CATIONIC LATEX INTERACTION WITH PULP FIBERS .2. MODIFICATION OF SHEET PROPERTIES BY STYRENE-BUTADIENE LATEX WITH QUATERNIZED AMINO-GROUPS

Unbeaten kraft fibers covered with experimental cationic latexes were formed into sheets in which direct fiber‐fiber bonds are replaced by polymeric bonds. The effect on sheet properties—breaking length, elongation at break, folding endurance, opacity, and light scattering—was evaluated as a function of latex composition. The composition was altered by either the ratios of styrene to butadiene in the polymer or by mixing soft film‐forming and hard nonfilming latex. It is shown that, regardless of latex composition and mechanical properties of the polymeric film, all the latexes can modify the sheet properties to a similar extent, providing that the sheets are heated above the polymer's glass transition temperature. An improvement of tensile strength is accompanied by increased elongation. As a probable mechanism of reinforcement, it is suggested that the polymer acts as a filler of the fiber's surface irregularities, thus providing a larger contact area between fibers and an improved stress transfer between them. Copyright © 1979 John Wiley & Sons, Inc.