Abstract
This study investigated the effects of different citric acid content on the physico-mechanical and biological durability of rubberwood particleboard. Particleboards with density of 700 kg/m3 were produced with three different citric acid contents, namely 10, 15 and 20 wt%. Particleboards made from 10 wt% urea formaldehyde (UF) resin were served as control for comparison purposes. FTIR analysis was carried out and the formation of ester linkages between -OH on cellulose and carbonyl groups of citric acid was confirmed. The peak intensity increased along with increasing citric content, which indicated that a higher amount of ester linkages were formed at higher citric acid content. Citric acid-bonded particleboard had inferior physical properties (water absorption and thickness swelling) and mechanical properties (internal bonding strength, modulus of rupture and modulus of elasticity) compared to that of the UF-bonded particleboard. However, the performance of particleboard was enhanced with increasing citric acid content. Meanwhile, citric acid-bonded particleboard displayed significantly better fungal and termite resistance than UF-bonded particleboard owing to the acidic nature of citric acid. It can be concluded that citric acid is a suitable green binder for particleboard but some improvement is needed during the particleboard production process.
Highlights
Citric acid has been identified as an environmentally friendly treating agent and adhesive for wood and wood composites
Rubberwood particles were obtained from HeveaBoard Berhad, a particleboard manufacturer located in Gemas, Negeri Sembilan
Similar observation was found at absorption peak near 1042 cm−1 which belongs to C–O stretching in cellulose I and cellulose II [12]
Summary
Citric acid has been identified as an environmentally friendly treating agent and adhesive for wood and wood composites. Citric acid has been used in treating wood in order to confer the wood with better dimensional stability and biological durability [1,2]. Sefc et al (2009) reported that beech (Fagus sylvatica L.) wood modified with 7.0% citric acid (CA) and 6.5% sodium hypophosphyte (SHP) as catalyst have higher resistance against brown rot fungus, Poria placenta. The resistance enhancement of citric acid modified beech wood could be attributed to the ester bonds between CA and beech wood [3]. Apart from enhanced dimensional stability and biology durability, wood modified with citric acid displayed improved modulus of elasticity (MOE) and compression strength and reduced water absorption [5]. Some drawbacks were recorded, including reduction in both modulus of rupture and impact strength as well as the unfavourable yellowing after treatment [5]
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