Engineering topics

Kratzer, R. H.

Publications and source records attributed to Kratzer, R. H..

22 records · Page 2

NASA NTRS1975

Syntheses and degradations of fluorinated heterocyclics

The relative stability of two ring systems, the triazine rings and 1,2,4-oxadiazoles, which offer potential crosslinks useful for curing perfluoroalkyl ether elastomers, has been investigated. Tris (perfluoro-n-heptyl)-s-triazine, the perfluoroether substituted-s-triazine, 1,4-bis/(5-perfluoro-n-heptyl)-1,2,4-oxadiazolyl/benzene, its perfluoroalkyl ether substituted analog, and 3,5-bis-(perfluoro-n-heptyl)-1,2,4-oxadiazole were synthesized and subjected to thermal and oxidative degradation at 235 and 325 C and to hydrolytic degradation at 235 C. The perfluoroalkyl ether substituted triazine and 3,5-bis(perfluoro-n-heptyl)-1,2,4-oxadiazole were found to be stable under all conditions investigated.

Paciorek, K. L.↗

NASA NTRS1974

Crosslinking and degradation mechanisms in model sealant candidates

Heterocyclic ring systems were investigated, triazines and 1,2,4-oxadiazoles. Only a limited effort was extended to the preparation of triazoles. Compounds, n-perfluoroheptyl-s-triazine, a perfluoroether substituted triazine, C3F7OCF(CF3)CF2OCF(CF3) 3C3N3,1,4-bus (5-perfluoro-n-heptyl)-1,2,4-oxadiazolyl -benzene, its perfluoroalkylether substituded analogue, and 3,5-bis(perfluoro-n-heptyl)-1,2,4-oxadiazole were synthesized and characterized. To eliminate the effect due to a tertiary fluorine present in branched materials, the pure n-alkyl-compounds were prepared. The main starting material, perfluoro-n-octanonitrile, was obtained from commercially available perfluoro-n-octanoic acid via a three step synthesis.

Paciorek, K. L.↗

NASA NTRS1973

Flame retardant polyphosphazenes

Six polyphosphazene compositions were prepared by reaction of three bis-tertiary phosphines with two phenyl-s-triazine derived diazides. All six polyphosphazenes produced were completely characterized, four of them were furthermore subjected to isothermal gravimetric analysis, smoke density measurements, flammability and oxidative thermal degradation testing. The results of the characterization studies indicate that only low molecular weight oligomers, possibly of a cyclic structure, were obtained in the polymerization reactions. Despite this, however, two of the materials showed no weight loss after 96 hr at 200 C, one did not autoignite at 500 C in air, and all four self extinguished when exposed to a flame as soon as contact between flame and resin was lost. The only toxic decomposition products to be concerned about were found to be hydrogen cyanide and benzene. Under the conditions employed it was proven, however, that the quantities of toxic products are greatly reduced if no ignition takes place, e.g., if thermal decomposition proceeds at a sufficiently low rate.

Paciorek, K. L.↗

NASA NTRS1971

Fundamental ignition study for material fire safety improvement, part 2

The autoignition behavior of polymeric compositions in oxidizing media was investigated as well as the nature and relative concentration of the volatiles produced during oxidative decomposition culminating in combustion. The materials investigated were Teflon, Fluorel KF-2140 raw gum and its compounded versions Refset and Ladicote, 45B3 intumenscent paint, and Ames isocyanurate foam. The majority of the tests were conducted using a stagnation burner arrangement which provided a laminar gas flow and allowed the sample block and gas temperatures to be varied independently. The oxidizing atmospheres were essentially air and oxygen, although in the case of the Fluorel family of materials, due to partial blockage of the gas inlet system, some tests were performed unintentionally in enriched air (not oxygen). The 45B3 paint was not amenable to sampling in a dynamic system, due to its highly intumescent nature. Consequently, selected experiments were conducted using a sealed tube technique both in air and oxygen media.

Paciorek, K. L.↗