Enhancing environmental performance of formaldehyde‐based adhesive in lignocellulosic composites – Part II

Abstract

Purpose -To investigate a new approach for the prevention of lignocellulosic composites based on agro-fibres (e.g. sugar-cane bagasse) from the emission of toxic formaldehyde. Design/methodology/approach -Five organic polymer containing nitrogen-urea formaldehyde (UF) adhesive systems were used as bonding agents for bagasse fibres. The environmental performance of the lignocellulosic composites prepared were evaluated in terms of the effect of the organic polymers on the percentage of free formaldehyde in the adhesive system and the adhesion properties (static bending and water resistance properties) of the composite produced, in comparison with that prepared from un-modified UF. The nitrogen content of the polymer and the amount of organic polymers incorporated in the adhesive system were optimised using the 3D response surface methodology and the multi-linear regression technique. Findings -All investigated organic polymers (crude PAM-g-starch, PAM-g-starch, PAM, CE-starch and Cm-starch) were found to enhance the performance of the UF-adhesive for producing environmentally friendly bagasse-composite, whereas the reduction of free-HCHO in UF-adhesive systems ranges from 26 to 100 percent. The performance of the composite produced exceeded the ANSI requirements for Grade H-3 particle-board. Research limitations/implications -Despite the success in improving the performance (mechanical properties and reduction of free-formaldehyde) of the UF-adhesive and agro-composites, the polymers needed to be incorporated at a high percentage (12-20 percent) resulting in reduced water resistance of the product. Further investigation is needed to resolve this problem. Practical implications -The approach developed provided a simple and practical solution to enhancing the performance of waste agro-fibres and commercial amino adhesive in the production of high performance lignocellulosic composite. Originality/value -The organic polymers UF adhesive systems are novel bonding agents for agro-fibres and could be used in timber mills for production of particle-board and medium density fibre-board.

Wood production, wood technology, and biotechnological impacts

“…However, there are source-dependent differences and these will influence the properties of the starch as adhesive , Eriksson et al 2005. In spite of this, a common problem with starch-based adhesives is a reduced water-resistance of the products (Basta et al 2005, Dix 2006see below).…”

“…Starch (native or modified) with conventional phenol-, melamine-or ureaformaldehyde resins, bacterial EPS with phenol-formaldehyde (PF) resin and mixed composites of starch and tannin (see below) can even provide better board properties since the positive features of the different co-adhesives are combined (Conner et al 1989, Dix 1987, Dix & Marutzky 1988, Johnson & Kamke 1994, Imam et al 1999, Turunen et al 2003, Basta et al 2005, Weimer et al 2005. Combinations of native, unmodified starch with UF resins are however unsuitable (Plath 1972).…”

“…Furthermore, it is used as adhesive in manufacturing of corrugated boards (Borchers et al 1993, Höpke 2002. Starch is also added as an extender to various types of conventional adhesives in order to enhance their environmental performance by reducing the absolute usage of synthetic resins and, in consequence, thereby also the emissions of toxic formaldehyde as well as the production costs (Basta et al 2005, Müller 2005see below). Moreover, starch may act as a scavenger for free formaldehyde (Basta et al 2006).…”

Preformed Amide-containing biopolymer for Improving the Environmental Performance of Synthesized Urea–formaldehyde in Agro-fiber Composites

“…Maize starch from Miser Co. and glucose were modified by acrylamide (AM) using previously developed method [13]. Prehydrolysis of the starch at different concentrations of hydrochloric acid, at different times and temperatures, and at differing AM-to-starch ratios provided a series of five starch derivatives [HSt (A), HSt(B) & HSt (C), HSt (D), HSt (E)].…”

“…Numerous studies have dealt with using formaldehyde-free adhesives, namely; thermosetting or cross-linked type of polymers, e.g., isocyanate binders and polyvinyl alcohol, or using natural products e.g., natural tannin and proteinaceous adhesives [7][8][9][10][11][12][13][14][15][16][17][18][19]. The isocyanates and phenol formaldehyde resins are reported to be good adhesive bonding agents for agricultural waste such as straw and rice husks [11].…”