Functionalized silicone composites: omniphobic coatings, microspheres and plastic explosives

Silicones;Elastomers;Composites;Coatings;Microspheres;Energetic materials

Neelakantan, Nitin Krishna

关键词: Silicones;    Elastomers;    Composites;    Coatings;    Microspheres;    Energetic materials;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/97671/NEELAKANTAN-DISSERTATION-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Silicones are ubiquitous polymers containing a silicon-oxygen backbone and a variety of functional groups that can be tailored to very specific applications. Their flexibility, biocompatibility and relative inertness make them the ideal choice in materials as diverse as cosmetics, defoaming agents in food and medical implants. This thesis will focus on three separate projects, each one a silicone-based composite. Chapter 1 is an overview that includes a brief history, background, synthesis, applications, chemical structure, and any other relevant information regarding silicones. Chapter 2 describes the successful fabrication of a sprayable omniphobic coating that contains a polydimethylsiloxane binder and nanoparticle ZnO. A coating, or any other surface, is considered omniphobic if it is both water-repellent (i.e. hydrophobic) and oil-repellant (i.e. oleophobic). The coating herein was sprayed on a variety of different surfaces, such as metal mesh, filter paper and bare aluminum, rending them resistant to liquid contamination. The desired application of this coating is to promote efficient heat transfer in condensing pipes by preventing insulating oily films from forming on their interior. By keeping the surface free of films, more heat may be available for transport to the ambient environment.Chapter 3 describes the synthesis of silicone microspheres via ultrasonic spray pyrolysis. A viable route to silicone microspheres has eluded researchers for many years, in large part due to the very low surface energy of silicone polymers. This prevents a simple emulsion route; the surface energy promotes agglomeration, a problem which cannot be combatted effectively by common surfactants. Microfluidic devices are expensive and afford only low yield and even lower throughput. Thus, we have developed a simple route which nebulizes silicone precursors into micron-sized aerosol droplets and flows the droplets through a furnace tube, where curing and solvent evaporation take place. Since each droplet is its own micro-reactor, each produces a well-formed microsphere with ano observable agglomeration. Furthermore, we can tune the size and composition of these microspheres simply by altering the concentration and components of the precursor.Chapter 4 describes a series of experiments on silicone-based plastic explosives. There is a paucity of literature regarding the controlled shock impact and subsequent detonation of commonly used explosives. What reports exist rely on computer-modelling and idealized assumptions to make conclusions about the thermomechanical and chemical nature of these events. When an actual explosive is used, it is often loosely packed powder which is of low density and contains many pores and defects. We have devised a method that uses mild-impact sources to generate explosions in a very small amount of explosive material. We incorporate instrumentation that allows us to see, with nanosecond resolution, the temperature and spectral emission of this explosive, under real-life impact conditions.