Abstract
Wood particles and a mixture of forest waste were investigated as raw material for the particleboard industry. Urea formaldehyde resin was used as the adhesive in the production of the particleboards. Some chemical (pH, dilute alkali solubility, hot and cold water solubility), physical (density, moisture, thickness swelling, and water absorption), mechanical (modulus of rupture, modulus of elasticity, internal bond strength, and screw holding strength) properties, as well as the contact angle values of the resulting particleboards were determined. Due to its needle litter and cone content, the forest waste exhibited a lower pH value and a higher content of extractive material than wood. Increasing the addition of forest waste led to significant reductions in the physical and mechanical properties of the particleboards. The addition of forest waste reduced the internal bond strength the most (56.6%), whereas the least reduction (15.7%) was in the value of screw holding strength perpendicular to the surface. The values of all panels except panel type F exceeded the minimum modulus of elasticity (1600 N mm-2) required for furniture production according to the EN 312-P2 standard. Results of the analyses showed that forest waste (10% and 20%) is a suitable renewable raw material source for panel production.
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The Potential of Using Forest Waste as a Raw Material in Particleboard Manufacturing
Halil İbrahim Şahin *
Wood particles and a mixture of forest waste were investigated as raw material for the particleboard industry. Urea formaldehyde resin was used as the adhesive in the production of the particleboards. Some chemical (pH, dilute alkali solubility, hot and cold water solubility), physical (density, moisture, thickness swelling, and water absorption), mechanical (modulus of rupture, modulus of elasticity, internal bond strength, and screw holding strength) properties, as well as the contact angle values of the resulting particleboards were determined. Due to its needle litter and cone content, the forest waste exhibited a lower pH value and a higher content of extractive material than wood. Increasing the addition of forest waste led to significant reductions in the physical and mechanical properties of the particleboards. The addition of forest waste reduced the internal bond strength the most (56.6%), whereas the least reduction (15.7%) was in the value of screw holding strength perpendicular to the surface. The values of all panels except panel type F exceeded the minimum modulus of elasticity (1600 N mm-2) required for furniture production according to the EN 312-P2 standard. Results of the analyses showed that forest waste (10% and 20%) is a suitable renewable raw material source for panel production.
Keywords: Contact angle; Forest waste; Wood particles; Particleboard; Urea formaldehyde
Contact information: Department of Forest Industry Engineering, Faculty of Forestry, Duzce University, Duzce, Turkey; *Corresponding author: halilibrahimsahin@duzce.edu.tr;hisahin61@gmail.com
INTRODUCTION
The growing population, new usage areas, and technological developments are boosting particleboard consumption at a rapid pace. According to the Food and Agriculture Organization (FAO) 2018 statistical data, particleboard produced in Turkey amounts to 4,286,000 m3. With this production amount, Turkey ranks fifth in the world and is the fourth largest particleboard manufacturer in Europe. Turkey, with a medium and high density fiberboard (MDF/HDF) production of 4,747 million m3, ranks second after China in the world market. With this amount of production, it is the leader in the European market. Moreover, according to FAO data for 2016, Turkey, at 10 million m3, is the fifth largest consumer country of wood-based panels (FAO 2016). In terms of these data, new production resource alternatives to wood, as the main raw material of the panel industry (particleboard, MDF, HDF, OSB, etc.), will play an important role in reducing the pressure on Turkey’s forests.
According to Turkey’s General Directorate of Forestry data for 2015, the forest assets in Turkey amount to 22.3 million ha. The forest growing stock is 1.6 billion m3. Of this stock, 33% is broad-leaved forest (oak, beech, alder, chestnut, hornbeam, etc.), 48% is coniferous forest (Calabrian pine, black pine, Scots pine, fir, spruce, cedar, etc.), and the remaining 19% consists of mixed coniferous and broad-leaved forest. In terms of the distribution area of the tree species, oak shows the highest distribution with 5.9 million ha, followed by, according to the size of the area, Calabrian pine (5.6 million ha), black pine (2.7 million ha), beech (1.6 million ha), Scots pine, juniper, fir, cedar, spruce, stone pine, alder, chestnut, hornbeam, poplar, linden, ash, and eucalyptus (Orman Genel Müdürlüğü 2015). Almost all of these species have widespread uses in the forest products industry. Total biomass yield and leaf ratio vary according to the species and variety. Climate (moisture and solar radiation) and soil quality are the determining factors on biomass efficiency. The fresh leaf yield for some species in Turkey has been reported to be 27 ton/ha/year for oak tree leaves, although it changes depending on the diameter, and 4 to 11 ton/ha/year for Scots pine needles (Durkaya 1998; Ülker 2010).
