P. Labosky et al., EFFECT OF STEAM PRESSURE REFINING AND RESIN LEVELS ON THE PROPERTIES OF UF-BONDED RED MAPLE MDF, Forest products journal, 43(11-12), 1993, pp. 82-88
A study was undertaken to determine the influence of steam-pressure-re
fining levels on red maple (Acer rubrum L.) wood chips fabricated into
medium density fiberboard (MDF) test boards using four urea-formaldeh
yde resin levels. Red maple chips were fiberized using a pressurized,
double-disk refiner operating at six refining pressures (50, 60, 70, 8
0, 90, and 100 psi). MDF test boards were produced using the six group
s of refined fibers at four urea-formaldehyde resin contents. Static b
ending (MOE and MOR), internal bond (IB), water absorption, and thickn
ess swell properties were measured. An increase in refining pressure d
id not significantly affect MDF strength or dimensional stability prop
erties. In contrast, the resin content of the boards had a significant
effect on all board properties. An increase in resin content from 6 t
o 12 percent resulted in a 174 percent increase in internal bond stren
gth, a 68 percent increase in the modulus of rupture, and a 40 percent
increase in the modulus of elasticity, whereas thickness swell and wa
ter absorption properties decreased by 113 and 60 percent, respectivel
y. Preliminary data indicate that the most significant factor, other t
han resin content, influencing both fiber and board properties was the
wood chip moisture content during refining. Nearly all fiber and MDF
properties were affected by the addition of moisture to the wood chip
prior to refining. Further investigations concentrating on wood chip m
oisture content during refining and refiner plate design should be con
ducted in order to more clearly understand the relationship between re
finer variables and red maple MDF board properties.