No abstract

In this study, the effect of superheated steam (SHS) treatment on the changes of the chemical composition and biological properties of two tropical hardwoods was investigated. SHS was carried out on light red meranti (Shorea spp.) and kedondong (Canarium spp.) wood with dimensions of 410 × 25 × 25 mm, using superheated steam as the heating medium. Wood samples were heat-treated at nine treatment levels, ranging from 172 to 228 °C and 95 to 265 min, respectively. The chemical constituents and resistance against white rot fungus (Pycnoporus sanguineus) and subterranean termite (Coptotermus curvignathus) of the treated wood were evaluated. A significant reduction in holocellulose content and increment in lignin was observed after SHS treatment. Consequently, the resistance against white rot fungus and termites improved. The biological durability improved with an increasing treatment temperature and time. A regression analysis revealed that the reduced equilibrium moisture content imparted superior biological resistance to the treated wood. Weight loss caused by the thermal degradation also served as a good indicator for fungal decay, as the loss of weight was directly proportional to the improvement in fungal resistance. However, this did not apply to termite resistance, as a very weak relationship was found between the two variables.

The peeling of small-diameter rubberwood logs from the current short-rotation practices undoubtedly will produce lower grade veneers compared to the veneers from conventional planting rotation. Hence, this raises the question of the properties of the produced laminated veneer lumber (LVL) from veneers peeled from small-diameter rubberwood logs using the spindleless lathe technology. Different thicknesses of rubberwood veneers was peeled from rubberwood logs with diameter less than 20 cm using a spindleless lathe. Three-layer LVLs were prepared using phenol formaldehyde (PF) adhesive and hot pressed at different temperatures. During the peeling of veneer, lathe checks as deep as 30–60% of the veneer thickness are formed. Owing to deeper lathe check on 3 mm rubberwood veneer, higher pressing temperature significantly increased the gluebond shear strength of the PF-bonded LVL. In addition, lathe check frequency was also shown to influence the bond strength. The presence of higher lathe check frequency on 2 mm veneer increased the wettability, thus facilitating optimum penetration of adhesive for stronger bonding. These findings stress the importance of measuring and considering the lathe check depth and frequency during the lamination process to get a better understanding of bonding quality in veneer-based products.

Bamboo requires treatment to extend its service life. However, as bamboo strips could serve as a suitable candidate for lamination, the treatment may affect its bendability. The current study investigated the effects of boric acid treatment on the physical, mechanical, adhesion, and morphological properties of bamboo strips. Owing to their availability and popularity in local industries, four Malaysian bamboo species were used in this study, namely Gigantochloa scortechinii, Gigantochloa levis, Dendrocalamus asper, and Bambusa vulgaris. These four species’ bamboo strips were treated with 5% boric acid and their properties were evaluated. The findings revealed that the boric acid treatment had varying degrees of effect on the properties of the bamboo. Despite having lower treatability and stability, both G. scortechinii and G. levis have greatly superior mechanical properties that justify their use in the production of laminated products. The boric acid treatment was found to provide several benefits to bamboo strips intended for lamination, including increased wettability, dimensional stability, and mechanical strength.

Eucalyptus hybrid has been planted rigorously in wet tropical regions including Malaysia. Recently, there was a report on the occurrence of stem canker on these trees. However, the extent of the infections by this stem canker is unknown. The aim of this study was to evaluate the influence of stem canker disease, Chrysoporthe deuterocubensis, on the physical and mechanical properties of 11-year-old E. urophylla × E. grandis or also known as E. urograndis. The samples were taken from infected and healthy trees that were segregated into different classes based on the severity of the attack, i.e., healthy (class 1), moderately infected (class 2), severely infected (class 3) and very severely infected (class 4). A total of 1440 samples from four infection classes were used in this study. The physical and mechanical properties were determined according to the standard test procedures specified by the International Organization for Standardization (ISO) 13061:2014 (Parts 1 to 4, 13, 14 and 17) and British Standard (BS 373: 1957). From the result, a significant effect by the infection classes was observed on physical and mechanical properties of E. urograndis. All infected wood experienced less shrinkage compared to that of a healthy one, particularly the volumetric (Volsh) and radial shrinkage (Rsh). Wood from class 2 and class 3 was less affected by the infection while the majority of wood from class 4 had significantly lower density and poorer strength. Based on the strength data, wood from infection class 2 can be considered to be used for non-structural applications such as furniture, interior finishing, window frames and doors since reduction in mechanical properties was observed. Wood from class 3 would need further investigation to examine its suitability for structural applications.