Unfortunately, the majority of the polymer investigations cited have been performed under the classic conditions of slow heating rates or isothermal conditions in vacuum environments. However, the residence time of a polymer element at the solid surface during the normal ignition and combustion of a propellant is usually in the order of milliseconds. Further more, the pressure level is normally several hundred pounds per square inch in most actual combustion environments. Then the direct application of the low-pressure isothermal decomposition data to the propellant combustion may be questionable [34, 35].
Thermogravimetry (TG) has been extensively used for the determination of the thermal decomposition kinetics of polymeric binders. The kinetic
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Thus, the AP deflagration may be a well controlling factor for propellant burning rate. The deflagration of pure AP has been investigated intensively in an effort to gain a basic understanding of this process and hence of the combustion of rocket propellants which contain AP as the oxidizer. These studies have proceeded along two directions. The first concerned with investigation of pressure, additives and added radiant energy effects on the burning rate. The second study the deflagration process chemistry [33]. AP undergoes self-sustained combustion only at certain pressure ranges, giving rise to pressure limits. The existence of non-deflagration pressure range where steady deflagration does not occur is one of the most interesting aspects of AP deflagration which has so far managed to elude explanation. Generally, such a range is found to be below a certain pressure level known as the low-pressure deflagration limit (LPL) and above a certain pressure level known as upper-pressure deflagration limit (UPL). The LPL has greater practical importance and has been the subject of many studies. On the other hand, the UPL has not been systematically studied and supposed to exist at the upper level of combustion (detonation). According to many investigations, the average value of LPL was detected to be about 20 atm and burning rate under this condition is around 0.2-4.3 cm/s for single AP crystals or high density pellets. It was found that the LPL is insensitive to sample size and inert atmospheres. LPL increases as the (single) particle size is decreased, lowers as pre-heating, rises as pre-cooling, decreases with increasing pellet density and burning surface area [26, 36]. For more understanding, at sufficiently high pressures the energy transmitted from the flame towards the surface maintains the surface temperature above the AP melting point.
OH 27000 J/g. Hexane C H 35000 J/g. Variables:.. The variables used in this experiment are: Volume of water, mass of fuel, temperature of water, height of tube. height of flame, type of fuel, time it takes, width of flame, colour. of flame, material of container, size and surface area, purity of.
The most common form of polyethylene is petroleum based or olefins based; as before mentioned polyethylene compounds have a wide commercial applicability and are made from non-renewable resources (Harding, Dennis, von Blottnitz, Harrison, & S.T.L., 2007). Its manufacturing processes are regarded as energy intensive and release significant amount of CO2 and heat into the atmosphere (Broderick, 2008). Next a little more detailed description of polyethylene’s production processes will be presented, with a focus on the way the material inputs are extracted and synthesized.
Something that we all know for a fact, is that technology is a very powerful and advanced tool. There are thousands of different kinds of technologies and the extraordinary part about it is that they are all geared towards improving the human condition in the 21st century. One of them is called a thermal imager. Thermal imagers allow officers to detect heat signatures that were previously invisible to the naked eye. In other words, they are able to detect heat that is escaping a home. Police officers should have the right to use a thermal imager without a warrant because they are only able to see the exterior of a home, they they are only capable of detecting heat, and do not interfere with your private life because they cannot see you inside of your home.
Determination of the Enthalpy Change of a Reaction. Determine the enthalpy change of the thermal decomposition of calcium carbonate by an indirect method based on Hess' law. Determination of the Enthalpy Change of a Reaction. Determine the enthalpy change of the thermal decomposition of calcium carbonate by an indirect method based on Hess' law. Using the proposed method of obtaining results, these values were gathered.
Thermistor Investigation Aim: For this experiment I am going to investigate the variation of the resistance of a thermistor with different temperatures. The resistance will be tested at approximately every 10 degrees, with a range from 80 C down to 30 C, and these results will be recorded. After recording the results, the experiment will be repeated at a total of 3 times, this is so we can get an average that should be correct and accurate. Scientific Knowledge: Thermistors are thermally sensitive resistors and have, according to type, a negative (NTC), or positive (PTC) resistance/temperature coefficient. A thermistor is a type of resistor whose resistance changes significantly when its temperature changes.
