Reduced Ignition and Flame Spread with Nano-Engineered Foam Project

This research will enable commercialization of a reduced flammability, inexpensive, and EHS^[1] compliant polyurethane foam and a high smoldering SRM foam to be used in standardized flammability tests.  This will be accomplished by (a) evaluating a cost-effective and commercially viable nanoparticle coating technology to create a fire blocking armor on foam, (b) determining how to reduce foam flammability by controlling the foam characteristics and the manufacturing process, and (c) developing validated tools that enable EHS assessment of the nanoparticle-rich coatings in the workplace and residence.

[1] Environmental, health, and safety (EHS).  Only halogenated fire retardants are used in polyurethane foam.  This class is under increased regulation due to potential EHS concerns.  If banned, there are no commercially viable fire retardant alternatives for foam.

Objective:  By 2014, to develop the measurement science that enables (1) design and manufacture of low hazard soft furnishings through commercialization of low heat release, inexpensive, and EHS compliant nanoparticle-based fire retardant foam, (2) the assessment of EHS attributes of nanoparticles, an innovative fire retardant technology for any polymer systems, and (3) development of a reproducibly high smoldering standard reference polyurethane foam.

What is the new technical idea?  This research will reduce the flammability of polyurethane foam to the extent that it becomes a cost-attractive alternative to comply with flammability regulations and will enable EHS assessments^[2] of this innovative fire retardant (FR) foam.  There are two approaches being taken to reduce foam flammability.  One approach is to evaluate nanoFR/LbL^[3],[4] coatings as a technology to reduce the high, total, and rapid heat release of polyurethane foam.  This includes characterizing the architectures of the nanoFR and the LbL coating and determining attributes of the LbL process (e.g., pH value, FR surface chemistry, foam air flow) that result in the greatest reduction in foam flammability and nanoFR release.  Existing measurement tools lack the necessary spatial resolution; therefore, this project will also develop new measurement tools to characterize these architectures (e.g., FRET)^[5].  The other approach is to identify the foam characteristics and the manufacturing process parameters^[6] that control foam flammability as this knowledge will enable commercialization of lower flammability foam without using any FR.  This knowledge will also be used to develop a high smoldering SRM foam that facilitates the evaluation of the nanoFR/LbL technology and may be used in region or national flammability regulations and tests^[7].  The other part of this project is to develop the measurement science that enables others to determine if this nanoFR/LbL technology is an EHS compliant^[8] and, therefore, commercially viable.  This project will provide agencies^[9] with released materials that they will use to develop risk exposure models and define nanoparticle exposure threshold limits.^[2]

What is the research plan?  This project will be separated into three research tasks with the completion of each task being critical to meeting the overall project objective.  Each task will have an impact on fire losses.

Task 1 will evaluate and deploy nanoFR/ LbL fire retardant coatings as a cost-effective and commercially viable approach to reduce the fire hazard of foam.  In year 1 (FY12), we identified and quantified factors of the coating process and recipe that impact coating growth rate, morphology, and foam flammability then used this knowledge to develop a clay-based coating that reduced the peak heat release rate of PUF by ~35% and the average HRR value by 75%.  In year 2 (FY13), this year 1 knowledge will be used to evaluate other coating recipes with the focus on improving both Cone measured properties and flame spread properties, and reducing the number of layers needed for flammability reduction.  We will continue to evaluate novel tools to identify the micro- and macrostructure architecture (e.g., FRET^[5]) of the nanoFRs and the LbL coatings that control foam flammability (measured in Task 2) and nanoFR release (measured in Task 3).  In year 3 (FY14), this technology will be shared with stakeholders (e.g., FXI Foams, Albermarle, and Polyurethane Foam Association) and will continue to be evaluated based on stakeholder input of the measurement science gaps to address before nanoFR/LbL can be deployed for foam applications.  NanoFR/LbL foams for bench scale/mock-up flammability testing will be fabricated in year 2 or 3.^[10]

Task 2 will develop and deploy a SRM foam and validated tools to measure foam flammability.  The  well-defined characteristics of a SRM foam and the accuracy of the validated testing tools are essential for the evaluation of the nanoFR/LbL technology on foam (Task 1) and may be of value in standardized testing of foam containing products.  In year 1 (FY12), we determined the factors critical to controlling foam smoldering performance (e.g., cell size and air flow) and defined attributes that were critical to achieving sufficiently high smoldering^[11]. We helped a foam manufacturer demonstrate that this foam can be produced on a pilot plant scale and in June 2012, had a SRM foam available for purchase (SRM 1202 Fabric Smoldering Ignition Testing Materials).  In year 2 (FY13), we will determine what parameters and what values are required to yield foam with different levels of smoldering performance and maintain SRM 1202.  In year 3 (FY13) we will continue to support and maintain SRM 1202.  

