La Dunn

Study of the interaction between poly(ethylene oxide) and phenol-formaldehyde resin

Abstract Interactions between poly(ethylene oxide) and phenol—formaldehyde resin play important roles in the mechanism by which the two polymers improve fibre retention in the papermaking process. These were investigated at the concentration level and shear conditions found in this process. The results indicate that the complex formed varies with pH and ionic strength over a very narrow range of conditions, and that the self association of the resin plays an important part in the quantity of resin in the complex. Because the amount of resin interacting with the polyethylene oxide appears to be related to the molecular weight, and hence chain length, of the two polymers, cooperative binding of the polymers seems to be involved. A minimum size of the network was found to be necessary for the polymers to improve fibre retention.

Evaluation of Various Phenolformaldehyde Resins in the Phenolformaldehyde Resin—Polyethyleneoxide Dual Retention Aid System

Abstract Retention performance of the polyethylene oxide (PEO)-phenolformaldehyde resin (PFR) retention aid system is affected by the chemical structure and the molecular weight distribution of PFR. 1NMR and high performance liquid chromatography have been used to characterise various resole and novolak-based resins. Of the resins examined, those with the highest molecular weight gave the greatest retention improvement. The type of substitution around the aromatic ring of the resin appears to affect the interaction with PEO and the size and structure of the network formed when PFR and PEO are mixed together.

Adsorption studies of phenolformaldehyde resin onto cellulose fibres

Abstract Adsorption of phenolformaldehyde resin (PFR) onto microcrystalline cellulose was investigated as a function of pH. ionic strength, temperature and shear. The effect of adsorption was also studied by measuring the electrophoretic mobility of the cellulose particles. Adsorption was found to occur above a critical ionic strength. Suppression of the electrical double layer and reduced solubility of PFR appear to be necessary to promote adsorption. Increasing the intensity and duration of shear was found to increase the amount of PFR adsorbed. In the presence of high molecular weight poly(ethylene oxide) (PEO), complex formation between PEO and PFR also competes with the interaction between PFR and the cellulose particles. The mobility data indicate that the PFR directly affects the cellulose surface rather than the PEO.

Bleaching of Eucalypt Pulps Studied by Carbon-13 N.M.R. Spectroscopy

Abstract Cross polarization, magic-angle spinning, interrupted decoupling and paramagnetic doping techniques have been combined to provide the sensitivity needed for detection of chemical functional groups involved in pulp bleaching reactions. Cold soda pulp and stone groundwood pulp were bleached by calcium hypochlorite and hydrogen peroxide respectively. These treatments had little effect on ketonic structures and no effect on etherified aryl units, but hypochlorite degraded most lignin units not linked in beta-0–4 ethers. This work provides direct confirmation of published predictions based on bleaching of model compounds in solution.