Chitosan was precipitated onto wood pulp, glass and polypropylene fibers suitable for papermaking. The coating which formed on the fibers was characterized by photomicrography after the formation of colored derivatives, and by scanning electron microscopy. The most uniform and adherent coatings were formed on the wood pulp fibers and the least were formed on the polypropylene fibers. Paper handsheets were readily formed from the chitosan-coated wood pulp and glass fibers, but not from the chitosan-coated polypropylene fibers.

Paper and paper composites are utilized in applications where they are subjected to multiaxial stress states and changing environmental conditions. Such materials exhibit nonlinear anisotropic material behavior which is time dependent and affected adversely by slight changes in moisture content and temperature. At present, lack of adequate theoretical models often hampers the design and development of structurally optimized paper products. Therefore, it has been common practice in the pulp and paper industry to use trial and error, and empirical approaches. Accurate continuum models for the mechanical behavior of paper and paper composites are needed to guide the paper product design process.

In this work, a limited review of the existing methods for modeling the mechanical response of paper and paper composites is given. At first, a brief overview of the goals of current modeling techniques based on hydrogen bond, fiber network, and continuum approaches is presented. The governing equations and capabilities of current continuum models are then discussed in greater detail. Theories which include linear elastic (generalized Hooke's Law), nonlinear elastic (hyperelastic), linear viscoelastic, nonlinear viscoelastic, and inelastic constitutive relations are addressed. Finally, applications of existing continuum theories to the analysis of paper materials in structural configurations are presented. After these discussions, the limitations of the available continuum models are assessed and future research needs are suggested.

C.A. Hogart defined paper as “a random bonded fibrous network carrying filler material“. A few thoughts related to this definition and pertaining to paper composites are presented.

A typical papermaking furnish consists of a blend of cellulosic fibers and fines, inorganic fillers and additives. Composition varies according to end use requirements. The fiber network secures desired mechanical and strength properties, fillers contribute to esthetics and good optics. Filler retention is improved by using retention aids. Strength-loss due to filler, use is compensated for, by applying strength additives.

Additives applied at the wet end interact with furnish components. The surface charge, accessible surface area and composition play a role in the interactions. Some typical interactions, involving cationic starch and polyacrylamide, are discussed.

Studies are presented showing that formation of a sheet of paper from a heterogeneous mix of cellulose fibers and water at the forming section of a paper machine is a three-part process.

The studies were carried out using the Weyerhaeuser-developed G/W Drainage/Retention System of following the forming portion of the papermaking process and is a summary of work carried out over a five-year period of time.

Commonly referred to as PAC, a series of polyhydroxide chlorides of aluminum with the general formula Aln(OH)mCl3n−m are being increasingly used as rosin size bonding agents, drainage aids and retention aids in papermaking.

The manufacturing route chosen, the process kinetics and degree of neutralization affect the product produced and its reactions in the paper-making system. Production methods and procedures for quantifying the products produced are described.

Dispersed rosin size and PAC can be applied to a papermaking system operating at pH 6 to 7.3.

Sizing specifications are met and paper with non-slip characteristics, good machine glaze surface and printability is produced.

A pigmented paper coating is a composite material made of pigment, polymeric binder and microvoids. Its structure is designed to meet a difficult balance of optical, mechanical and fluid transport properties. The coating must be opaque and bright. It should withstand in-plane and out-of-plane stresses during calendering, printing, and converting operations. It should allow controlled movement of liquids and fluids during high speed printing and glueing.

The structure of paper coatings is examined and relationships between surface and bulk structural parameters and end-use properties are discussed. Namely, it is shown how pigment size and size distribution, its shape and orientation, the colloidal interactions between pigment and binder in the suspension all affect the final structure and properties. Finally, the profound influence of the porous network on the optical, mechanical and printing properties is emphasized.

