Physicochemical Properties of Polymeric Materials

Polymeric materials that act as fuels and oxidizers are composed of nitrogen, oxygen, carbon, and hydrogen atoms. The hydrocarbon structures act as fuel components, and the oxidizer fragments, such as -C-NOj, -O-NOj, -O-NO, or -N-NO2, are attached to the hydrocarbon structures through covalent chemical bonds. 

Polymeric materials are used as binders to hold sohd particles together so as to formulate composite explosives or composite propellants. The polymeric materials also constitute part of the fuel ingredients when the crystalline particles are oxidizer-rich. Various types of hydrocarbon polymers are used as polymeric binders. 

Three types of polymeric materials are used inert polymers, active polymers, and azide polymers. No exothermic heat is produced when inert polymers are decomposed thermally. On the other hand, exothermic reactions occur when active polymers and azide polymers are decomposed. Self-sustaining burning is possible when active polymers and azide polymers are ignited. 

Nitrate esters are characterized by the -0-N02 bonds in their structures. Typical nitrate esters used for propellants and explosives are nitrocellulose (NC), nitroglycerin (NG), triethyleneglycol dinitrate (TEGDN), trimethylolethane trinitrate (TMETN), and diethyleneglycol dinitrate (DEGDN). These nitrate esters are all liq- 

NC decomposes by an autocatalytic reaction which evolves N02 gas due to the breakage of the weakest bond of -0-N02. The reaction between 363 K and 448 K is first order and the activation energy is 196 kj/mol. The remaining fragments form aldehydes such as HCHO and CH3CHO. The reaction between N02 and aldehydes produces heat and combustion gases. 

NG has a relatively low molecular mass, 227.1 kg/kmol, is liquid at room temperature, and becomes a solid state below 286 K[1,21. Since NG is shock sensitive and easy to detonate, desensitizers are admixed for practical applications. NG is one the major ingredients used for propellants and explosives. Typical examples are doublebase propellants mixed with nitrocellulose, and dynamites mixed also with nitrocellulose and/or other crystalline materials. The autocatalytic decomposition of NG, occuring at 418 K, is caused by the bond breakage of -0-N02 and evolves N02 with an activation energy of 109 kj/mol. The self-ignition occurs after a critical concentration of N02 is achieved at 491 K. 

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Determination of Homopolymer Molecular Weights Understanding the structure and physicochemical properties of polymeric materials is essential... 

Depending on the distribution of micro/nanofiller in the polymer matrix, the composites may be classified as microcomposites or nanocomposites. These two types of composites differ significantly with respect to their properties. The nanocomposites show improved properties compared to pure polymer or that of microcomposites. It started only back in 1990, when Toyota research group showed that the use of montmorillonite can improve the mechanical, thermal, and flame retardant properties of polymeric materials without hampering the optical translucency behaviour of the matrix. Since then, the majority of research has been focused in improving the physicochemical properties, e.g. mechanical, thermal, electrical, barrier etc. properties of polymer nanocomposites using cost effective and environmental friendly nanofillers with the aim of extending the applications of these materials in automotive, aerospace, construction, electronic, etc. as well as their day to day life use. The improvements in the majority of their properties have invariably been attributed... 

Physicochemical properties of polymeric NPs affecting their toxicological profile Physicochemical parameters of polymeric NPs such as size, material, shape, surface properties, or the presence of ligands may result in different kinetic properties when administered orally... 

From the technological point of view, UV laser treatment makes it possible to alter in a controllable marmer the physicochemical structure of polymeric materials, leading to interesting modifications of surface properties, such as better wettability [53, 54, 58], adherence [53-55], and printability [53]. In the meantime, treatment with higher power lasers leads to a significant increase of the surface temperature [59]. 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

As described in Sections 4.2.4.1 and 5.2.2, GAP is a unique energetic material that burns very rapidly without any oxidation reaction. When the azide bond is cleaved to produce nitrogen gas, a significant amount of heat is released by the thermal decomposition. Glycidyl azide prepolymer is polymerized with HMDI to form GAP copolymer, which is crosslinked with TMP. The physicochemical properties of the GAP pyrolants used in VFDR are shown in Table 15.3.PI The major fuel components are H2, GO, and G(g), which are combustible fragments when mixed with air in the ramburner. The remaining products consist mainly of Nj with minor amounts of GOj and HjO. 

In starting a residue analysis in foods, the choice of proper vials for sample preparation is very important. Available vials are made of either glass or polymeric materials such as polyethylene, polypropylene, or polytetrafluoroethylene. The choice of the proper material depends strongly on the physicochemical properties of the analyte. For a number of compounds that have the tendency to irreversible adsorption onto glass surfaces, the polymer-based vials are obviously the best choice. However, the surface of the polymer-based vials may contain phthalates or plasticizers that can dissolve in certain solvents and may interfere with the identification of analytes. When using dichloromethane, for example, phthalates may be the reason for the appearance of a series of unexpected peaks in the mass spectra of the samples. Plasticizers, on the other hand, fluoresce and may interfere with the detection of fluorescence analytes. Thus, for handling of troublesome analytes, use of vials made of polytetrafluoroethylene is recommended. This material does not contain any plasticizers or organic acids, can withstand temperatures up to 500 K, and lacks active sites that could adsorb polar compounds on its surface. 

Polymeric nanoparticles have attracted a lot of attention in the last years. Polymeric materials exhibit several advantageous properties including biodegradability and ease of functionalization. They also allow for a greater control of pharmacokinetic behavior of the loaded drug leading to more steady levels of drugs (Rawat et al. 2006). Furthermore, they enable the modulation of the physicochemical properties of the surface such as Zeta potential and hydro-phobicity/hydrophilicity. Many polymers used to develop nano- and... 

The synthesis of nanocapsules can best be obtained in miniemulsion using different approaches [107], One possibility is based on the phase separation process within a droplet during the polymerization [108], Here, vinyl monomers were polymerized in the presence of a hydrophobic oil. During the polymerization, the polymer becomes insoluble in the oil, leading to a phase separation. With properly chosen physicochemical properties of monomer and encapsulated material, a polymeric shell surrounding the liquid core can be formed. 

A common approach to the study of properties, in particular variations of properties under external effects, should include, as one of the basic ideas, the conception of polymeric foams as heterogeneous systems with developed surface (see Chap. 5.4). As became apparent in the early 1970 s, the specific surface of these materials is of the order of dozens and even hundreds of square meters per gram Such high values of the specific surface are quite exceptional among polymeric materials and lead to marked (in relation to expected) changes in several physicochemical properties of plastic foams, for example water absorption and resistance to thermal oxidation. 

F. A. Cotton. He moved to Northwestern University as an assistant professor In 1970. His research Interests Include synthetic and mechanistic f- and d-element organometallic chemistry, particularly with applications In olefin polymerization catalysis, as well as the design, synthesis, and physicochemical properties of unususal molecules and molecule-derived materials. 

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