John A. Parker

Molecular Configuration and Pyrolysis Reactions of Phenolic-Novolaks

Abstract The mechanism for heat rejection of char-forming, ablative heat shields is well known [1]. However, the data needed by the engineer to design heat shields have often been determined by laboratory experiments [2–4]. The fraction of heat shield which remains as char after pyrolysis and the thermokinetic parameters for thepyrolysis process have been estimated from thermogravimetric measurements [5,6]. This empirical approach to determining the char yield of phenolic heat shields and the fraction of polymer involved in the pyrolysis reactions has been the result of lack of definitive information on the mechanism of high-temperature decomposition of the polymers used in compounding the heat shield.

The Development of Polybenzimidazole Composites as Ablative Heat Shields

Abstract The excellent high-temperature mechanical properties and other desirable characteristics of polybenzimidazole (PBI) polymer systems make these systems attractive candidates for development as ablative heat-shield materials. This paper describes the formulation of several new low-density polybenzimidazole composites. The proposed structure of the basic linear PBI prepolymer and of several highly cross-linked PBI polymers are presented. The cross-linked PBIs were obtained either thermally (by postcuring to a high temperature) or chemically (by the use of either preoxidized polyfunctional amines or triphenyl trimeasate as a comonomer in the polymerization).

A kinetic model for the acid-catalyzed decomposition of Delrin

Abstract A kinetic model is derived for the acid-catalyzed decomposition of Delrin, an acetal-formaldehyde resin. The kinetic model proposed assumes the hydrolysis of Delrin to form polyformaldehyde and the subsequent decomposition of polyformaldehyde to formaldehyde.

Methanator fuel conversion

Abstract A methanator or catalytic steam reformer fueled engine was operated in the laboratory as part of a clean fuel conversion program. Design information for the fuel reformer has been obtained for hydrocarbon fuel conversion to a methane fuel for a nickel catalyst system in the temperature range 250–500°C, in the pressure range 1–4 atm, and up to 1.7 (10 −4 ) g fuel g −1 cat. s. It was found that trace quantities of O 2 and alkali metal doping of the nickel catalyst increase catalyst life and decrease carbon deposition. A comparison of rate data and mass transfer effects for catalyst pellets suggests that fluidized or tubular reactors would be more efficient than pellets in fixed bed reactors. When unleaded gasoline feed is reacted in this system, a liquid product with a higher average boiling point and with a higher aromatic content results. This product should be eliminated to maintain a cleaner burning gaseous fuel.