Bonding of Agrofibers-based t]omposition Panels

Urea formaldehyde resins were formulated with vatiables of three reaction pHs (1.0, 4.8, and 8.0 5.0) and three catalysts (sodium hydroxide, sodium hydroxide/ammonium mix, and triethanolamine) . The resins were prepared by placing all formaldehyde and water in reaction kettle and pH was adjusted with sulfnric acid and sodium hydroxide, respectively. Urea was added in 1.5 equal parts at 1 minute intervals. The proportion of high molecular weight products in the rosin increased substantially as the reaction pH decreased. The formation of a high percentage of uron derivatives under strong acidic conditions indicated these resins differed considerable from conventional UF resins formulated in the past. Bagasse panels bonded with UF resins formulated with acidic pH resulted in higher IF3 than with those formulated with the conventional alkaline acidic pH system. Similar results were also shown with PMDIAJF bonded Bagasse panels. The apparently higher IB strength of PMDI/UF resin systems indicate that these resin systems would be expected to provide the greatest potential for further improvement in terms of IB/cost basis. It is noted that mixed catalyst systerfLof sodium hydroxide/ammonium and triethanohunine yielded a higher average IB, while sodium hydroxide catalyst resulted in a lower IB than commercial UF resin used as control. Since the cost of UF is substantially lower than that of PMDI, economic gains of PMDI/UF resin could be significant by using UF resin as the major component in the system.