Effects of addition ammonia modified urea-melamine -formaldehyde resin on the adhesions and formaldehyde emission in plywood

摘要

This study was carried out to investigated the effect of addition ammonia which concentration is 20 percent modified urea-melamine-formaldehyde resin on the formaldehyde emission and internal bonding strength,when hotpress temperature,time and pressure for every plywood was coincide. To determine and compare the effect of ammonia content 0, 2.5, 5 percent by weight of formaldehyde were used. Wheat flour,15% by weight of adhesive,was added as material to increase the quantity. To determine the level of formaldehyde emission, we used the desiccator method. The formaldehyde emissions from poplar multi-plywoods were significantly decreased with increased additions of ammonia, at a ammonia ratio of only 2.5%, the formaldehyde emission level of the un-coated samples which is seven-ply plywood can meet the F grade, and also the samples with 2.5% ammonia modified resin hot-pressed showed good bonding strength.