is represented by a chain with four links.  Failure of a board is expected to occur at the weakest of these mechanistic links, which include mechanical contact, molecular-scale wetting and contact, various chemical-based linkages, and structural integrity.  The most promising technologies for environmentally friendly production of hot-pressed board with use of lignocellulosic materials tend to be those that favor success in the development of at least three of the mechanistic links in the hypothetical chain.

Wood is an abundant and renewable natural resource. Its use is promoted as a way to reduce the carbon footprint in building construction. Wood structures are degraded by their environment due to weathering. This review is a meta-analysis of the main factors of degradation that belong to this phenomenon. The impact of irradiation, the role of water, oxygen, temperature, and colonization by fungi are explained. To protect against these factors, the use of coatings is the most common solution. Since currently the trend is to maintain the grain and the natural color of the wood, the use of transparent coatings is favored. This review presents the main technologies used in clear wood coatings. The durability of this protection against weathering is approached. The whole of knowledge gathered has made it possible to begin a discussion on the multifactorial aspect of wood weathering. Schemes were created to synthesize the synergistic and antagonistic effects between the degradation factors.

The machining mechanisms in milling for medium-density fiberboard (MDF) and wood-plastic composites (WPC) are reviewed in this article. The study focuses on milling tool wear, chip formation mechanisms, processing stability, and machined surface roughness. The influence law of cutting parameters (cutting speed, feed rate, and cutting thickness), tool materials and geometry (rake angle, relief angle, and size parameters), temperature, and other factors on tool wear and machined surface roughness were considered. Concrete measures to improve tool life and machined surface quality are summarized as well as an online monitoring system of tool wear and machined surface roughness. Future research of tool wear and surface quality in milling wood-based materials is proposed to provide important references for wood-based materials researchers.

With the improvement of living standards, the human demand for antibacterial materials has increased. Cellulose, as the most abundant polymer in the world, is natural, biodegradable, and renewable, which makes it a promising raw material for the production of antibacterial materials. Silver nanoparticles (AgNPs)-cellulose antibacterial composites exhibit good biocompatibility and antimicrobial properties. These materials are easily degraded chemically and are environmentally friendly. Therefore, the AgNPs-cellulose antibacterial composites exhibit broad utilization prospects in environmental protection, medicine, chemical catalysis, and other fields. Several methods are used to manufacture such materials. This paper reviews three common techniques: the physical method, the in situ chemical reduction method, and the covalent bonding method. The differences and relationships are identified, and the advantages and disadvantages are compared among these three methods. Lastly, the present situation and the development potential of the AgNPs-cellulose antibacterial composites are discussed in this review.

The relevant literature is reviewed concerning eucalyptus wood collapse, with a focus on lumber drying technology. Potential future research is summarized regarding where potential future work may focus. Eucalyptus is often limited as a solid wood products material due to microstructural collapse and interior cracking that may occur during drying. To prevent the drying collapse, studies have focused on the mechanism of collapse, the morphological characteristics of collapse, the control of collapse, amongst other criteria. Because the surface tension of water results in wood cell collapse, the shape of collapsed cells should be recovered after the liquid tension disappears. Therefore, pretreating green timber (such as pre-heating, pre-steaming, microwave treatment, pre-freezing, or boiling) prior to drying results in the modification of wood cell tissue and inhibits the conditions for collapse. Thus, there is improved wood permeability, drying rate, shortened drying time, as well as reduced collapse during the drying process. In addition, applying process control in regards to a suitable drying schedule (especially the drying temperature), relative humidity, drying time, intermittent drying process, combined drying technology, etc., tends to reduce the amount of collapse and improve drying quality. Reconditioning, such as steaming during the drying process, can aid collapse recovery. Generally, reconditioning or other treatment can help recover 50% of the collapse.