Latex Carpet Compound Rheology

Abstract

This is a study of three-phase foam rheology to qualify penetration in to backing webs during frothed carpet compounds applications. Transient viscosity as a function of shear rate under a short time period is proposed to characterize flow of these compounds in response to a rapidly changing shear field during their application. We developed a fluid dynamic model that predicts the shear and pressure distributions in the compound during its processing in a metering nip based on process parameters and rheological results. We tested frothed compound formulations that are empirically known to be “penetrating” and “non-penetrating” based on the choice of soap (frothing surfactant). Formulated at the same froth density, penetrating to carpet backing compounds had large froth bubbles, relatively low transient shear viscosity and showed increasing foam breakdown due to shear when compared to non-penetrating compounds. Such frothed compounds readily collapse under shear and have relatively low dynamic stability, so the transition from a three-phased (air/aqueous/solid) to a two-phased (water/solid) system occurs much easier and faster during application. The model predicts the shear rate development and a small difference in the pressure distributions in the applicator nip between these formulations, but reduction in drainage for the non-penetrating formulation.

Keywords

• foam rheology
• bubble formation
• shear viscosity
• carpet compounding