Finely ground scrap polyurethane foam (Mobius Powdered Urethane, or M-PU) is used commercially in the production of new slabstock. The ability to reformulate to maintain density, hardness, and other properties is key to
mechanical recycling. Here, we present results of recent flexible slabstock trials with powdered urethane, and relate
them using simple mathematical models for the density, hardness, SAG factor, and maximum block temperature.
The models can be used to add powdered urethane to new formulations, or to define practical limits for the use of
recycled powder in foams, or to estimate the cost savings achieved by using powdered urethane. Comfort factor (or SAG factor) is generally improved by the addition of powdered urethane. When foams are formulated to maintain density and 40% IFD, the increase in SAG factor is due to an increase in 65% IFD and a slight decrease in 25% IFD.
This work is focused on the prediction of four key quantities for conventional slabstock foams made with Mobius Powdered Urethane (M-PU): density, hardness, SAG factor, and maximum block temperature. These quantities are routinely predicted for foams without powdered urethane in slabstock plants around the world in the course of daily production. There are nearly as many predictive models as there are foam plants. These range from simple rules of thumb, to the valuable experience of skilled chemists and operators, to sophisticated spreadsheets and computer programs. Examples of the latter include the FoamKitä software , and the models presented by Schiffauer and coworkers . Our goal here is not to replace these methods, but to offer a flexible, simple, and physically meaningful way to add the influence of recycled powder to an existing model. That is, we aim to preserve the structure of the existing predictive method (which is often factory-specific) while accounting for the effects of powder.