||January 1, 2006
This is a study of carpet latex adhesive rheology to qualify penetration into backing webs during frothed carpet compounds applications. A rheological test depicting 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. A fluid dynamic model that predicts the shear and pressure distributions in the compound metering nip based on process parameters and rheological results was developed. We tested frothed compound formulations that are empirically known to be “penetrating” and “non-penetrating” based on the choice of soap. Compared to formulations that do not penetrate into carpet backings, penetrating formulations had large froth bubbles, relatively low shear viscosity and showed increasing foam breakdown due to shear. 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.