Current Research Projects

Flame Retardants Using Natural Materials

Polymer Composites

Overview: Many flame retardants in use today have toxicity concerns, are persistent, have adverse environmental effects, have negative impacts on mechanical properties, or can leach out of products.  This creates a need for new flame retardants and flame retardant formulations.  We have recently used clay and carbohydrates to develop new flame retardants for use in both thermosets and extrudable thermoplastics. We have used a variety of natural sources to prepare our flame retardants, including dirt, wood, grapes, cereal grains, seaweeds, and arthropods.

Relevant Publications:

D. M. Fox, N. Kaufman, H. Khlafan, J. R. Shields, and R. D. Davis, “Plant-Based Flame Retardant Coating for Flexible Polyurethane Foam,” in Proc. Fire and Mater. 2017 Conf., Interscience Communications, Ltd., San Francisco, CA, 2017, 472-477.

D. M. Fox, M. Novy, K. Brown, M. Zammarano, R. H. Harris Jr., M. Murariu, E. McCarthy, J. Seppala, and J. W. Gilman, “Flame Retarded Poly(lactic acid) Using POSS-Modified Cellulose. 2. Effects of Intumescing Flame Retardant Formulations on Polymer Degradation and Composite Physical Properties,” Polym. Degrad. Stab., 2014, 106, 54-62.

D. M. Fox, J. Lee, C. J. Citro, and M. Novy, “Flame Retarded Poly(lactic acid) Using POSS-Modified Cellulose. 1. Thermal and Combustion Properties of Intumescing Composites,” Polym. Degrad. Stab., 2013, 98, 590-596.

D. M. Fox, R. H. Harris, Jr., S. Bellayer, J. W. Gilman, M. Y. Gelfer, B. S. Hsaio, P. H. Maupin, P. C. Trulove, and H. C. De Long, “The Pillaring Effect of the 1,2-Dimethyl-3(benzyl ethyl iso-butyl POSS) Imidazolium Cation in Polymer/Montmorillonite Nanocomposites,” Polym., 2011, 52, 5335-5343.

Projects:

  1. Carbohydrate Based Flame Retardants.
  2. Reinforcing Flame Retardants from Waste Musa.
  3. Agricultural Waste as Flame Retardants.

Coatings for Foam & Wood

Overview: Additional challenges arise when the flame retardant has to be incorporated in a coating.  Coatings are used for preformed materials such as foams, where the preparation is sensitive to the ingredients of the precursors; wood, where the material is made in nature; and steel, which is prepared at high temperatures.  Some of the challenges include the need for mechanical durability, washability, and strong interfacial adhesion.

Relevant Publications:

D. M. Fox, N. Kaufman, M. Colorado Escobar, E. Knowlton, J. F. Lomax, Y.-C. Li, Y. S. Kim, K. Hoffmann, and R. D. Davis, “One-pot, flame retardant coatings derived from natural materials. 1. Effects of carbohydrate functional groups on coating composition and flammability,” manuscript in preparation.

Projects:

  1. Protein Bound Flame Retardants with Reduced Leachability.
  2. Carbohydrate Based Flame Retardants.
  3. Coatings Using Polydopamine.

Natural Weathering of Flame Retardants

Overview: Leaching is one of the disadvantages to some of the flame retardants used today.  There currently is a lack of data on the long term durability of flame retardants when weathered naturally.  This information is critical not only for the application of flame retardants in outdoor environments, but also for the development of accelerated weathering models.  The best way to obtain this data is by placing flame retarded products in several outdoor environments of variable climate.  We have begun testing the natural weathering of flame retardants in epoxy and wood products.  Field sites in Virginia, California, and Florida will soon be established to provide a wide range of climate effects on the durability of the products.

Projects:

  1. Natural Weathering of Flame Retardant Treated Wood in National Forests.
  2. Natural Weathering of Epoxies Containing Intumescing Flame Retardants.

 

Cellulose Nanocrystals

Surface Modification

Overview: Cellulose nanocrystals have been hailed as the next generation nanomaterials for composites.  It is the most abundant biopolymer on earth, making it both renewable and sustainable.  Individual nanocrystals have greater stiffness than glass fibers and have strengths on the same order of magnitude as kevlar and steel.  Their advantage as reinforcing materials is increased when considering their low density.  As a result, they have been studied to “lightweight” materials, such as glass reinforced epoxy composites.   However, realization of their potential is hindered by their high levels of water absorption, low thermal stabilities, poor miscibility with non-polar polymers, and irreversible aggregation once dried.  We have developed a simple, affordable, and scalable method to simultaneously address these issues with a relatively low impact on the environment.

Projects:

  1. Effects of Cation on Cellulose Surface Energies and Water Absorption.
  2. Cation Selectivity on Cellulose Nanocrystals.
  3. Kinetics & Thermodynamics of Metathesis Reactions.

