In this project, fire barrier layers (FBs), which rely on physical rather than chemical mechanisms of action, are investigated to enable low flammability products without using FRs.

Fire retardants (FRs) have been subject to rising scrutiny over the past several decades, due to growing concern with regards to the environmental and human health hazards that they pose. There are also reports indicating that FRs compounds may result in marginal reductions in flammability. Consequently, the use of FRs has been restricted or, in certain applications, completely banned. This lead to a  broad but incorrect  perception that - without FRs - polymer containing products cannot comply with open-flame test methods and regulations.  

The PRINCIPAL OBJECTIVE of this project is to enable low flammability products which do not contain FRs by providing 1) a methodology and guidance to assess FBs performance at bench-scale 2) enable the development of FBs with improved performance, 3) explore the use of FBs in multilayered products for high/medium-impact applications identified by NIST research roadmap. 

The project will focus on multilayered products with high priority for residential fire research [1]. Residential upholstered furniture (RUF) remains as the highest priority now and, if not resolved, will likely remain the highest priority in the future. Besides RUF, other applications of high priority include resistance to exterior fire exposure in buildings, durable and non-toxic fire safe cross-cutting solutions, multi-layered composites, etc.

NIST recently developed a bench-scale test based on the cone calorimeter, hereafter referred as the “Cube test”. The Cube test has been designed to measure heat release rate accounting for mass and heat transfer of pyrolysis products in a representative cross-section of a multi-layer product, possibly including a fire barrier [2]. The Cube test yields additional information to cone calorimetry, including propensity of the product to generate a pool fire and propensity to burn-through in presence of fire barriers. These additional data have been proved to be useful to predict the full-scale performance of multi-layered products containing fire barriers [3]. A strong linear correlation (R2 > 0.97, where R is Pearson’s correlation coefficient) has been found between selected performance parameters at full-scale (i.e., peak of heat release rate, time to peak of heat release rate and average heat release rate before ignition of liquid products) and Cube test parameters.

The Cube test will be further developed in this project to (a) investigate its correlation with full-scale testing of multilayered products, (b) enable the development of FBS with improved performance and (c) explore the use of FBs in multilayered products for high-impact applications.

[1] Davis, R. D., et al. (2018). NIST Special Publication 1220 Workshop Report: Research Roadmap for Reducing the Fire Hazard of Materials in the Future. National Institute of Standards and Technology Special Publications. Gaithersburg, MD. https://www.nist.gov/publications/workshop-report-research-roadmap-reducing-fire-hazard-materials-future         

[2] Zammarano, M, Shields, JR, Leventon, I, et al. Reduced-scale test to assess the effect of fire barriers on the flaming combustion of cored composites: An upholstery-material case study. Fire and Materials. 2021; 45: 114– 126. https://doi.org/10.1002/fam.2910

[3] Zammarano, M. (2021). Fire Performance of Upholstery Materials: Correlation between Cube Test and Full-Scale Chair Mock-Ups. https://doi.org/10.6028/NIST.TN.2194