School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemEffects of mat composition and pressing time on citric acid-bonded ultra-low-density hemp hurd particleboard(Elsevier, 2024-04-01)This study investigated the feasibility of using citric acid (CA) as a biobased and formaldehyde-free binder for producing ultra-low-density (320 to 338 kg/m3) hemp hurd particleboard (ULHPB). Mechanically decorticated hemp hurd chips were milled and then separated into fine (F), medium (M), and coarse (C) particle sizes. Three particle size mixes (PSM) were used to fabricate the panels: 100% C, 100% M, and a 50/50% mixture of CM. Each PSM was combined with low and high CA contents (20 and 30 wt%) and subjected to short and long pressing times (8 and 12 min) at 200 °C. Physico-mechanical characteristics were evaluated following Australian standard AS/NZS 1859.1 (2017) for reconstituted wood-based panels. Thermo-chemical analyses were performed to understand the properties of the raw hurd and to investigate the binding mechanisms in CA-ULHPB. The PSM had a significant impact on panel expansion (springback), internal bond strength (IB), water absorption (WA), and thickness swelling (TS) in most CA-ULHPB variants. PSM-C panels exhibited superior IB when pressed with 30 wt% CA for 12 min. The effect of PSMs diminished for WA and TS but CA content and pressing time remained highly significant. Py-GC/MS, FTIR spectroscopy and TGA indicated the formation of ester linkages with carbohydrate-derived OH-groups and the involvement of lignin moieties in the CA-ULHPB. This research identified optimal panel compositions and processing parameters for fabricating environmentally friendly composite panels using CA as a natural adhesive and hemp hurd as an agricultural by-product. The panels exhibited excellent properties and would be well suited as core layers in lightweight sandwich composites given their ultra-low-density range.
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ItemGluing characteristics of Papua New Guinea timber species for various non-structural applications(Universidad del Bío-Bío, 2023)Papua New Guinea (PNG) has abundant natural forest resources but there are many constraints which need to be addressed to support the development of competitive value-added wood industries. There is a need to develop knowledge and capacity in wood science and processing technologies which support successful domestic value-adding wood processing enterprises. A comprehensive testing program has been developed to assess the glue‐bond strength and performance of selected commercial PNG timber species in various climatic conditions to simulate service conditions in potential market destinations. Two criteria namely shear strength and wood failure have been used to determine if a species can meet the minimum requirements for either dry use or wet use applications. The performance of 24 different PNG commercial timber species has been assessed using a one-component cross-linking polyvinyl acetate emulsion adhesive. The bondability of the selected species has been carefully estimated considering the wood density and wood moisture content for the strength and durability in dry- and wet-use conditions. The testing results show that as the wood density as a wood property factor and moisture content as a service condition factor increase, high shear strength with high wood failure become more difficult to achieve consistently. The highest shear strength and wood failure results were achieved by softwood plantation species and low-density hardwood species. Based on the testing results, the selected species have been classified into bondability classes (bond very well, bond well, bond with difficulty, very difficult to bond).
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ItemInfluence of particle granulometry and panel composition on the physico-mechanical properties of ultra-low-density hemp hurd particleboard(Wiley, 2023)This study investigated Australian hemp hurd (Cannabis sativa L., “Frog One”) as a lignocellulosic raw material for ultra-low-density hemp particleboard (ULHPB) with densities ranging from 213 to 309 kg/m3. The hurd was first milled and fractionated into three particle size categories, that is, fine (F), medium (M), and coarse (C). Twelve unique ULHPB variants were then fabricated comprising varying particle loadings from four particle size mixes, that is, 100% C, 100% M, 50%/50% CM, 25%/50%/25% CMF, and adhesive contents of bio-epoxy (EPX), phenol resorcinol formaldehyde (PRF), and emulsifiable methylene diphenyl diisocyanate (MDI), respectively. The panel assessments, conducted in accordance with the Australian reconstituted wood-based panels standard AS/NZS 1859.1 (2017), revealed a significant effect of particle dimension on most physico-mechanical properties. Furthermore, the resination method and pressing temperature controlled post-cure panel expansion and additional panel characteristics. Notably, MDI-ULHPB exhibited drastically different behavior and properties compared to EPX and PRF equivalents, demonstrating greater bending strength, stiffness, screw withdrawal strength, and dimensional stability. Importantly, all MDI variants conformed to the 15% thickness swelling limit for moisture resistant particleboard. Surface lamination of MDI-bonded ULHPB with sheets of aluminum, Masonite, and Kraft liner significantly improved the inherently low flexural properties, suggesting the potential suitability of ULHPB as a core layer in lightweight sandwich composite panels. The integration of agricultural by-products, such as hemp hurd, into engineered building materials presents a promising opportunity to mitigate the depletion of finite timber resources and aligns well with circular economy principles. Highlights • Utilizing agricultural residue as sustainable raw material in building products. • Hemp hurd enables ultra-low-density particleboard with thermosetting resins. • Coarse particle size mix enhances mechanical performance in panels. • Panel characteristics controlled by resination method and pressing temperature. • Lamination enhances functionality of lightweight hemp hurd sandwich panel.