Task 3 will develop and deploy validated tools to collect, quantify and characterize nanoFRs released during manufacturing, in-service, and pyrolysis of nanoFR foam.  In year 1 (FY12), we developed and utilized a spectroscopic technique to quantify nanoFR release from foam as a function of stressing conditions and purchased a new tool (scanning particle mobility analyzer, SMPS) and designed and built an adjoining environmental chamber to quantify nanoFR release from char.  Additionally we developed a collaboration with CPSC and Duke University^[12] to access the potential EHS impact of released nanoFR.  In year 2 (FY13), the information and materials generated from year 1 and 2 will be given to Duke for developing a risk assessment model and for NIST to access the durability of the nanoFR/LbL technology (Task 1).  A database of nanoFR release from products and char will be developed based on results from the SPMS and environment chamber.  In year 3 (FY14), the SMPS with the environmental chamber will be validated against other routine measurement techniques and transferred (along with the other knowledge gained from this Task 3) to stakeholders (e.g., CPSC and EPA).

[2] Global regulations restricting chemicals are based on toxicity measurements and the development of risk exposure models, which are outside the scope of this project as these are activities performed by regulating agencies or performed by other groups in accordance to the regulator’s requirements.

[3] NanoFR/LbL is nanoparticle fire retardant coating creating using Layer-by-layer assembly.  LbL assembly is a water-based process to fabricate coatings on a substrate that are constructed of several nanometer thick polymer layers of opposing charges, which may contain additives (e.g., FR).  This process is only commercially used for applying adhesives to tapes and in electronic circuit boards where the substrate geometry is essentially two dimensional and simple.

[4] Development of innovative technologies to develop cost-effective fire-safe materials is listed as a critical cross cutting strategic focus area that has the potential to simultaneously impact several aspects of the national fire problem (Draft Measurement Science Roadmap for Innovative Fire Protection).  LbL assembly and nanotechnologies are listed as innovative technologies that need to be developed, and soft furnishing and foam are listed as products needing innovative fire safe approaches.

[5] Förster resonance energy transfer (FRET) combined with laser scanning confocal microscopy (LSCM) to measure the amount and quality of the interface between nanoFR and polymer, LbL layers and substrate, etc.  This is a new technique being developed jointly between Fire Research and Polymer divisions.  There are significant measurement science issues to address (e.g., appropriate dye tags, and detector and laser resolution).

[6] Foam manufacturers alter their process and formulations to meet selling specifications (e.g., color and firmness).  These changes will alter other foam characteristics (e.g., air flow and surface energy), which have unknown and perhaps inconsistent impact on the foam flammability and the effectiveness of FR technologies. 

[7] Consumer Product Safety Commission (CPSC) 16 CFR 1634 is a proposed regulation for limiting the flammability of upholstered furniture.  The regulation is based on using a chair mock-up (not a fully built commercial chair) and is primarily focused on restricting/approving cover fabrics that result in failing/meeting the specified flammability metrics.  This SRM could be used CPSC 16 CFR 1634.

[8] Strategy for Nanotechnology-Related Environmental, Health and Safety Research report by National Science and Technology Council Committee indicates a critical gap in accessing the toxicity of the released materials and developing risk models of exposure is accurate and highly sensitive nanoparticle measurement tools and collection of actual release materials (both of which are addressed in this proposal).

[9] CPSC and OSHA are considering regulating the release of nanoparticles during manufacturing and in-service, respectively, from consumer products, but lack the measurement science needed to determine if it is necessary.

[10] Mock-up flammability testing will be conducted either in this or Pitt’s Upholstered Furniture project.

[11] A high smoldering foam enables regulations to be developed based on a worst case fire risk scenario.

[12] Duke University is the leader for the EPA and NSF funded Center for the Environmental Implications of Nanotechnology (http://www.ceint.duke.edu/) and is tasked with developing the risk assessment models for the use of nanoparticles.

