Methods for the Experimental Study of the Linear Pyrolysis of Condensed Materials
Original instruments for measuring rates of linear pyrolysis (the stationary one-dimensional propagation of the reaction front in condensed compound thermal decomposition) are described. Kinetic constants of the fast high-temperature decompositions of pol
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Methods for the Experimental Study of the Linear Pyrolysis of Condensed Materials
Abstract Original instruments for measuring rates of linear pyrolysis (the stationary one-dimensional propagation of the reaction front in condensed compound thermal decomposition) are described. Kinetic constants of the fast high-temperature decompositions of polymers and inorganic materials (which cannot be obtained using isothermal kinetic methods) can be calculated from the experimental data provided by them. These instruments were used to study the burning mechanisms of modern solid rocket propellants over wide heating temperature ranges (up to 900 ◦ C) and pressures (100 Pa–3 MPa). An instrument called the “chemical arc” is described for the first time. In the chemical arc, the high-temperature linear pyrolysis of solid propellant components (polymer and oxidizer) occurs in the stationary burning mode under the influence of the flat flame of interaction between the gaseous products of linear pyrolysis.
2.1 Equipment for Studying Linear Pyrolysis on a Hot Plate at Pressures P∞ = 0 . 1 kPa–3 MPa A schematic of the LP-1 installation used to study linear pyrolysis on a hot plate at pressures in the range 0.1 kPa–0.1 MPa is shown in Fig. 2.1. Hot plate 1 is mounted on copper rods 2 fixed on a bulky vinyl plate. The hot plate (heater) should be made of a material (metal or alloy) with a high melting point, such as nichrome, stainless steel or niobium. In some experiments (see Sect. ??), the heater and a sample were separated by a thin layer of mica (5–10 μm) to eliminate the catalytic effect of the heater material on the kinetics of the linear pyrolysis. A Pt/Pt–Rh thermocouple (50 μm in diameter) is spot-welded to the center of the heater (just above the sample). The sample (3) is fixed at the end of a steel cylinder 4 which slides along a guiding Teflon rod 5. The sample is pressed onto the heater by a load 6 which is connected to the steel cylinder (4) by a Capron thread that passes over a pulley fixed onto an axle. During linear pyrolysis, rotation of the pulley causes chopper 7, mounted onto the same axle as the pulley, to rotate. A conical gear with a mirror 10 for measuring low rates of linear pyrolysis is fixed to the other end of the
A.S. Shteinberg, Fast Reactions in Energetic Materials, c Springer-Verlag Berlin Heidelberg 2008
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2 Methods for the Experimental Study of the Linear Pyrolysis of Condensed Materials
Fig. 2.1 Schematic of LP-1 installation: 1, heater; 2, conducting rods; 3, sample; 4, sliding cylinder; 5, guide rod; 6, load; 7, chopper; 8, photodiode; 9, light source; 10, mirror
Pt Pt/Rh
electrical pathway vacuum water
axle. As it rotates together with the axle, chopper 7 modulates a light beam incident on photodiode 8, which is connected to a recorder. In installations utilized in earlier studies [1, 2, 3, 4, 5], linear potentiometers were used as recorders. However the potentiometer sensors were easily damaged because they reacted with the gaseous decomposition products. Under these conditions,
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