Optimising the process for production of high performance bagasse-based composites from rice bran-UF adhesive system

The purpose of this paper is to prepare high-performance agro-based composites from the non-toxic rice bran-urea-formaldehyde (RB-UF) adhesive system. Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches. The utilisation of such system with the available used local agro-based wood products (sugar-cane bagasse, SCB) adds economic value and helps reducing the environmental impact of commercial urea-formaldehyde (UF) adhesive, and most importantly, provides a potentially inexpensive alternative to the existing commercial artificial wood-panel mills.

Optimising the process for incorporating the RB in UF, as wood adhesive for binding the bagasse fibres, was carried out, by partially replacing commercial UF by denaturalised RB in slurry (wet) and dry form or through synthesis of UF. The denaturalisation of RB was carried out at different pHs (10-11) and at temperature 60°C for two hours. While incorporating the RB during synthesis of UF, it was carried out according to the method reported elsewhere. The formulation of adhesive components, pH value of the denaturalisation stage and the process of incorporating the RB were optimised. Assessment of the role of RB adhesive was specified from its free-formaldehyde (HCHO) content, as well as the properties (mechanical and physical properties) of the produced composites of bagasse particle board type, in comparison with the environmental impact of commercial thermosetting resin (UF).

The promising adhesive system exhibits improvement in the environmental performance (as E1 type) over a commercially UF adhesive (as E2 type), besides providing boards fulfill the requirements of grade H-3 (according to ANSI A208.1 (NPA1993). This adhesive system was resulted from replacing 30 per cent of UF by denalturalised RB (at pH 10) in slurry form. Where, its reduction in free-HCHO reached 53 per cent, as well as modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB) and TS of the produced boards were approximately 24.2 N/mm2, approximately 3753 N/mm2, approximately 0.84 N/mm2 and approximately 11.4 per cent, respectively.

The eco-adhesive with relatively high percentage of low-cost commercial UF (70 per cent) and 30 per cent RB, as oil production by-product, in slurry form provides good board strength and is environmentally friendly compared to SCB-based composite properties, with that produced from commercial UF. The mechanical (MOR, MOE and IB) and water-resistance properties of the produced composite comply with the standard values.

The approach provided low HCHO-free UF adhesive with good comparative board strength and water resistance and reasonable working life. Replacing 30 per cent of UF by RB in slurry form and denaturalised at pH 10 is considered a promising inexpensive alternate adhesive (as E1) in the wood industry based on SCB wastes.

Incorporating the RB by-product of oil production to commercial UF will be beneficial for saving the health of wood co-workers and motivating the wood mill to export its wood products.

It provided a potentially simple way to improve both the utilisation of commercial UF and SCB as industrial substrates for particle-board production. This will benefit farmers, local wood mills in Upper Egypt, significantly. Meanwhile, incorporating low percentage of RB, as oil-mill by-products, is promising to partly replace UF resin in the wood industry, minimising formaldehyde emission or toxic gasses during board formation.