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Application of olygoesters in the modification of burning layer of ni-trocellulose-based powder

Grzegorz Gąbka

Abstract

Nitrocellulose-based powders are currently the most common propellant material. However, powders produced in classical process composed of mixing nitrocellulose dough, extrusion and drying often do not possess favorable ballistic properties. Modern propellants should exhibit progressive burning behavior, which provides optimal utilization of the energy of gases in a barrel, without exceeding safe level of maximum pressure. One way to obtain desired effect is to introduce deterrents, which slow the burning kinetics of the surface layer of the nitrocellulose powder. During research a optimization of the process of introducing liquid olygoesters into the burning layer from water slurry was made. Conducted experiments allowed the production of powder exhibiting progressive burning up to the p/pmax value of 0.6, with heat of combustion of 3600 J/g. Through the use of sodium chloride as emulsion destabilizing agent the yield of process conducted from water slurry was increased from 40% to 90%. A new method of introducing diisocyanates into powder grains from methylene dichloride which produced solid polyurethane surface layer was elaborated. By combining the processes of olygoester and diisocyanate introduction it was possible to obtain powder with strongly defined progressive burning behavior as well as low hygroscopicity and low surface friction coefficient. The possibility of increasing the energy of obtained powders by addition of nitroglycerin before olygoester introduction was tested. In this way progressive burning powder with heat of combustion of more than 3700 J/g was prepared. The method previously developed for liquid olygoesters of domestic production was successfully adapted for introducing polycaprolactone into the burning layer – which yielded similar results. Secondary subject of the research was studying the kinetics of thermal decomposition of nitrocellulose powders and nitrocellulose. It has been proven that all tested powders are less thermally-stable than pure nitrocellulose and their stability increases with the decrease of grain diameters. Moreover the internal structure study of powder grains is presented in this thesis, based on the obtained plots of dlnα/dt versus 1/T. It is indicated that the kinetics of thermal decomposition follow zero-order model with the division into two steps. This two-step division is not present for pure nitrocellulose and powders which underwent different processes of internal structure unification. It has been hypothesized, that the first step corresponds to the decomposition of porous domains, which exhibit low stability. Conducted experiments did not reveal any direct relation between amount and type of introduced modifier and characteristics of thermal decomposition kinetics.
Record ID
WUT8b06afd3b65a4de3a4ce897ae2ac2b69
Diploma type
Master of Science
Author
Grzegorz Gąbka Grzegorz Gąbka,, Undefined Affiliation
Title in Polish
Zastosowanie oligomerów estrowych do modyfikacji warstwy palnej prochów
Supervisor
Andrzej Książczak (FC/DH-EM) Andrzej Książczak,, Department Of High-Energetic Materials (FC/DH-EM)Faculty of Chemistry (FC)
Certifying unit
Faculty of Chemistry (FC)
Affiliation unit
Department Of High-Energetic Materials (FC/DH-EM)
Study subject / specialization
, Technologia Chemiczna
Language
(pl) Polish
Status
Finished
Defense Date
29-06-2012
Issue date (year)
2012
Keywords in Polish
-
Keywords in English
-
Abstract in Polish
urn:pw-repo:WUT8b06afd3b65a4de3a4ce897ae2ac2b69