Computational Analysis of Nonuniform Expansion in Polyurethane Foams

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Fluid Dynamics

Background:

• Experimentally observed disparities in polyurethane foam volumes across different geometries motivated this study.
• Local variations in thermal and rheological properties are hypothesized to cause foam expansion heterogeneity.

Purpose of the Study:

• To computationally investigate the heterogeneity in foam fraction distribution in chemically expanding blown polyurethane foam.
• To develop and validate mathematical models accounting for spatial inhomogeneity in foam expansion.

Main Methods:

• Utilized a continuum approach to model the reacting mixture.
• Formulated nonlinear coupled partial differential equations for flow.
• Employed finite-volume techniques for numerical solutions.
• Validated models with experimental data and micro-computed tomography (μ CT) scan analysis.

Main Results:

• Proximity to the external environment and thermal-diffusion layer thickness influence foam fraction distribution.
• Simulations demonstrated an average spatial variation of approximately 1.1% in solid foam fraction from walls to core.
• Results correlate with void fraction distribution within the foam matrix.

Conclusions:

• The developed computational models accurately capture spatial variations in foam fraction.
• Model predictions align favorably with experimental observations, enhancing understanding of foam expansion.
• This work provides insights into controlling foam properties through geometric and thermal considerations.