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ItemAn investigation on peeling recovery and quality of senile plantation-grown rubber trees in Laos(Springer (part of Springer Nature), 2020)The study assessed the peeling potential of rubber trees past the prime latex-producing age when the latex yields become non-economical. Fifteen 25-year-old plantation-grown trees were harvested and peeled using spindleless lathe technology. Following peeling, veneer sheets were measured and graded to determine volume and quality recoveries. Relationships between billet characteristics and recoveries or quality were examined and a recovery predictive model proposed. Most of the main causes identified for downgrading face veneers were either processing-related issues or drying-induced defects. Thus, a combination of several optimisation techniques could annihilate most of the main causes of downgrading veneer, potentially leading to a substantial proportion of higher-quality veneers typically used where surface decorative appearance is a primary consideration. The results demonstrated that rubber trees past their latex-producing prime from unthinned and unpruned stands have qualities and desirable traits to potentially produce certain high-value engineered wood products. Senile rubber trees in Laos could represent significant additional revenue to growers and a source of raw material to the industry which, theoretically, could be converted into high-value products if other factors can be overcome.
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ItemTimber Trading and Pricing of Plantation Grown Teak (Tectona grandis Linn.F) in Laos(SPRINGER, 2021-12)The market demand and price of teak in Laos vary broadly and depend on several factors. The aim of this study was to assess timber trading and pricing based on a survey of teak buyers. The research investigated teak trading methods, markets and prices paid for particular timber types and quality grades. Three types of teak timber are commonly sold: 24.7% as standing trees, 39.6% as round logs and 35.7% as square logs. The main wood products produced from plantation teak include joinery products, door and window frames, and furniture (57.9%, 26.3% and 15.8% respectively). The end buyers of teak timber in Laos are sawmillers and wood manufacturer. Teak timbers supplied to end buyers from growers via the local traders account for 49.0%, followed by 41.3% by direct supply from teak growers and 9.7% via the local small sawmillers and wood manufacturers. The price of teak timber varies significantly based on four main factors: timber types, log sizes, log quality (grades) and distance from plantation site to road (for standing trees). The round log price of 250US$/m3, based on both log diameter size (D26-30 cm) and log quality grade (A grade), was much lower than the 321US$/m3 amount paid for the same size of round log (D26-30 cm) based on log diameter alone (no grading price). It can be concluded that there is a need to develop a clear system or standard for teak log grading and pricing in Laos.
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ItemPlaning characteristics of Papua New Guinea timber species from plantations and regrowth forests(SPRINGER, 2020-03)Although Papua New Guinea (PNG) has a rich and diverse forest cover, there is limited information on processing characteristics for plantations and regrowth forests available. Consequently, the PNG timber processing industry is restricted to a few species, producing low-quality products, which limits opportunities for the processors. Sound knowledge of machining characteristics based on some systematic methods has been identified as essential for assessing the ability in processing raw material into appearance products. Therefore, a testing program was conducted to assess the planing characteristics and most common causes for planing degrade of 25 species sourced from the Morobe and West New Britain provinces, PNG. A total of 18 wood species proved to machine very well with more than 90% of assessed boards being graded either “excellent and requiring very light sanding” or “good and requiring light sanding”. Eight species from this group obtained a perfect score, i.e. requiring very light sanding.
