### Abstract

A comprehensive thermochemical model for polytetrafluoroethylene (PTFE), also knownas Teflon®, is developed for use with computational fluid dynamic and magnetohydrodynamic computer codes. The model computes the thermodynamic properties of PTFE for a temperature range of 500 K to 580 230 K (50 eV) and extends to density values as low as 10 ^{-8} kg ̇ m ^{-3}. The 23 equation nonlinear system produced under the assumptions of ideal gas and two-temperature local thermodynamic equilibrium (LTE)was solved numerically using the Newton-Raphson method. The extended thermochemical model is verified for both the composition and thermodynamic properties by comparisons to existing thermochemical models in the literature. These comparisons verify themodel for the available, yet limited, temperature and density ranges. The properties display expected trends such as an increase in the degree of ionization with decreasing density, while almost independent of the electron to heavy-particle temperature ratio (θe/h = T _{e}/T _{h}). The specific internal energy adheres to a fairly predictable curve, i.e., the specific internal energy is linear as the mixture stays at a fairly constant composition over some T _{e} range. However, over the T _{e} range where reactions occur, it was observed that such variation shows a steeper positive slope that represents energy deposition to the internal modes of the gas as opposed to heating. That is, the density is the main factor in deviations from one curve to the next while θ had a slight effect. Likewise, for the specific internal energy, the density had the greatest impact.

Original language | English (US) |
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Pages (from-to) | 1918-1941 |

Number of pages | 24 |

Journal | International Journal of Thermophysics |

Volume | 32 |

Issue number | 9 |

DOIs | |

State | Published - Sep 1 2011 |

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### Keywords

- Electric rocket propellant
- Equation of state
- High-temperature thermochemical model
- Polytetrafluoroethylene
- Thermal non-equilibrium

### ASJC Scopus subject areas

- Condensed Matter Physics

### Cite this

*International Journal of Thermophysics*,

*32*(9), 1918-1941. https://doi.org/10.1007/s10765-011-1030-y