Particleboard Strength as Affected By Unequal Resin Distribution on Different Particle Fractions

Varying resin distributions within various particle size classifications (screen fractions) of particleboard furnish affected IB, MOR, and MOE. Two studies were made. First, a commercial particleboard furnish was screened into four fractions, and boards were made at three densities so that each board had a different percentage of unblended particles from a different screen fraction. Second, the two coarsest and the two finest fractions were combined. Boards were made at the same three densities so that each board contained a controlled percentage of unblended particles from one of the fractions. When the entire fines fraction (-20 mesh Sweco) was unblended, strength properties were lower than when the entire coarse fraction ( mesh Sweco) was unblended. The large relative surface area of the unblended fines (87 percent of the total surface area of the furnish) appear to have caused this decrease. Plotting average for each ratio of unblended particles showed that the laboratory blender could meet present commercial standard for IB if 50 percent of the board’s furnish was unblended. Optimizing resin coverage and spread rate.within each fraction seems the best way to increase resin efficiency in commercial particleboard blenders. This could probably be accomplished by applying resin at a relatively even spread rate, based on surface area, on the various sizes of particles.

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