Relevant Publications:

B. Natarajan, C. D. Emiroglu, J. Obrzut, D. M. Fox, B. Pazmino, J. F. Douglas, and J. Gilman, “Dielectric Characterization of Confined Water in Chiral Cellulose Nanocrystal Films,” ACS Appl. Mater. Interfaces, 2017, 9, 14222 – 14231, DOI: 10.1021/acsami.7b01674.

Douglas M. Fox, Rebeca S. Rodriguez, Mackenzie N. Devilbiss, Chelsea S. Davis, Jeremiah Woodcock, Robert Sinko, Sinan Keten, and Jeffrey W. Gilman, “Ion Exchanged Cellulose Nanocrystals for Simultaneously Tailoring Surface Energies and Thermal Stabilities,” ACS Applied Materials & Interfaces, 2016, 8, 27270 – 27281, DOI: 10.1021/acsami.6b06083.

Polymer Composites

Overview: Our primary motivation to altering the surface energies of cellulose nanocrystals is to improve their dispersion in hydrophobic polymers.  We are examining both thermoset matrixes, such as epoxies, and thermoplatic matrixes, such as polystyrene and poly(lactic acid).

Projects:

  1. Bisphenol A Based Epoxies
  2. Styrenic Polymers
  3. Composites for 3-D Printing

Relevant Publications

D. M. Fox, M. Devilbiss, N. Kaufman, R. Rodriguez, J. Woodcock, C. S. Davis, J. W. Gilman, J. R. Shields, R. D. Davis, S. Matko, and M. Zammarano, “Epoxy Composites Using Wood Pulp Components as Fillers”, Chapter 11 in Composites from Renewable and Sustainable Materials, M, Poletto (Ed). InTech, 199-215, 2016, http://www.intechopen.com/books/composites-from-renewable-and-sustainable-materials/epoxy-composites-using-wood-pulp-components-as-fillers.

Green Solvent Characterization

Ionic Liquids

Overview: Ionic liquids are organic salts that melt below 100 °C. They have many unique properties and have gained interest as potential green solvents because they are non-volatile and potentially recyclable.  However, the accumulation and affect of trace impurities has not been studied extensively.  We have already examined their thermal properties and found that their long term thermal stability is not as high as originally proposed.  Further, we found that trace impurities can affect the thermal stability of the ionic liquid.  We are now investigating how the synthesis co-solvent can affect the purity of the ionic liquid product and how these impurities affect the physicochemical properties.

Relevant Publications:

D. M. Fox, J. W. Gilman, A. B. Morgan, J. R. Shields, P. H. Maupin, R. E. Lyon, H. C. De Long, and P. C. Trulove, “Flammability and Thermal Analysis Characterization of Imidazolium Based Ionic Liquids,” Ind. Eng. Chem. Res., 2008, 47, 6327-6332.

R. A. Mantz, D. M. Fox, J. M. Green III, P. A. Fylstra, S. Bellayer, J. W. Gilman, P. C. Trulove, and H. C. De Long, “Dissolution of Biopolymers Using Ionic Liquids,” Z. Naturforsch. A, 2007, 62, 275-280.

D. M. Fox, J. W. Gilman, H. C. De Long, and P. C. Trulove, “TGA decomposition kinetics of 1-butyl-2,3-dimethylimidazolium tetrafluoroborate and the thermal effects of contaminants,” J. Chem. Thermodynamics, 2005, 37, 900-905.

Projects:

  1. Counter-Ion Impurities from Metathesis Reactions.
  2. Solubility of Carbohydrates in Ionic Liquids with Co-Solvents.
  3. Solid – Liquid Phase Equilibria in Ionic Liquid Mixtures
  4. Recyclability of Ionic Liquid Solvents During Precipitation Reactions.

Plant Derived Solvents

Overview: There are a number of plant based solvents that have been used on the small scale for cleaning and solvent applications.  Pinene (found in turpentine and Pine-sol™), limonene (found in orange hand cleaners and Goo-gone™), and ethyl lactate (a fairly new solvent) are extracted or derived from natural products. For these solvents to gain increased use and application, knowledge of their physical, chemical, and solvent properties is essential.  We have focused primarily on ethyl lactate, which is a chiral solvent derived from corn with properties between that of ethanol (water soluble, grain alcohol) and ethyl acetate (water insoluble, nail polish remover).

Relevant Publications:

M. Ashraf, K. Tokarz, and D. M. Fox, “Temperature dependent thermal and solvent properties of ethyl lactate enantiomeric mixtures,” manuscript in preparation.

Projects:

  1. Ethanol – Ethyl Lactate Mixtures
  2. Epoxidized Limonene