Low-cost Fast-curing The Development Of Environmentally Friendly Urea-formaldehyde Resin

The GB/T18580-2001 standard was put in practice in July 1, 2002, which bring a serious test for the plywood industry. Wood-adhesive technique is frail in some aspects in our country then some countries, such as high formaldehyde emission, short storage life, high cost, low solidified speed. It is no-good to the development of the plywood industry.In order to solve the above deficiency, the main contents of this study are as follows: analysis low mol-ratio U-F resin into twokinds of mol-ratio U-F resin, then confect, optimize the technique , think of ways to make formaldehyde and urea react in adequate. To increase the U-F resin's curing speed and decrease the free formaldehyde, adopting two-times polymerize. Using such method, the cost will decrease 30 percent and 20 percent comparing to add melamine and dehydrate.During the experiment, we design math model and arrange experimental scheme with regressive analysis method. According to experimental results, we can achieved :Combine with the plywood produce technique, we changed the proportion of different resins to make the optimize formulus, the ideal formulus is: (F/U=1.3):(F/U=1.0)=2:3. And the hot-press technology of plywood is : P=9kgf/cm2 T=110℃ t=3min+lmin.Lower Urea/formaldehyde molar ratio does ensure lower free formaldehyde and higher solids content, but the harderning time is worse; and these giving low formaldehyde and bad adhesion.Increase the number of additions of urea, the resin has a lower free formaldehyde, longer harderning time. And the plywood has a lower formaldehyde emission also, but 5-urea-additions is the most.And increase the number of additions of formaldehyde, the free formaldehyde is decreased, the rate of curing time is short. And at the same time the emission of plywood is decreased . but the effect on bonded strength was not obvious.