Engineering topics

Kwong, H.

Publications and source records attributed to Kwong, H..

4 records

NASA NTRS1981

Preparation of crosslinked 1,2,4-oxadiazole polymer

New crosslinked 1,2,4-oxadiazole elastomers were prepared by thermally condensing a monomer having the formula H2N(HON)C-R-Q, wherein Q is a triazine ring-forming group such as nitrile or amidine or a mixture of such group with amidoxime, or a mixture of said monomer with R C(NOH)NH2 sub 2 with R in these formulas standing for a bivalent organic radical. In the monomer charge, the overall proportions of amidoxime groups to triazine ring-forming groups varies depending on the extent of crosslinking desired in the final polymer.

Rosser, R. W.↗

NASA NTRS1981

The 1,2,4-oxadiazole elastomers

Crosslinked 1,2,4-oxadiazole elastomers were prepared either by thermally condensing a monomer having the formula HwN(HON)C-R-Q, wherein Q is a triazine ring forming group such as nitrile or amidine, or by a mixture of said monomer with RC(NOH)NH22, with R in these formulas standing for a bivalent organic radical containing fluorine, hydrogen, or trifluoromethyl. In the monomer charge, the overall proportions of amidoxime groups to triazine ring forming groups varies depending on the extent of crosslinking desired in the final polymer. The heat and chemical resistant elastomers disclosed can serve, for instance, as adhesives, caulking compounds, channel sealants, fuel tank liners.

Rosser, R. W.↗

NASA NTRS1980

Heat- and chemical-resistant oxdiazole elastomers

Heat and chemical resistant polymers with triazine crosslinks are prepared by thermal condensation reactions to form 1,2,4-oxdiazole linkages. They are compounded with variety of fillers, extenders, and modifiers for numerous applications in which stability, impermiability to liquids and gases, good plasticity, and elasticity or rigidity are important.

Rosser, R. W.↗

NASA NTRS1979

Synthesis of perfluoroalkylether oxadiazole elastomers

A method for the simultaneous chain extension and crosslinking of perfluoroalkylethers which yields a thermally stable perfluoroalkylether oxadiazole elastomer crosslinked by trifunctional perfluoroalkylether-1,3,5-triazine is reported. In the preparation, hydroxylamine crystals prepared from hydroxylamine hydrochloride to which sodium butoxide had been added is mixed with perfluoroalkylether dinitrile to obtain the monomer, as the nitrile is converted to amidoxime. Monomers are heated at 140 to 200 C to form poly(perfluoroalkylether oxadiazole) with a 1,2,4-oxadiazole structure by a step-growth polymerization reaction. Simultaneous chain extension and crosslinking are observed to occur when the purified monomer is heated directly and when the remaining nitrile in the monomer is allowed to react with excess ammonia to form the corresponding amidine, which is then heated. Weight loss studies show the thermal stability of the perfluoroalkylether elastomer to be generally better than fluorosilicone or polyester elastomers, especially in air, indicating its potential usefulness for high-performance elastomeric applications.

Rosser, R. W.↗