European Journal of Wood and Wood Products最新文献

In this paper, a dynamic vapor sorption analyzer in conjunction with the Dino-Lite Edge Digital Microscope was utilized to study the moisture sorption and thickness variation characteristics of the surface and core layers of impregnated paper coated fiberboards (IPCF) and its substrate high density fiberboards (HDF) at different temperatures. Results showed that the equilibrium moisture content (EMC) of both the surface and core layers of IPCF was reduced by the impregnated paper coating, and their dimensional stability as well as dimensional recovery performance after swelling was enhanced. A different phenomenon from previous studies was observed, the EMC of both the surface and core layers of IPCF and HDF increased with the increase of temperature. It can be affirmed that this phenomenon is not related to capillary condensation water. In addition, both the surface and core layers of IPCF and HDF exhibited moisture sorption hysteresis and swelling hysteresis during the moisture sorption cycle, both of which showed opposite responses to temperature. The sorption hysteresis and swelling hysteresis were affected by the degree of melamine-urea–formaldehyde (MUF) resin crosslinking and porosity, respectively. The higher the crosslinking degrees of the MUF resin in fiberboard, the greater the absolute hysteresis; swelling hysteresis is negatively correlated with porosity.

The growing demand for polymeric materials has made them significant in both industry and the environment, and the task of making them sustainable is becoming increasingly challenging. Cellulose presents an opportunity to minimize the effect of nondegradable materials. Cellulose nanofibers (CNFs) are a class of cellulose fibers with superior performance due to their high strength and stiffness combined with low weight and biodegradability. This work aimed to produce composites using low-density polyethylene (LDPE) as a matrix and CNFs from Pinus sp. (Pinus) and Eucalyptus sp. (Eucalyptus) as reinforcements. The CNFs were obtained by mechanical defibrillation of the cellulose, and subsequently, the water was removed by centrifugation to produce a master with CNFs and LDPE using a thermokinetic homogenizer. The master was milled and blended with LDPE to obtain booster concentrations of 1, 2 and 3% by weight (wt%). To characterize the composites, tensile and flexural tests and thermal and rheological analyses were performed. An increase of between 3 and 4% in the crystallinity of the composite was observed with the addition of Pinus CNF, and a decrease of 2 to 3% in the crystallinity index was observed with the addition of Eucalyptus CNF. The thermal stability increased for all the compositions. For the mechanical properties, increasing the CNF content increased the stiffness and tensile strength. In general, this process is an effective alternative for producing composites of LDPE with cellulose nanofibers.

In recent years, laser wood processing has become increasingly common. However, to ensure the longevity of wooden materials, it is necessary to cover their upper surfaces. This study investigates the effects of laser beam-induced changes on various preferred types of wood surface treatments using CNC laser wood processing technology. Beech wood test specimens were coated with cellulosic varnish, synthetic varnish, polyurethane varnish, and acrylic varnish and their layer thickness was measured. Based on the data obtained, it was evaluated how different varnish layers affect kerf depth and upper kerf width in laser cutting compared to control samples without varnish. Additionally, the impact of varnish layers on laser wood engraving was examined. The findings suggest that certain varnishes can compromise the laser cutting performance of the control samples, while others can enhance it. Furthermore, all varnish types positively influence laser cutting performance by reducing the upper kerf width of the laser cutting notches. However, in laser wood engraving, all varnish types weaken the laser engraving performance.

The effectiveness of the impregnation process depends mostly on the treatability of wood species, along with the type and properties of impregnating agents. The treatability of wood is an essential factor, as it significantly affects the liquid flow path during the impregnation process. Unlike softwood, hardwood has more complexity concerning the liquid flow path due to the diversity of cells and their interconnections. Different impregnating agents result in different phenomena, which are interesting to investigate. Three hardwood species native to Indonesia, namely sepetir (Sindora spp.), pisang putih (Mezzettia spp.), and nyatoh (Palaquium spp.), were utilized and compared in an identical treatment. The impregnation process was carried out by vacuum-pressure and then followed by a hot immersion process in each water-soluble impregnating agent, namely the low molecular weight of phenol formaldehyde (LMW-PF), polyethylene glycol (PEG), and succinic anhydride (SA). Results showed that the treatability of wood during the impregnation process is more likely to be influenced by its oven-dry (OD) density. Sepetir, which has a lower OD density, takes up more impregnating agents and produces higher dimensional stability compared with other wood species. PEG and SA treatments result in higher treatability and dimensional stability; however, they are only suitable for short-term periods due to their weak bonding efficiency within the wood structure, causing some release of those compounds during the soaking-drying process. Even though LMW-PF treatment has lower treatability, as indicated by its lower impregnation uptakes, it can produce comparable dimensional stability with a lower leaching rate.

There is growing interest recently in reducing the usage of metals in timber structures. Birch plywood possesses satisfactory mechanical properties compared to other wood-based panels and is promising to be utilized in timber connections as a substitute for the more conventional slotted-in metal plate. There are essentially two possibilities to connect plywood plates and other timber elements by means of either mechanical connections or adhesively bonded connections. Despite the more commonly adopted mechanical connections in current timber structures, the adhesively bonded connections hold the distinct advantages of being more cost-effective, stiffer, and with a lower risk of moisture penetration in the timber elements. When employing birch plywood in timber structure applications such as trusses and frame corners, stresses from different directions need to be transmitted by the plywood gusset plate. However, it is still uncertain how the bonding strength is affected by different loading angles to the face grain. This research question, specifically concerning the bonding strength between birch plywood and spruce glulam, has been addressed in this paper. It was found that the bonding strength varies within a relatively small range when the load-to-plywood face grain angle varies from 0° to 90°, which is promising for the development of adhesively bonded joints. Failure mainly occurred in glulam at 0° and 15°; while at other angles, a mixture of cohesive failure in glulam and plywood face veneer was dominant. The weak angle-dependence of the bonding strength can be explained by further checking the shear strength of the weaker wood adherends between glulam and plywood. A strong positive correlation was observed between bonding strength and the wood shear strength.