Recent Results:

Outputs:

• 9 publications with 3 more likely to be published by the end of FY12^[13]
• New knowledge for specific end-use application of LbL; first to:
• • develop a non-halogenated and viable FR technology for foam.
  • develop a self extinguishing PUF using the nanoFR/LbL technology. 
  • demonstrate a 35% reduction in PHRR and 75% reduction in average HRR using nanoFR/LbL technology (better than any commercial technologies).
  • determine the correlation of fast coating growth with polymer and nanoFR concentration and the impact it has on foam flammability.
  • develop a LbL coating using MWCNT and CNF and demonstrate the impact on flammability.
  • demonstrate that flammability reduction strongly depends on adhesion of coating to foam.
  • demonstrate that the foam attributes can be removed from impacting coating and flammability performance by pretreating to improve coating adhesion. 
• New knowledge correlating foam smoldering performance with cell size, cell size distribution, and amount of surface area, which will enable us to move forward with developing an SRM foam.
• Coauthor (FY2012) of Risk Science Innovation and Application report on Multi-walled Carbon Nanotubes in Polymer Release Measurement Methods – This document provides guidance on methods to understand and quantify the release of nanomaterials used in products, specify research gaps, and to develop standardization of methods to cause and measure the release of nanomaterials.
• Working with two manufacturers who are considering the nanoFR/LbL coating technology.

Impacts:

• Developed a standard reference foam.  SRM 1202: Fabric Smoldering Ignition Testing Materials. (FY2012)

Standards and Codes:

Project team members are participating in a select number of key standards, codes, and regulatory committees:

• ASTM  E5.15: Contents and Furnishings. Gann is Task Group Chair and has shared information showing that foam flammability can be reduced using the nanoFR coatings.
• CPSC 16 CFR 1634: Upholstery Furniture Regulation. Davis provides technical guidance on the testing methodology and materials, and through this project leads the development of this technical basis.  The SRM 1202 may potentially be used in this regulation.
• CPSC: Nanoparticle Regulations in Consumer Products: Davis provides technical materials and technical guidance to CPSC and collaborators that are conducting risk assessments of nanoparticles used in soft furnishings. Davis will contribute to the technical component of a regulation restricting use of nanoparticles in these consumer products if CPSC decides to proceed based on the finding of risk assessments.  Decision point for moving toward regulating is expected within the next 18 to 24 months.
• EPA’s Decabromo and Hexabromo Fire Retardant Replacement Committees: Davis is a voting member of the steering committees that are evaluating EHS compliant and commercially viable alternatives for these “restricted or banned use” fire retardants and is coauthoring EPA regulatory guidance documents for these fire retardants.
• National Nanoparticle Initiative: Davis is a member of this multiagency committee and several of it subcommittees that are developing standardized approaches for accessing nanoparticle EHS and a roadmap for all nanoparticle research conducted by Federal agencies. The results of these committees will be the formation of national regulations on the handling, storage, and use of nanoparticles.

[13] 

1. Kim Y.S, Davis R, Cain A.A, Grunlan J.C., Development of layer-by-layer assembled carbon nanofiber-filled coatings to reduce polyurethane foam flammability, Polymer (2011) 52(13):2847-2855.
2. Li,Y.C., Mannen, S., Schulz, J., Grunlan, J.C., Growth and fire protection behavior of POSS-based multilayer thin films, Journal of Materials Chemistry (2011) 21:3060.
3. Davis, R. D., Y. S. Kim, et al. (2011). NISTIR 7805: Exposure and Assessment of Nanoparticle Containing Fire Retardant Consumer Products. NIST, NIST: 57.
4. Uddin, N., M. Nyden, et al. (2011). "Characterization of Nanoparticle Release from Polymer Nanocomposites Due to Fire." Fire and Materials.
5. Kim, Y. S. and R. D. Davis (2012). "Durable Nanoparticle Coatings to Reduce Polyurethane Foam Flammability." 243rd American Chemical Society Preprints.
6. Li, Y.-C. and R. D. Davis (2012). "Self-extinguishable Non-toxic Layer-by-Layer Coating on Flexible Polyurethane Foam." 243rd American Chemical Society Preprints.
7. Zammarano, M., S. Matko, et al. (2012). "Flexible Polyurethane Foam with Well Characterized and Reproducible Smoldering." 243rd American Chemical Society Preprints.
8. Li, Y. C., S. Mannen, et al. (2011). "Intumescent all-polymer multilayer nanocoating capable of extinguishing flame on fabric." Adv Mater 23(34): 3926-3931.
9. Laufer, G., C. Kirkland, et al. (2012). "Clay-chitosan nanobrick walls: completely renewable gas barrier and flame-retardant nanocoatings." ACS Appl Mater Interfaces 4(3): 1643-1649.