Reinforced Plastics as Protective Coatings for Wood

A study was instituted to determine if encapsulation of balsa wood with fiber glass reinforced plastic (polyester) would promote or prevent decay. In 1957 over 75 percent of all “glass” boats contained wood embedded within the reinforced laminate. Theories tested were: A: The reinforced plastic coating prevents decay under any type of moisture condition, because decay fungi are killed at the time the laminate is applied and are excluded thereafter. B. The plastic prevents decay only if water does not penetrate the laminate, because it is virtually impossible to eliminate all the fungi within the wood core. C. The coating prevents decay regardless of the presence of fungi because free access to air is halted and the normal metabolism of the fungi is prevented. D. The reinforced plastic coating promotes decay because wood must “breathe” and prevention of this induces “dry rot.” E. Decay is promoted because water condensate can buildup in the core because the coating is not a vapor barrier. The test program included exposing encased blocks to fungal cultures, isolation to determine presence of decay fungi in the test block, and determining the effect of the various ingredients of common polyesters and epoxy resin formulations on the fungal cultures. Conclusions are that Theory A is correct, Theory B is not substantiated, Theory C is neither rejected nor accepted, Theories D and E are rejected.

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