Synergistic Effect of Alkali Metals on Fire Proofing Properties of Boric Acid-Containing Melamine-Formaldehyde Condensates

Abstract

The durable fire-retardants based on the colloidal solution of boric acid- and alkali metal containing melamine-formaldehyde condensates (H3BO3·AOH·MFAC) and 10 boron-containing inorganic compounds have been applied to Hinoki (Chamaecyparis obtusa Endl.) sliced veneer, Lauan (Shorea negrosensis Foxw.) plywood, and Sugi (Cryptomeria japonica D. Don.) shake. The condensates were prepared by use of boric acid, hydroxide of alkali metal and melamine-formaldehyde condensation products. These boric acid- and alkali metal-containing melamine-formaldehyde condensates given clear solution in both neutral and alkaline. The borates used were the same as those appeared in a paper of M.A. Kasem and H.R. Richard.5)The treatment of Hinoki sliced veneer was accomplished by soaking samples in an aqueous solution of these condensates and borates, drying at a room temperature and curing at 160°C for 30min. The treatment of Lauan plywood and Sugi shake were done by soaking in the aqueous solution of the fire-retardants and reducing the pressure by using a vacuum pump, drying at a room temperature for 1 month, and then curing at 160°C for 30min.The effects of alkali metal kind and of varying ratio of fire retardant components in treating solutions on the fire-proofing efficiencies of Hinoki sliced veneer, Lauan plywood, and Sugi shake were discussed. Boric acid-containing melamine-formaldehyde condensates combined with alkali metals imparted excellent fire-proofing resistance to wood and plywood. Satisfactory fire-proofing efficiencies can be obtained in Hinoki sliced veneer, Lauan plywood, and Sugi shake at resin content as low as 5-10%. The overall afterglow of the treated samples depended on the competition between the inhibiting effect of boron and the enhancing effect of alkali metals.