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ItemASSESSMENT OF PHYSICAL AND MECHANICAL PROPERTIES OF PAPUA NEW GUINEA TIMBER SPECIES(UNIV BIO-BIO, 2020-01)A comprehensive testing program has been developed to assess different physical and mechanical properties of 26 commercial and lesser-known PNG species from secondary and plantation forests. The impact of log position in a tree on the mechanical properties has also been assessed to optimize the utilization of timbers along the value chain. The results showed that stiffness and bending strength tend to decrease or remain unchanged along the stem. Shear strength and Janka hardness displayed a similar trend to a lesser extent where the position in the tree had a limited impact on compression strength properties. Thus, segregating based on log position can be of interest where desired mechanical properties and costs associated with segregating justify optimum mechanical properties for the intended end use. The properties of selected species from plantations and regrowth forests were generally lower than those found in the literature for timbers from old-growth forests. The size of specimens tested, the amount and provenance of tested material, and some adaptive traits for tropical tree species are some factors potentially explaining observed differences. However, a comparison with recent studies tends to confirm the overall reduction of physical and mechanical properties when compared with old-growth forests timbers.
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ItemA Wood Recovery Assessment Method Comparison between Batch and Cellular Production Systems in the Furniture Industry(AMER SOC TESTING MATERIALS, 2019)Abstract Enhanced wood recovery mirrors a successful wood manufacturing operation. Studies of wood recovery in secondary wood processing, however, are scarce, particularly in furniture manufacturing. Although recovery rates are under the continuous surveillance of sophisticated technology, this attempt to monitor wood recovery would be especially challenging for small- to medium-sized furniture enterprises, as the capital investment in such technology would be substantial. This would hinder the possibility for improvements in production efficiency of the furniture industry. A methodology of wood recovery assessment in the furniture industry has been developed and proposed but has not been validated with a cellular production system, a different layout process and distinctive machinery, species, and other customer requirements. The objective of this study is to assess the wood recovery protocol individually used in batch and cellular production systems, followed by examining the wood recovery of furniture manufacturing in these distinct production systems. Two Indonesian medium-sized furniture companies that individually operate batch and cellular production systems were employed, and two methods, mass and volume, were used to assess wood recovery at each furniture-making station. There was a significant difference in cumulative wood recovery rates between batch and cellular production systems. Based on species and product dimensions, the average individual and cumulative wood recovery rates of furniture manufacturing resulted in a significant difference at the resawing and edging station. Large-dimension product recorded higher wood recovery level than small-dimension product. The wood recovery rates at the resawing and edging, surface planing, thickness planing, and trimming stations were mostly influenced by species, the quality of sawn timber, and cutting bills. Meanwhile, wood recovery at other stations was affected by product dimension and design. The mass method was the most acceptable method according to the measurement systems analysis.
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ItemFurniture Production Efficiency in the Indonesian Context(International Conference on Wood Science and Technology, 2018-10-16)Most efficiency improvement strategies implemented in furniture manufacturing are data-driven methods. Due to a lack of production systems used in most Indonesian small and medium-sized furniture companies, the evaluation of production efficiency for future improvement seems rather difficult to perform. A wide range of existing evaluation tools and the varying capabilities of the companies to adapt the methods contribute to a problematic evaluation process. Research has been undertaken with the aim to develop a generic efficiency evaluation method and to prioritise a new potential metric to assess and control efficiency in furniture manufacturing. A basic production cost analysis with standardized variables has been demonstrated as a typical method to evaluate production efficiency in multi furniture companies, followed by applying a wood recovery assessment, a Pareto analysis, an X-Y matrix, and process capability analysis. The heartwood proportion of teak (Tectona grandis) has been determined as a key potential efficiency metric to control and monitor teak sawn board quality and its utilisation. Applying process capability analysis with a setting of lower specification limits to the population of teak heartwood rates produces a model to simulate optimal teak utilisation.
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ItemQuality assessment of the drying process for Eucalyptus delegatensis timber using greenhouse solar drying technology(Springer Verlag, 2019-01-24)The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) during day time were set at 430C/72% RH. In the night time the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).