Orbital transfer vehicle oxygen turbopump technology. Volume 2: Nitrogen and ambient oxygen testing

The testing of a rocket engine oxygen turbopump using high pressure ambient temperature nitrogen and oxygen as the turbine drive gas in separate test series is discussed. The pumped fluid was liquid nitrogen or liquid oxygen. The turbopump (TPA) is designed to operate with 400 F oxygen turbine drive gas which will be demonstrated in a subsequent test series. Following bearing tests, the TPA was finish machined (impeller blading and inlet/outlet ports). Testing started on 15 February 1989 and was successfully concluded on 21 March 1989. Testing started using nitrogen to reduce the ignition hazard during initial TPA checkout. The Hydrostatic Bearing System requires a Bearing Pressurization System. Initial testing used a separate bearing supply to prevent a rubbing start. Two test series were successfully completed with the bearing assist supplied only by the pump second stage output which entailed a rubbing start until pump pressure builds up. The final test series used ambient oxygen drive and no external bearing assist. Total operating time was 2268 seconds. There were 14 starts without bearing assist and operating speeds up to 80,000 rpm were logged. Teardown examination showed some smearing of silverplated bearing surfaces but no exposure of the underlying monel material. There was no evidence of melting or oxidation due to the oxygen exposure. The articulating, self-centering hydrostatic bearing exhibited no bearing load or stability problems. The only anomaly was higher than predicted flow losses which were attributed to a faulty ring seal. The TPA will be refurbished prior to the 400 F oxygen test series but its condition is acceptable, as is, for continued operating. This was a highly successful test program

Surfactantes reativos não-iônicos em polimerização em emulsão de látices de acetato de vinila - vinil neodecanoato: influência nas propriedades de barreira à água Nonionic reactive surfactants in emulsion polymerization of vinyl acetate - vinyl neodecanoate latexes: influence on the water barrier properties

A indústria de tintas é grande consumidora de látex obtido por polimerização em emulsão. Os surfactantes, essenciais à estabilidade do látex, exercem papel fundamental na produção e na aplicação destes polímeros. Contudo, podem também produzir efeitos adversos nas propriedades do produto, em razão de sua adsorção física às partículas de polímero. Os surfactantes não ligados podem migrar através do filme para as interfaces, formando agregados que podem aumentar a sensibilidade à água, afetando desta forma as propriedades de barreira. Um caminho promissor para minimizar este efeito dos surfactantes convencionais tem sido o uso de surfactantes polimerizáveis, ou reativos, que estão covalentemente ligados ao polímero e, desta forma, não podem ser dessorvidos e migrarem durante a formação do filme. Neste trabalho foram preparados látices de acetato de vinila - vinil neodecanoato (VeoVa 10®), estabilizados com surfactantes não-iônicos convencionais e reativos, e avaliado o desempenho dos filmes obtidos a partir destes látices. Os resultados demonstraram que o uso de surfactantes não-iônicos polimerizáveis pode, sob determinadas condições, trazer ganhos para as propriedades de barreira.<br>The paint industry is a huge consumer of latex from emulsion polymerization. The surfactants, essential to the stability of the latex, play a crucial role in the production and application of emulsion polymers. However, they can also have adverse effects on product properties due to their physical adsorption on the polymer particles. The unbound surfactants can migrate through the film toward the interfaces forming aggregates which increase water sensitivity of the film, thus affecting its barrier properties. A promising way to reduce the negative effects of the conventional surfactants is to use polymerizable or reactive surfactants (surfmers) that are covalently linked to the polymer, which avoids its desorption and migration during the film formation. In this work vinyl acetate - vinyl neodecanoate (VeoVa 10®) latexes, stabilized with conventional and reactive nonionic surfactant, were prepared and the performance of these films was evaluated. It was noted that latexes stabilized with nonionic polymerizable surfactants can bring, under certain conditions, better barrier properties