Abstract:
Dry strength is an inherent structural property of
a paper sheet. It is due primarily to the development
of fiber-to-fiber bonds. Polyamines, especially
polyallylamine·HC1 (PAA), were found to be suitable
mordants for rosin sizing. However, their effectiveness
as dry strength agents has not been studied. In this
study polyallylamine·HC1 was found to be an effective
dry strength agent. With unbleached kraft pulp, 0.5%
PAA on mass of oven dry pulp was sufficient to increase
the dry strength of handsheets, while bleached kraft
pulp required more PAA based on the mass of oven dry
pulp. Different strength properties were measured and
it was found that the largest increase was in the folding endurance of the handsheets. The strength
properties were highly dependent on the drying
conditions of the handsheets.
In this paper dry strength development is
discussed based on the interaction between protonated
(cationic) PAA and the cellulosic fibers and between
the interaction of the cationic amine and the aromatic
[pi]-bonding of lignin. PAA was effective as a dry
strength agent and the bursting strength, folding
endurance and the tensile strength increased for
handsheets made from different types of pulps using
polyallylamine·HC1. PAA is a promising material that may
offer superior performance in some specialized
applications.
