Factors Influencing the Smoldering Performance of Polyurethane Foam
Mauro Zammarano, Szabolcs Matko, Roland H. Kraemer, Rick D. Davis, Jeffrey W. Gilman, Shivani N. Mehta
The objective of this study was to evaluate whether polyurethane foam (PUF) could be produced as a standard reference material for ultimate use in a standard test intended to ensure the smoldering performance of commercially available upholstered furniture. For this purpose, PUF was produced by a commercial manufacturer and its smoldering propensity was evaluated. The experimental design was organized into four parts or Iterations. In Iteration 1, the results showed that smoldering intensity was dominated by foam morphology, which overrides effects of chemical composition for the range of polyols and surfactants studied here. In Iteration 2, the morphology of the foam was controlled by varying the processing parameters, i.e., tin catalyst content, water content and mixing head pressure. The results showed that smoldering increased with air permeability but a better morphological descriptor of the foam structure was required to fully characterize smoldering in the high permeability range (i.e., in PUF with a dominantly open-cell structure). In Iteration 3, it was determined that for these types of foams, smoldering was controlled by cell size. The feasibility of a reference material with well-characterized and reproducible smoldering is linked to the ability to manufacture an open-cell PUF with a well-defined cell size and density. In Iteration 4, scale-up from the pilot plant to the production line was considered. Foams with much more consistent properties (e.g., air permeability, density, cell size, etc.) throughout the bun of foam were fabricated in the production line as compared to the pilot plant. This allowed for the fabrication of PUFs with a very reproducible smoldering to be used as a potential standard reference material.