Seton Hall University eRepository @ Seton Hall Seton Hall University Dissertations and Theses (ETDs) Seton Hall University Dissertations and Theses Spring 4-29-2020 Surface Chemistry and Surface Properties of Energetic Nitrocellulose (NC) Henry Grau [email protected] Follow this and additional works at: https://scholarship.shu.edu/dissertations Part of the Analytical Chemistry Commons, Materials Chemistry Commons, Organic Chemistry Commons, and the Physical Chemistry Commons Recommended Citation Grau, Henry, "Surface Chemistry and Surface Properties of Energetic Nitrocellulose (NC)" (2020). Seton Hall University Dissertations and Theses (ETDs). 2762. https://scholarship.shu.edu/dissertations/2762 Surface Chemistry and Surface Properties of Energetic Nitrocellulose (NC) By: Henry Grau Dissertation submitted to the Department of Chemistry and Biochemistry of Seton Hall University in partial fulfillment of the requirements for the degree of Doctor of Philosophy April 2020 Seton Hall University South Orange, New Jersey © 2020 (Henry Grau) Seton Hall University College of Arts and Sciences Department of Chemistry and Biochemistry APPROVAL FOR SUCCESSFUL DEFENSE Henry Grau has successfully defended and made the required modifications to the text of the doctoral dissertation for the Ph.D. during this Spring Semester 2020. Dissertation Committee (please sign and date beside your name) The mentor and any other committee members who wish to review revisions will sign and date this document only when revisions have been completed. Please return this form to the Office of Graduate Studies, where it will be placed in the candidate’s file and submit a copy with your final dissertation. Dedicated to my family: My wife Sandy My daughter Sadie My son Trent Abstract This research describes an investigation into the wettability of nitrocellulose (NC), most importantly to nitroglycerin (NG), which are key components of formulations used to propel military ammunition. NG demonstrates complete wetting of NC and, overtime, NG sweats on the NC surface and leaks out. The leaking out of NG from the solid formulation is a known cause of fires and explosions resulting from storage. The origin of this research is inspired by the need to engineer a solution to leakage problems of energetic plasticizer in NC based propellant. While searching for a viable material for a specific application, we journeyed into the very specific details of the properties of NC, and the chemical structures used for surface functionalization. In Chapter 1, we discuss the properties of nitrocellulose and the classes of propellant that contain NC and NG. We discuss the significance of the contact angle and how it’s measured. Experimental data showing the surface tension of nitroglycerin and its use as a probe fluid is described. In Chapter 2, silane surface chemistry and its applications are discussed. We described reactions from previous work involving cellulose that assisted us with work with NC. We discuss our results from reacting alpha cellulose and silyl isocyanate that provided conformation for further applications with NC. We explain experiments for functionalizing NC using acyl chlorides and isocyanate chemistry. We then proceed with our findings that allowed us to establish chemical designs described in the following chapter. We describe approaches for producing a ‘tunable’ NC surface that is derived from a two-step process using the reaction of 3-(triethoxysilyl-propyl) isocyanate followed by reactions with alkyl-, fluoroalkyl-, or phenyl-silane, producing NC surfaces ranging in lyophobicity. Each functional group allows various degrees of reduced wettability of NC with NG. We vi demonstrate surface preparation using tetramethoxysilane and polydimethysilane vapor reactions on solid state NC. We further functionalized the silanol rich solid state NC with alkyl and fluoroalkyl functionalities. In Chapter 3, the progress of reactions is demonstrated by chemical analysis. SEM analysis of modified NC materials suggests bulk properties of NC were not affected by silane. DSC demonstrated consistent decomposition of bare and treated NC. XPS provided evidence of chemically modified fibers. Increased lyophobicity of modified NC demonstrate thermal stability and equivalent energetic properties compared to bare NC. NC was characterized by dynamic contact angles using water, hexadecane, and NG as probe fluids. Wettability of modified NC demonstrated significant variations in surface energy in accordance with the nature of surface functionalities. In Chapter 4, we discuss the methods of measuring contact angles. The contact angles of modified NC demonstrated surfaces with “tunable” wetting. NC grafted with fluoroalkyl-groups showed the most NG- o o repelling properties (θAdv/θRec ~90 /50 ). Estimation of contact angles on nitrocellulose treated fibers allowed insight of the surface properties showing an increase in curvature and reduced capillary effect. Surface energy was estimated using contact angle measurements. In Chapter 5, nitrogen gas adsorption gives insight on textural properties of bare and treated NC. Key words: Wetting and contact angle, Nitrocellulose, Nitroglycerin, Surface functionalization, Silane coupling agents, Surface energy, Energetic materials, Fiber analysis, XPS, Adsorption. vii Acknowledgements I would like to thank the following individuals for their support, teachings, and friendship. Dr. Alexander Y. Fadeev: Thank you for taking me on and showing me a whole new world of chemistry. You do things the ‘old school way’. The way academics and research should be done. I remember a meeting we had before my matriculation exam, I could not answer what should have been a simple chemistry question and you let me ‘have it’ for a good hour. You may not realize how that woke me up and helped me excel in my work, but it did. Thank you for that. Thank you for allowing me to pursue the PhD degree on a part-time basis so I could work full time. I am forever thankful for your help. Matriculation committee: Thank you Dr. Gorun, Dr. Sabatini, Dr Kazakevich, and Dr. Sabatini. You took the time to help me get through the matriculation process and agreed to read my dissertation. Seton Hall University Chemistry Department Staff and Students: While at SHU I heard time and time again how everyone is so ‘nice’ and how everyone at SHU treats each other with respect. This holds true. The first day I visited SHU as a PhD student, I met Dr. Marzabadi. She really took the time to talk to me and answer my many questions. She was very gracious. I must say, to this day she is the nicest college professor I’ve ever met. Thank you to Dr. Maloy, who took the time out to help me with statistic questions as well as my matriculation exam. viii Picatinny Arsenal: I would like to thank my employers and my management at Picatinny Arsenal for funding and allowing me to pursue my PhD. I would like to thank Bill DePiero for giving me a chance to advance my career. I would like to thank Ed Cooke who was always willing for me to pick his brain. Most of all, I would like to thank Alex Gandzelko. He was always willing to help me out with some tough problems. I will be forever grateful. ix Table of Contents Chapter 1: Nitrocellulose, Nitroglycerin, Propellant, and the Importance to Understand their Surface Chemistry ..................................................................................................................... 1 1.1 Introduction ................................................................................................................ 1 1.2 Nitrocellulose and its Properties ................................................................................ 2 1.3 Nitrocellulose Double Base Propellants ..................................................................... 4 1.4 Nitrogylcerin Migration in Solid Propellant and Possible Solutions ......................... 6 1.4.1 Co-extruded Propellant and the Lyophobic Barrier ............................................ 7 1.5 Nitroglycerin Wetting Properties & Surface Tension at Various Temperatures ....... 10 1.5.1 The Young’s Equation and the Contact Angle .................................................. 10 1.5.2 Experimental ..................................................................................................... 14 1.5.2.1 General Information .................................................................................. 14 1.5.2.2 Nitroglycerin Purity ................................................................................... 15 1.5.2.3 Wetting and Contact angles ....................................................................... 15 1.5.2.4 Surface Tension of Nitroglycerin .............................................................. 16 1.6 Results and Discussion ............................................................................................. 16 1.7 Conclusions .............................................................................................................. 20 Chapter 2: Approaches for Nitrocellulose Functionalization ................................................. 22 2.1 Introduction .............................................................................................................. 22 2.2 Cellulose: Its Role in Understanding Nitrocellulose Surface Functionalization...... 23 2.3 Silane Chemistry for Surface and Polymer Modification ........................................ 24 2.4 Cellulose Surface Modification ...............................................................................