Nanoclay plating of cellulosic fiber surfaces

Abstract

A basic problem in making cellulose-reinforced composites is achieving a dispersion of cellulosic fibers in an often olephinic polymer matrix. Drying cellulosic fibers results in the formation of fiber flocs/nodules because of their strong interfiber bonding, and this makes the hydrophilic cellulosic fibers difficult to disperse in a hydrophobic matrix material. One common approach to alleviate floc formation is to adsorb cationic surfactant onto anionically charged cellulose, which reduces the interfiber bonding, decreases floc formation and gives better compatibility with the matrix. In this report, a different approach is taken, namely to adsorb nanoclays onto the cellulosic fibers, and thereby reduce the natural hydrogen-bonding affinity between fibers. In a second report, the same technology will be shown to be advantageous to decrease floc formation in oleophinic composites reinforced with cellulosic fibers. This article summarizes experiments aimed at optimizing the chemistry of deposition of montmorillonite clay onto fiber surfaces. The aim was to optimize the chemical conditions for the heterodeposition of the anionic clay onto cationically charged fluff pulp. The experiments were designed to provide a theoretical framework for the deposition of the nanoclay onto the pulp fibers. High Mw p-DADMAC and an exfoliated clay (achieved by passing the clay through a homogenizer) were used. As expected, a certain degree of charge overcompensation by adding an electrolyte was necessary to bring about deposition. The adsorbed amount of clay could be calculated from the charge balance between the overcompensated charge and the net clay charge, constituting the theoretical framework for nanoclay heterodeposition. As expected, montmorillonite clay greatly destroyed the joint strength between fibers (determined by evaluating the strength of paper made from treated fibers). The surface coverage (determined by ESCA) was shown to be a linear function of the attached amount of clay, and ∼3% clay was required to fully cover the fiber surfaces. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008