The influence of gas diffusion mechanisms on foam stability for foam forming of paper products

Abstract

Foam forming is an innovative process for papermaking that yields various paper products with excellent formability and porosity. The stability of the foam is a critical factor in foam forming technology. The effects of different surfactants and gases (N2 and CO2) on the ability of the foams to coalesce and the stability of the foams were studied. The properties of the liquid film were investigated via high-speed camera observation and infrared spectrum. The CO2 foam was less stable than the N2 foam under the same conditions, especially for the polyvinyl alcohol surfactant. The infrared spectra and high-speed camera observation showed that the main factor that resulted in CO2 foam instability was the bubble coalescence caused via the gas diffusion in the foam column, although the process of liquid film thinning was performed simultaneously. The greater the liquid film permeability coefficient of the foam, the easier the gas was able to spread throughout the liquid film. Foam forming technology will likely be employed in many potential pulp and papermaking mill processes.