Properties of medium-density particleboard from saline Athel wood

https://doi.org/10.1016/j.indcrop.2005.09.003Get rights and content

Abstract

The Athel tree, Tamarix aphylla (L), can potentially be used as a biomass crop to help manage saline subsurface drainage water in arid land irrigated agriculture. In this study, Athel wood was used to manufacture medium-density particleboard with an aim of developing new applications for the saline wood. The research investigated the effects of different types of adhesives, particle sizes, bark content (BC), resin content (RC), and hot water pretreatment on the mechanical and water resistance properties of the Athel-derived, medium-density particleboards. The measured mechanical properties included tensile strength (TS), modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength (IB) of the finished particleboards. Water absorption and thickness swell were used to evaluate the water resistance. Polymeric methane diphenyl diisocyanate (PMDI) resin made particleboard of better mechanical properties and water resistance than urea formaldehyde (UF). The medium size (20–40 mesh) particles gave the best mechanical properties and water resistance than of the particleboard when evaluated against the smaller size (40–60 mesh) and larger size (10–20 mesh) particles. The mechanical properties of particleboard were improved as the resin content of the UF-board increased from 7 to 16%, but deteriorated as the bark content increased from 0 to 16.2%. The particleboard made from the wood particles that had undergone hot water pretreatment had poor mechanical properties and water resistance compared with the particleboard made from the untreated particles. Saline Athel wood is an appropriate material for manufacturing particleboards.

Introduction

The demand for composite wood products, such as plywood, oriented strandboard (OSB), hardboard, particleboard, medium-density fiberboard, and veneer board products has recently increased substantially throughout the world (Youngquist, 1999, Sellers, 2000). According to a report from Food and Agricultural Organization (FAO) of the United Nations, the worldwide demand of particleboard panels was 56.2 Mm3 in 1998 (Youngquist and Hamilton, 2000). The demand for particleboards in the sectors of housing construction and furniture manufacturing has continued to increase (Sellers, 2000). In North America, 76 particleboard mills produced 10.952 Mm3 in 1998, accounting for 19% of the total wood composites produced (Sellers, 2000, Sellers, 2001).

The feasibility of using fast-growing trees and agricultural residues as raw materials for particleboard production has been explored by a number of researchers. Nemli et al. (2004) reported that the overall strength property and water resistance of the wood composites made from black locust (Robibia pseudoacacia L.) were comparable to those of mature wood composites and better than European Standard for Particleboard (ESC, 1996a, ESC, 1996b, ESC, 1996c, ESC, 1996d). Pugel et al., 1989, Pugel et al., 1990 reported that the overall strength property and water resistance of the wood composite made from southern pine (Dendroctonus frontalis Z.) juvenile trees were similar to or better than those of mature wood composites. Red pine (Pinus resinosa) thinning had similar properties to aspen when it was used as a raw material for laboratory waferboards bond with phenolic resin (Li et al., 1991). Oh et al. (2003) determined the effect of four different wood types (Pinus rigida Miller, Pinus densiflora Sieb. et Zucc., Larix leptolepis Gordon and Quercus acutisstima Carruthers) on the properties of particleboards and reported that all wood types can potentially be used to produce acceptable wood composites.

The Athel tree is an introduced, fast-growing, evergreen tree that grows in southwestern United States including California (Baum, 1967). It is drought resistant and tolerant of alkaline and saline soils and grows along irrigation ditches in the bottomlands (Little, 1980, Benson and Darrow, 1981). It has been found along the saline portions of the lower Colorado and Gila rivers and in the Salton Sea Basin (Turner and Brown, 1982). The Athel also grows on salt flats, springs, and other saline habitats especially along streams and rivers (Powell, 1988). The Athel trees can absorb and concentrate some salt in the wood as growth nutrients (Simpfendorfer, 1989). In the San Joaquin Valley (SJV) of California, the Athel trees have been grown and used for removing water by transporting and concentrating salts from agricultural drainage water. Usually, the Athel wood is used for fuel because it produces a fragrant odor when burned. It has been proposed for use in making furniture and fence posts (Little, 1980, Benson and Darrow, 1981, Mozingo, 1987). New applications of its wood need to be developed before Athel can become an economically viable tree species for use in soil and water remediation.

In addition, Athel has high ash (30–40%) and salt content, making it difficult to burn even when it is dry (Simpfendorfer, 1989). This indicates that the Athel-based particleboard could have superior fire retardant and other beneficial characteristics. Silica, phenol and some oxidants, including CuO, CrO3, and As2O5 have been reported to have significant effects on improving the mechanical properties, water resistance properties, and decay resistance of particleboard (Huang and Cooper, 2000, Clausen et al., 2001, Zhou and Kamden, 2002, Nemli et al., 2004). However, no literature has been found on the feasibility of using saline Athel as a raw material for particleboard.

The objectives of this research were to (1) characterize the mechanical properties and water resistance of medium-density particleboards made from Athel as affected by adhesive type, wood particle size, bark content (BC), resin content (RC) and hot water pretreatment, (2) study the effect of moisture content (MC) and BC on the pH value of wood particles, and (3) determine the relationship between relative humidity (RH) and equilibrium moisture content (EMC) of the finished particleboards.

Section snippets

Materials

Urea formaldehyde (UF) resin (C-TH39, 65.6% solid content) and polymeric methane diphenyl diisocyanate (PMDI) (100% solid content) were used as the adhesives for making the particleboards. UF was obtained from Borden Chemical Company (Hope, AR) and PMDI from Bayer Polymers LLC. (Pittsburgh, PA). Ammonium sulfate was purchased from Fisher Scientific Chemical Co. (Fair Lawn, New Jersey) and was used as the curing agent for the UF resin.

The Athel wood from 8 years old trees was collected from the

Effect of particle size on particleboard properties

When the wood particles of three different sizes were used to make particleboards, the 20–40 mesh size resulted in the highest MOR, TS, and IB values although there were no significant differences between the 10–20 mesh and 20–40 mesh for MOE, TS, and IB (Table 1). The 20–40 mesh particles were probably covered better by the resin and may have had better bonds based on the observed structure. However, the 40–60 mesh particles had the lowest mechanical properties. This may be due to the fact that the

Conclusions

The results of this study indicate that saline Athel wood is a suitable raw material for making particleboards. High quality particleboards were obtained by using wood particles of 20–40 mesh. The particleboards made with PMDI at 4% RC had better product quality than the particleboards made with UF at 7% RC. If water resistance is important for the applications of the particleboards, PMDI appears to be the preferred adhesive even though its cost could be higher than UF. When UF was used, the

Acknowledgements

The authors thank the California Department of Water Resources for providing partial funding support and the Red Rock Ranch Farm for providing the raw materials for this research.

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