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incompatible contaminations; in particular polyolefines diminish the mechanical properties. The polyethylene as a polymer of low glass-transition temperature should be a good impact modifier of PVC but the incompatibility makes its application seemingly
known that physical changes in food powders are related to the glass transition phenomenon. The most important change in the amorphous state occurs over the glass transition temperature ( T g ), which is the temperature at which polymeric materials
constant (≅10 12 Pa s) [ 13 ], it was postulated that a high value of the reduced glass - transition temperature , T rg (= T g /T m ) , would result in a high viscosity in the undercooled liquid state, and, consequently, lead to a low R c . Zanotto
CdS nano-particles at 25 K min −1 heating rate. Similar DSC thermograms have been obtained for each composite at different heating rates (5, 10, 15, and 20 K min −1 ). From these thermograms, the peak glass transition temperature ( T gp ) was
Artificial ageing of double base rocket propellant
Effect on dynamic mechanical properties
Abstract
The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket propellants. In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures, in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties were studied using dynamic mechanical analyser (DMA). The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus, loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass transition and softening temperature, and tanδ at viscoelastic region.
alloy, and for Fe 67 Co 18 B 14 Si 1 , commercial name of which is 2605CO, are studied. Using glass transition temperature ( T g ), the activation energy ( E ), and fragility index ( m ) are determined. The DSC defines the glass transition as a
(ether-sulphone)–poly(etherether-sulphone) (PES–PEES) copolymers, whose chains are more flexible than PES because of the presence of a larger number of ether links, present a good balance between low viscosity, high glass transition temperature ( T g ) and thermal stability. We thus investigated
Thermal characteristics of gelatin extracted from shaari fish skin
Effects of extraction conditions
-melting); b DSC curve for gelatin extracted from shaari skin at 0.01 N concentration and 293 K ( A glass transition, B unfolding, F endothermic peak, S solids-melting); c Onset glass transition temperature as a function of extraction temperature for
-isothermal conditions [ 13 , 14 ]. In the isothermal method, the sample is brought rapidly to a temperature above the glass transition temperature and the heat evolved during the crystallization process at a constant temperature is recorded as a function of time. In
XRD patterns), colorless and transparent samples were obtained. The obtained glasses were annealed for 1 h at temperature near their glass-transition temperature ( T g ). Fig. 1 Synthesized sample of system Ga 2