The properties of coatings have been studied on a theoretical level using model systems of spherical polymeric pigments applied to a mylar substrate. Using binderless coatings, the expected void filling, gloss and light scattering relationships to particle size and polydispersity were observed. The addition of binders to the coatings yields results which depart from those expected and observed without binders. These results have led to two seemingly opposed views that the binder either coats the pigment and causes expansion of the structure or fills the voids without greatly effecting the pigment structure. Pigment blends were selected which were expected to show a difference between the two conflicting theories, and starch and latex binders added. The data obtained failed to favor one theory over the other, indicating that both are probably operative. Greater decreases in gloss were observed with the polymeric pigments, probably due to an undesirable interaction between the pigments and binders causing agglomeration of the coating materials and severe disruption of the coated surface. The data obtained is reviewed in light of the “real world” behavior of paper coatings to examine reasons why the theoretical contributions of pigments and binders are not often observed.

Novel composite materials have been fabricated from fibrous precursors using paper making procedures. Small metal fibers (2 μm in diameter) and carbon fiber bundles (20 μm in diameter) were combined with cellulose (as the binding agent) into an interwoven paper preform. The composite paper preform was then sintered at high temperatures in a controlled atmosphere, subsequently removing the cellulose and forming a sinter-bonded composite structure. The sinter bonding of the metal locked the metal fibers and provided high mechanical flexibility and structural integrity to the resulting composite structure. The composite structures were characterized using scanning electron microscopy, electrochemical and kinetic measurements. The optimization of these structures for high energy density applications was demonstrated through these measurements.

This article describes a print quality evaluation of laboratory designed ink jet papers prepared on a dynamic former. A comparison with various plain and coated papers serves to illustrate the potential opportunity for papermakers to exploit novel types of paper structures in the future. The article will also briefly focus on some of the fundamental issues and key paper properties which perturb print quality and govern the capillary absorption of aqueous inks.

Magnetic paper handsheets with pigment loadings in the order of 10–30%, depending on the experimental conditions, have been made using the established “lumen-loading” technology. These sheets have bulk magnetic properties comparable with the computer floppy-disk products. In order to minimize the particle size of pigments and thereby explore a new level of optical and magnetic properties, in situ synthesis of pigment particles is a second approach. This chemistry starts with a carboxymethylcellulose substrate with ion-exchange properties for Fe(ll). The substrates, before and after oxidation reactions to produce ferrite particles, are characterized by: conductimetric titration, x-ray diffraction, thermogravimetric analysis, and magnetization determination. Electron microscopy and diffraction provide insight on the ferrite morphologicals. These specialty fibers allow exploration of new concepts in papermaking, information storage, security printing and paper handling.

The trend toward alkaline papermaking has accelerated over the past four years due to the availability of inexpensive, high quality precipitated calcium carbonate. This movement has been largely brought about through on-site production of precipitated calcium carbonate (PCC). Over ten facilities exist in North America providing the host mills with custom-made PCC products to provide specific properties for the paper grades being manufactured.

Laboratory studies were recently conducted to investigate the performance of paper-grade PCC fillers in fine quality printing papers. This investigation focused on the effect of changes in PCC particle size, size distribution, surface area, and morphology on paper properties. The PCC fillers were also compared to other filler materials such as ground limestone and kaolin.

In general, the results show that sheet properties are greatly influenced by the size and shape of the PCC product used. The data reveal strong correlations between average particle size and/or surface area, and sheet properties such as opacity, porosity, tensile strength, bulk, and sizing within certain filler morphologies.

Previous work has shown that certain cationic solutes can adsorb “specifically” at the solid-solution interface [1,2]. To do this, a counterion must have a high enough “specific adsorption potential”. This is difficult to predict theoretically, and can best be studied is by electrokinetic titration.

In this work, we have performed electrokinetic titrations of a diverse group of pigmentary materials such as clays, TiO2 and silicates. Using this information, we have cationized TiO2 and measured the effect on its retention in paper. A Dynamic Handsheet Mold was used for this work. Kaolin clay was also cationized and used to prepare cationic paper coatings.

Sophisticated surface science techniques long familiar to materials researchers are now being used routinely to characterize the colloids found in papermaking systems. Ion Scattering Spectroscopy (ISS) is used to obtain the surface elemental composition of inorganic filler pigments. Laser light scattering is applied to the determination of particle size and particle charge distribution by way of the methods of Photon Correlation Spectroscopy (PCS) and Doppler Electrophoretic Light Scattering (DELS). The heats and races of interaction of hydrophilic colloids (water soluble polyelectrolytes) with hydrophobic colloids are determined by batch titration microcalorimetry.