Resin Distribution in Layered Particleboard

Resin distribution in multi-layer and three-layer particleboards was studied by varying the resin levels of each layer while maintaining a constant total resin content in the board of 6 percent (O. D. basis). Optimum resin distribution on a weight basis for multi-layer boards appeared to range from approximately 8 percent for face particles to about 5 percent for core particles. Three-layer boards, on the other hand, showed superior properties with 6 percent resin in both face and core layers. On a surface-area basis in multi-layer boards, coarse particles with a resin spread 2 to 3 times greater than on the finer particles provided the optimum situation for bonding. A complex relationship between layer specific gravity and resin spread was noted here. Fine particles with a relatively high surface-area-per-unit-weight, located in high density surface layers, required much less resin than the coarser particles with a much lower surface-area-per-unit weight comprising the low density core layer. Thus, surfaces with high layer densities made more efficient use of the resin, which actually allowed for a substantial reduction in resin while maintaining high modulus of rupture and internal bond properties in the board. Consequently, an even spread of resin on a surface area basis in particleboard with high density surface layers composed of fine particles and low density cores consisting of coarser particles, was not the optimum blending condition.

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