Effect of steam pressure refining and resin levels on the properties of UF-bonded red maple MDF
1993
Labosky, P. Jr | Yobp, R.D. | Janowiak, J.J. | Blankenhorn, P.R.
A study was undertaken to determine the influence of steam-pressure-refining levels on red maple (Acer rubrum L.) wood chips fabricated into medium density fiberboard (MDF) test boards using four urea-formaldehyde resin levels. Red maple chips were fiberized using a pressurized, double-disk refiner operating at six refining pressures (50,60.70,80.90, and 100 psi). MDF test boards were produced using the six groups of refined fibers at four urea-formaldehyde resin contents. Static bending (MOE) and (MOR), internal bond (IB), water absorption, and thickness swell properties were measured. An increase in refining pressure did not significantly affect MDF strength or dimensional stability properties. In contrast, the resin content of the boards had a significant effect on all board properties. An increase in resin content from 6 to 12 percent resulted in a 174 percent increase in internal bond strength, a 68 percent increase in the modulus of rupture, and a 40 percent increase in the modulus of elasticity, whereas thickness swell and water absorption properties decreased by 113 and 60 percent, respectively. Preliminary data indicate that the most significant factor, other than 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 moisture content during refining and refiner plate design should be conducted in order to more clearly understand the relationship between refiner variables and red maple MDF board properties.
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