Chemistry Reference
In-Depth Information
Chapter 9
Kinetic of Deep High-Temperature
Decomposition of Model and Commercial
AP-Based Composite Solid Propellants
Abstract
The kinetics of fast high-temperature decomposition is quantitatively stud-
ied for a number of model and commercial heterogeneous polymer-ammonium per-
chlorate systems using original nonisothermal kinetics methods employing DTA,
TGA and DSC instruments. Maximum temperatures corresponding to the deter-
mined kinetic parameters reach 400-450
◦
C, which are quite close to those in the
solid propellant reaction zone near the burning surface. Data presented in this chap-
ter can be used for the analysis of combustion patterns and mechanisms of solid
propellants, while the results of earlier works on the kinetics of low-temperature
decomposition are only useful for assessing the stabilities of the propellants during
long-term storage. This is also confirmed by comparing the corresponding kinetic
constants. For example, the activation energies for the low-temperature decomposi-
tion of the majority of the studied solid propellants are close to 120 kJ mol
−
1
, which
corresponds to the decomposition of AP. The activation energy of the second stage
of the high-temperature decomposition of almost all AP-polymer mixtures is twice
as high. An explanation of this quite general effect is presented. An excellent corre-
lation between the obtained kinetic constants of high-temperature reactions and the
ignition parameters and the rates of subatmospheric burning for the studied solid
propellants is discussed.
9.1 Kinetics of High-Temperature Decomposition
of AP-Polymer Model Systems
The macrokinetics of the high-temperature decomposition of AP-based heteroge-
neous model and commercial mixtures were studied by DTA and TGA methods
using thermal dilution. In most of the experiments, the oxidizer particle size was
d
AP
= 200
m.
Since the fuel-binder content in commercial composite solid propellants is about
20%, the oxidizer/fuel ratio in the model mixtures was 4/1. The following polymer
powders were used as fuels in the model mixtures: polystyrene (PS), polyvinylchlo-
ride (PVC), polyacrylonitrile (PAN) and polyethylene (PE). The particle size of
the powders was not important, since all of these materials melt before active
μ
m, while in other experiments
d
AP
= 50
μ
