The surface chemistry of water-reducible polymer solutions/dispersions 1. Surface tension behavior

Abstract

Both static tension and dynamic surface tension of water-reducible (W/R) polymer solutions were carefully examined. It is shown that the cosolvent and its concentration are controlling factors in surface tension behavior for most concentration regions of W/R polymer solutions. This is true for both static and dynamic surface tensions. The polymer and its concentration have a much smaller effect on static surface tension than does the cosolvent. Much of the dynamic surface tension correlates with the bulk shear viscosity of W/R polymer solutions. The examination of cosolvent /water mixtures shows a critical solution concentration (CSC) for most cosolvents, analogous to the critical micelle concentration (CMC) in surfactant solutions. Both CSC and CMC originate from the same structural characteristics, i.e. molecules having a hydrophilic head and hydrophobic tail. Typically cosolvents have a less hydrophobic nature so values of CSC are higher than those typical of CMC for surfactants. This CSC plays a unique role in the surface tension of W/R polymer solutions. Above the CSC, constant surface tension is observed, while below the CSC a rapid increase in surface tension with decrease of cosolvent concentration occurs.