Among the various floorings, we chose laminate flooring and
engineered flooring. Currently, these are extensively used in new
apartment interiors and in the remodeling market in Korea. Lami-nate flooring is composed of waterproof, high-density fiberboard
(HDF) as the core material, with overlay paper, deco paper and
valance paper. The wood fiber, for HDF, distributed from Dong-wha Enterprise was made from Korean pine (Pinus densiflora) with
a moisture content of 4%. Urea–melamine–formaldehyde (UMF)
resin was used to manufacture HDF. The molar ratios of the resin
was 0.95 (F/M + U). Before the HDF was manufactured, 3 parts (to
resin) of 25% ammonium chloride as a hardener and 13 parts of
44% wax solution for water-proofing were added. The wood fiber
distributed from Dongwha Enterprise was made from Korean pine
(P. densiflora) with a moisture content of 4%. The MDF was manufac-tured using the above adhesives, in order to have a specific gravity of
0.8. The mixture was then hot pressed, to form composite boards, at
a peak pressure of 40 kgf/cm
2
and a temperature of 180
◦
C. The main
pressing time was 4 min and the pressure was then released in two
steps of 1 min each. Overlay paper, deco paper and valance paper
were impregnated with melamine-papers pressed at about 200◦
C
and called low pressure melamine (LPM) as shown inFig. 1a. The
resin for impregnation is shown inTable 1. Finally, the edges of the
product are machined to produce a tongue and groove profile. In the
case of engineered flooring, 0.5 mm-thick fancy veneer of maple is
glued to a 7.2 mm-thick plywood sheet and pressed at about 160
◦
C.
A UV-curable coating is coated on this fancy veneer as shown in
Fig. 1b. The UV-curable urethane acrylate system consisted of three
main components; urethane diacrylate oligomers, reactive diluent
monomer and photoinitiator. The manufacturing step of laminate
flooring for this research was divided into two steps; HDF only and
HDF with LPMs. In the case of engineered flooring, the manufactur-ing steps were divided into three steps; plywood only, fancy veneer
bonded on plywood and UV coated on fancy veneer with plywood