Predicting Bubble Size Distribution in Polyurethane Foam through Nucleation and Bubble Growth Modeling

Polyurethane (PU) foams are extensively used in industry due to their ease of processing, insulation efficiency and structural stability. The process of making PU foams involves the reaction of isocyanates with water to make carbon dioxide that generates foam bubbles; called the “blowing” reaction. Additionally the “gelling” reaction, between isocyanate and polyol, is responsible for make polyurethane linkages that provide structural stability. The relative rates of gelling and blowing reactions along with several other parameters such as use of surfactants, catalysts, reactivity of polyols, water content as well as operating conditions determine the final foam properties. Therefore, developing next generation PU insulation material relies on understanding the effect of the material properties and processing conditions on final insulation properties, including bubble size distribution and porosity. A numerical model that simulates nucleation and bubble growth in free-rise PU foams is presented here. Nucleation is based on classical nucleation theory and the influence volume approach has been leveraged to model the bubble growth. By solving the mass, momentum and species balance equations, the model can predict the bubble size distribution and porosity of free-rise PU foams.