Bruce Mattson. “Henry Cavendish 1731-1810”. History of Gas Chemistry. Updated September 25, 2001. Retrieved December 1, 2011
There are many types of polymer degradation mechanisms: thermal, mechanical, photochemical, radiation chemical, biological and chemical degradation (Schnabel, 1981). According to ASTM definition, “degradable plastics are the plastics that are designed to undergo a significant change in its chemical structure under specific environmental conditions, resulting in a loss of some properties that may vary as measured by standard methods appropriate to the plastic and the application in a period of time that determines its classification”. This definition can be applied to many polymer degradation types including photodegradation, thermooxidation, hydrolysis and biodegradation. Autooxidation is the cause of thermooxidative degradation of organic materials without light. In natural photodegradation, sunlight reduces the molecular weight of the polymers by photooxidation and direct bond cleavage (Hand Book of Polymer Degradation, 2000). Another mode of degradation is hygrothermal degradation. Substantial loss of weight and mechanical properties of a material due to the effects of moisture and temperature is called hygrothermal degradation (Balakrishnan, Hassan, Imran, & Wahit, 2011). For instance, aged PLA/jute fiber composites in hygrothermal environment showed 15% decrease in tensile strength after 24 h
German Chemist Hans von Pechmann first synthesized Polyethylene by accident in 1898 by heating diazomethane. His colleagues characterized the waxy substance polyethylene due to the fact that they recognized that it consisted of long ethene chains. It was then first industrially synthesized by accident in 1933 by applying extremely high pressure to ethylene and benzaldehyde. Over the years, development of polyethylene has increased due to the additions of catalyst. This makes ethylene polymerization possible at lower temperatures and pressures.1
The traits of a gas in its ideal form are governed by the relationship: PV = n RT (Guch, 2003). A change in either of the values in the relationship results in a change to the other variable of the gas. Assessing the behavior of gases via manipulation of the characteristics is done by holding the factors constant (Zumdahl, 1998). Where the number of gas moles, molar gas constant, and volume of the gas remain constant, a change in the temperature of the gas results to a change in the pressure as well. The ideal relationship between the gas factors is quite complex to be evaluated since it involves holding three of the five factors constant while two factors are assessed. Different gas laws derived from the ideal gas law can be evaluated individually since control can be easier conducted in l...
Contents Abstract Nomenclature 1 Introduction 1.1 Motivation 1.2 Literature review 1.3 NOx formation mechanisms...........................................................................3 1.4 NOx reducing techniques..............................................................................5 1.4.1 Staged combustion..............................................................................5 1.4.2 Partially premixed flames............................................................... 6 1.4.3 Flue gas recirculation.......................................................................8 1.4.4 Catalytic combustion...................................................................11 1.5 Computational fluid dynamic.........................................................................15
Thermal protection is a method of detecting over-temperature conditions and disconnecting the electrical power. This usually used to prevent fires or damage to electronics power supplies and equipment which may arise from the high temperatures.
Binder viscosity was altered by changing temperature. The initial dispersion of the binder in the powder depends upon viscosity and shear rate applied. (Schaefer, 1996) Binder viscosity also controls the consolidation rate and hence subsequent growth via coalescence. (Ennis, et al., 1991). Results from Rough et al (2005) showed that increased temperature (lower viscosity), the regimes are reached faster because the binder is able to distribute more effectively in the mixture at a given shear rate which is in accordance with the work reported by Schaefer et al (1996). As LAS paste quantity was increased, mixing time required to form designated regimes decreased. Work done by Hibare (2012) showed that the peak modal granule diameter stays similar in both reactive and non-reactive high viscous binder systems which was said to be as a result of mixing time. Mort et al (2001) stated that the method of binder introduction/addition could influence the width of an agglomerate size distribution. A smaller binder droplet size can result in narrower size distribution. According to Schongut et al (2013), granule size distributions have a weak dependence on agitation rate (impeller speed) but a stronger dependence on the state of the binder. Schongut et al (2013) presented size distribution results at three different temperatures with the highest temperature having the narrowest size distribution. Research experiment work done by Schongut et al (2013) was carried out in a stirred glass reactor with a sodium carbonate powder bed and the binder (dodecyl-benzenesulphonic acid) injected into the bed. The powder bed was in stoichiometric excess and each powder bed was used for two kinetic experiments before discarded. Using the powder bed twice bef...
Thermal properties of material (Tg, Tm, Td) are those properties that response to temperature. They can be studied by thermal analysis techniques including DSC, TGA, DTA and dielectric thermal analysis. The nanometer-sized of inorganic particles incorporated into the polymer matrix can improve thermal stability by acting as a superior thermal insulator and as a mass transport barrier to the volatile products generated during decomposition [117]. Khanna et al. [57] reported the thermal (TGA) analysis of the PVA/Ag nanocomposite. They observed that the decomposition profile starting at about 330 ◦C and continuing till about 430 ◦C. They also found the PVA/Ag nanocomposites have higher thermal stability than the PVA alone. Mbhele et al. [99] also observed that that the pure PVA starts decomposing at about 280 ◦C and
Figure. 2 gives a brief summary of the applications of biomass-derived degradable polymers. Nowadays, there are tremendous interest in research and using of biopolymers in packaging, civil engineering, biomedical and automotive mystery
By using variable load shell and tube type heat exchanger, controlled heat is transfer between two fluids. It will help to run the pump at constant load and mass flow rate. It will maintain overall efficiency of the pump and save auxiliary power of the whole plant.