Pyrolysis Gas Composition for a Phenolic Impregnated Carbon Ablator Heatshield

Abstract

Published physical properties of phenolic impregnated carbon ablator (PICA) are compiled, and the composition of the pyrolysis gases that form at high temperatures internal to a heatshield is investigated. A link between the composition of the solid resin, and the composition of the pyrolysis gases created is provided. This link, combined with a detailed investigation into a reacting pyrolysis gas mixture, allows a consistent, and thorough description of many of the physical phenomena occurring in a PICA heatshield, and their implications, to be presented.

Development of Small Scale Arc-jet Facility OPG1

“…The heavily diluted gas passes through a filter outside the building and is released into the atmosphere. The composition of this gas can be estimated using the simulation results from Ref [20] showing that the major species at cooled ambient conditions are CH 4 , CO 2 and CO. Using the approximate results discussed above, the diluted mole fractions at the filter vent to atmosphere are 1.3E-3, 7.7E-4, and 2.6E-5 respectively, all of which are far below dangerous levels.…”

Detailed Modeling of Cork-Phenolic Ablators in Preparation for the Post-flight Analysis of the QARMAN Re-entry CubeSat

“…This is a strong assumption, as the composition of pyrolysis gases actually is a function of the local thermodynamic conditions and elemental composition. Considering that pyrolysis gases flow at relatively low speeds inside the porous medium [36], a very common assumption in the literature is to impose the production of volatile compounds of pyrolysis at thermochemical equilibrium. Therefore, a new routine was implemented within argo, to provide muta-tion++ the local temperature and pressure so that, starting from the elemental composition of pyrolysis gases, muta-tion++ is able to compute m i,I at the local thermochemical equilibrium (Fig.…”

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

“…1,2 Referring to phenolic resins, the controlling factors for high carbon yield are the crosslinking density, the size of the molecules after polymer curing process, the presence of other trace elements such as oxygen or nitrogen left over from curing of novolac resins and the pyrolytic atmosphere (inert or not). [2][3][4][5] Glassy carbon is the pyrolysis product of cured phenolic resins that exhibits excellent properties, namely low specific gravity, high Shore hardness, thermal resistance to pyrolytic temperatures of up to 3000 °C (in non-oxidising atmospheres), high resistance to corrosion by acids or bases, thermochemical resistance up to 550 °C in the presence of air, high electrical conductivity, good gas permeability and biocompatibility. 3,6 The mechanical properties of C/C composites are highly enhanced by the presence of carbon fibres as a reinforcing agent because they combine low weight, high strength and stiffness, dimensional stability, low thermal expansion coefficient, high strength at high temperatures (3000 °C in non-oxidising atmospheres) that increases with increasing temperature, higher thermal conductivity than copper and silver, high thermal shock resistance and low recession in high-pressure ablation conditions, high chemical resistance, biological compatibility and fatigue resistance.…”

“…While novolac resin is produced with a molar excess of phenol to formaldehyde (F/P < 1) in the reaction mixture in the presence of an acidic catalyst, resole resin requires a basic catalyst and a larger molar excess of formaldehyde to phenol (F/P > 1). 4,16,17 As a result, novolac resin is more stable and demonstrates infinite shelf-life because its macromolecules bear edge-phenolic groups. It also requires a crosslinking agent to cure, as opposed to resole resin, whose methylol and dibenzyl ether edge groups are reactive enough to complete the polymerisation (via the formation of intermediate resitole) and cure the resin to resite without the addition of a curing agent.…”

“…Carbon/carbon (C/C) composites usually originate from composite materials of thermoplastic or thermosetting polymeric matrices (pitch, furan and phenolic resins) since these materials give a high carbon yield of 55–70% as pyrolysis residue 1,2 . Referring to phenolic resins, the controlling factors for high carbon yield are the crosslinking density, the size of the molecules after polymer curing process, the presence of other trace elements such as oxygen or nitrogen left over from curing of novolac resins and the pyrolytic atmosphere (inert or not) 2–5 . Glassy carbon is the pyrolysis product of cured phenolic resins that exhibits excellent properties, namely low specific gravity, high Shore hardness, thermal resistance to pyrolytic temperatures of up to 3000 °C (in non‐oxidising atmospheres), high resistance to corrosion by acids or bases, thermochemical resistance up to 550 °C in the presence of air, high electrical conductivity, good gas permeability and biocompatibility 3,6 .…”