Effect of Degree of Saponification and Molecular Weights of PVA on Properties of Low Density Foam-formed Sheets

The effects of saponification degree and molecular weight of polyvinyl alcohol (PVA) on foaming ability, foam stability, and strength of foam-formed sheets were investigated to evaluate the possibility of PVA for strength improvement of low-density foam-formed sheets. When used in combination with sodium dodecyl sulfate (SDS), the degree of saponification and molecular weight of PVA had no significant effect on the foaming ability of the fiber foam. However, the stability of the fiber foam was observed to improve with lower saponification degree and higher molecular weight of PVA above a certain level. Increasing the molecular weight and the added amount of PVA increased the bulk of the foam-formed sheet while decreasing the tensile strength. This is due to the fact that the added PVA contributed to the bulk improvement more by improving the stability of the fiber foam than by improving the interfiber bonding. In order to improve the strength of foam-formed sheets while maintaining low density, other methods need to be explored to increase the bond strength at the fiber-fiber interface.