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Dry-formed networks of cellulose fibers, produced with a laboratory device, have been impregnated with aqueous solutions of poly(vinyl alcohol) or solutions of poly(vinyl acetate) in acetone. In both cases, the strength and stiffness of the networks increase several times compared with the unmodified structure. When aqueous solutions are used, it appears that a minimum amount of poly(vinyl alcohol) is required (ca. 2 wt %) to increase the strength appreciably, but when poly(vinyl acetate) dissolved in acetone is used, as a binder, the strength improves even at the lowest level of polymer addition. For the systems studied here, the elongation at rupture increased with increasing polymer concentration. In most cases, the amount of polymer in the network structure was less than 10 wt %. Some results from impregnations using other polymeric systems, e.g., latices, are also reported.

In dry-formed polymer-bonded networks of cellulose fibers and in other types of nonwovens, the fiber-polymer joint is considered to be the primary factor determining the ultimate properties of the network structure. In an attempt to develop a model describing the joint failure, the well-known fiber pullout test has been applied to a system consisting of regenerated cellulose fibers and three different polymer matrices: a styrene–acrylate copolymer, poly(vinyl alcohol), and high density polyethylene. For each system, the interfacial bond strength was evaluated. The results are, to some extent, discussed in relation to the mechanical behavior of dry-formed networks bonded with similar polymeric materials. It is suggested that both the interfacial properties and the cohesive strength of the polymer binder are of importance for the mechanical strength of the bonded network.