Biocomposite boards from wheat straw without addition of bonding agent

Abstract

The present paper reports work in development of biocomposite boards compression moulded from wheat straw. Unlike most traditional wood based fibre/chip boards with addition of adhesives or bonding agents, attempt was made to utilise the lignin-hemicellulosic natural resin within straw as bonding agent, resulting in a class of 'binderless' and more natural biocomposite boards. The effects of straw preparation and compression moulding conditions on structural and mechanical properties of the binderless straw boards were studied systematically in terms of size of chopped straw, pretreatment and the combination of pressure and temperature during compression moulding. The bonding mechanisms of the natural resin in the straw biocomposites were investigated in terms of its mobilisation using NaOH pretreatment of straw and its redistribution to the straw interfaces during compression moulding process. Without any fractionation of straw or any additional adhesive bonding agent, the mechanical properties of the binderless straw boards were comparable to some commercially available wood and straw board products using addition of adhesives.

The role of lignin in wood working processes using elevated temperatures: an abbreviated literature survey

“…Due to its environmentally friendly properties, many researchers tried to produce fiber or particle boards without adhesive or using bio-based adhesives such as sugars or lignin. Wood-based binderless fibreboards without synthetic resin binders have been produced for at least 80 years: several types of bio-raw material were used for binderless boards, for example wood bark (Chow 1975;Wellons and Krahmer 1973;Geng et al 2006;Gao et al 2011), rice and wheat straw (Zhao et al 2013;Kurokochi and Sato 2015a, b), kenaf (Xu et al 2004), banana stems (Nongman et al 2016), coconut husks (van Dam et al 2004;2006), bagasse (Mobarak et al 1982), oil palm (Hashim et al 2012;Baskaran et al 2015), soybean straw (Song et al 2020) and bamboo (Shao et al 2009) etc. Recently, a review work on binderless fibreboards from agricultural residues was published summarizing the related studies (Nasir et al 2019).…”

Evaluation of cattail (Typha spp.) for manufacturing composite panels

“…Particleboards with 100% wheat exhibited lowest MOE (3.45 MPa) and this can be attributed to weak bonding between wheat straw particles due to presence of cuticular waxy layer. The negative effect of inorganic silica in wheat straw has been reported in a previous study (Mo et al, 2003;Zhao et al, 2014). Effective particle conformation between the particles of mixed fiber blends helped to reduce the voids, which helped the particleboard matrices to efficiently transfer stresses leading to higher MOE values.…”

Preparation of Wheat Straw Hot-Pressed Board through Coupled Dilute Acid Pretreatment and Surface Modification

“…The remarkable difference in tensile strength observed between glutaraldehyde-modified samples and the other two groups can be primarily attributed to the highly crosslinked network formed by the etherification reaction between glutaraldehyde and dilute acid-pretreated wheat straw. Compared to the mechanical strength of straw boards prepared by other methods without adhesive [22,[26][27][28][29], there remains a discernible gap in the mechanical properties of wheat straw boards prepared through the combined dilute acid pretreatment and surface modification. Nevertheless, the present study shows that the integration of these two processes can significantly improve the mechanical strength of wheat straw boards without the need for adhesives.…”