Comparative Study of Bond Strength of Formaldehyde and Soya based Adhesive in Wood Fibre Plywood

Abstract

Plywoods, particleboards and medium density fibreboards are currently used in the construction of houses, furniture, partitions, etc. These usually incorporate some form of formaldehyde as part of the adhesive system. Formaldehyde-based adhesives are known to be harmful as formaldehyde emissions during manufacture and after installation are known to be carcinogenic and have other undesirable health effects. This and other environmental concerns have in the recent past led to an interest in ‘green’ adhesives from biological sources that are sustainable and environmentally friendly. Green adhesives are one of the green building practices, which aim to construct buildings that are environmentally responsible, economically viable and healthy places to live and work. The objective of this investigation was to explore environmentally friendly biobased adhesives for plywood manufacturing. This study proposes a natural biobased adhesive that was developed using soya flour, phenol, Plaster of Paris and an agro-based powder as the binder. A comparison of modulus of rupture of the plywood developed using the proposed soya-based adhesive with popular plywoods, including the traditional urea-formaldehyde based plywood has also been undertaken. The three-point bend test (to identify the modulus of rupture) was conducted for all the plywoods compressed at a fixed pressure. It was observed that the soya-based adhesive imparts greater strength to the plywood than the formaldehyde-based adhesive. It is also desirable for wood and wood-based composites to have fire-retarding and microbial-resistant properties by utilising non- toxic additives and treatments. Traditional methods of achieving these objectives have been harmful; for example, timber has been treated with arsenic-based chemicals to make it resistant to microbes. This paper also presents future research directions to render wood-based composites free of toxic additives as well as being sustainable and environmentally friendly.