The panel industry mainly uses different wood species as raw material. Raw material wood constitutes a significant part of total panel production costs. Alternative raw materials obtained from agricultural and forestry wastes are important natural resources for the panel industry because they are cheaper (Bektas et al. 2005; Şahin et al. 2017). In the production of particleboard and MDF, different lignocellulosic wastes can be mixed with wood or as a direct alternative raw material to wood (Guler et al. 2016; Gokdai et al. 2017; Kowaluk et al. 2020). Youngquist et al. (1994) found over 1000 research reports related to the use of non-wood plant fibers as building materials and for panel production. If alternative raw material sources to wood are to be used in the wood-based panel industry in the future, these materials must display properties equivalent to or better than those of wood.
While many developed countries in the world are evaluating agricultural waste fibers for production of composite panels, Turkey uses wood as a source of raw material in the production of composite boards (particleboard, fiberboard, plywood, etc.). The lignocellulosic forest wastes (FW) to be added to the panel production will contribute to the use of raw material wood resources more rationally, economically, and in accordance with its purpose. In our country, approximately 40 to 45% of the wood and chips that are the raw material source of the panel industry can be obtained by importing them from other countries. In order to meet rapidly increasing production and consumption demands, the use of different raw materials is inevitable. For this purpose, many lignocellulosic raw materials have been used for the production of particleboard, including vine stems (Yeniocak et al. 2014), kenaf stem (Juliana et al. 2014), waste tea leaves (Batiancela et al. 2014), cotton stalk (Nazerian et al. 2016), flax chips (Sam-Brew and Smith 2017), corn stalk (Guler et al. 2016), sunflower stalk (Klimek et al. 2016), coir pith (Ahmed et al. 2016), poppy husk (Küçüktüvek et al. 2017), rice husk and bamboo stalk (De Melo et al. 2015), tobacco stalk (Acda and Cabangon 2013), rape straw (Dziurka et al. 2015), banana skins (Papadopoulos 2018), palm branches (Amirou et al. 2013), and reed stems (Kord et al. 2015).
Some studies have shown that if the forest and agricultural wastes are used in the particle board industry, the boards can be suitable based on EN standards. Pirayesh et al. (2015) investigated some physical (thickness swelling and water absorption) and mechanical (modulus of rupture, modulus of elasticity, internal bond strength) properties that were determined for particleboard produced with a mixture of maple leaves and wood chips. Panels were produced from five different wood-leaf mixtures (100/0, 90/10, 80/20, 70/30, and 60/40). The analyses showed that the physical and mechanical properties had been improved with up to 20% leaves, and all the panels produced met the EN standards required for furniture production. In addition, the use of sycamore leaf as a renewable biomaterial in particleboard production has been reported to reduce pressure on forests as well as contributing to the efficient utilization of the raw material.
Klimek et al. (2018) produced particleboards with a density of 0.60 g cm-3 and a thickness of 11 mm, using MDI resin in different proportions (4% and 6%) with spruce chips and miscanthus stalks. A 30% decrease in modulus of rupture and modulus of elasticity values and a 60% reduction in internal bond strength were found in panels using the annual plant stalks compared to particleboards made from spruce chips. This was directly related to cell collapse occurring in the parenchyma cells of the annual plants.
Another study investigated the suitability of walnut/almond shell, a renewable agricultural waste, for the production of wood-based panels. Using urea formaldehyde adhesive, particleboards were produced with different amounts (0%, 10%, 20%, 30%, and 100%) of walnut/almond shell. Some physical and mechanical properties and the formaldehyde emission values of the panels were determined. There were significant improvements in the water resistance of the boards with the addition of walnut/almond shell particles, while formaldehyde emissions were reduced to a large extent. The decreases in the mechanical properties were determined. In this study, it was stated that because of the low water absorption, thickness swelling, and formaldehyde emission rate, walnut/almond shells could be used as an alternative raw material or filler for the production of wood-based particleboards for indoor use (Pirayesh et al. 2013).
Developing value-added products from underutilized lignocellulosic biomass is an important opportunity for Turkey’s forest resource management as well as for local economic development. From this point of view, the aim of this study was to use pine needle litter and broad-leaf that has no use, and pine cones, that are generally used as fuel or for their seeds, as alternative raw material in the particleboard industry.
EXPERIMENTAL
Materials
The pine needle litter, broad-leaf (oak and hornbeam, mixed) and cones (black pine and Scots pine, mixed) used in the production of the panels were obtained from the Kastamonu and Sinop regions in Turkey. The impurities (stones, soil, twigs, etc.) were removed. The cones were opened and the seeds removed. Afterwards, each sample was chipped separately in a Willey mill and placed in a bag. The forest wastes (FW) and wood particles (WP) are presented in Fig. 1a-c.
Methods
Production of test panels
The FW provided for the experimental study were mixed with WP for use in the core layer of the particleboards. Taking this situation into consideration, a two-stage sieving was carried out to render the FW suitable for particleboard production. Samples were first classified using 10.5 × 10.5 mm mesh sieves in accordance with industrial factory production. Waste remaining on the sieve was removed. The particles passed through these sieves were then reclassified in 2.1 and 0.7 mm sieves and the wood, leaf and cone particles remaining on the sieve were classified separately for use in the core and surface layers of the particleboards, respectively.