4. Conc lusion
PVAc was added to reduce formaldehyde emission in
the adhesion between plywoods and fancy veneers by
replacing the formaldehyde system resin. The formaldehyde emission level was decreased with increased
additions of PVAc as replacement for MF resin. At a
PVAc replacement ratio of only 30%, the formaldehyde
emission level of the coated sample was under E1 grade.
The formaldehyde emission from these samples was only
caused by the presence of MF resin. With high MF resin
contents in this adhesive system(MF resin with PVAc)
was well cured, indicating that the bonding strength was
increased. In the case of PVAc only, the bonding
strength was much lower due to the already high
temperature of 120 1C.The adhesion layer was broken
by high temperature and pressure. The sample with 30%
PVAc added to MF resin (MF resin: PVAc ¼ 70:30)
showed good bonding strength compared with MF resin
only in all cases, with hot-press temperature, time,
pressure and boiling test. According to the results of
formaldehyde emission and bonding strength, the
adhesive systemwith an ‘MF resin: PVAc ratio of
¼ 70:30’ was the best formula for adhesion between
plywood and veneer. Although the bonding strength
was increased with increase in MF resin content in this
adhesion, the formaldehyde emission level was also
increased.