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Proactive mitigation of PCTFE-related ignition hazards in oxygen systems: I. Development of a voluntary consensus standard specification to control property variation in finished PCTFE parts
Unannealed PCTFE (polychlorotrifluoroethylene) parts were found to continue to undergo stress relief approximately 1.5 years after moulding. This may explain why older (emulsion polymerised) Kel-F inventories do not exhibit the same degree of dimensional instability as seen in newer (suspension polymerised) Neoflon CTFE inventories. Parts made from partially annealed semifinished rod stock also were found to contain residual internal stress that had been locked into the part. Therefore, while annealing semifinished rod stock can be beneficial, a more effective procedure would be to anneal immediately before (best tolerances) or after final machining (best dimensional stability). The present data do not indicate that the fourfold goal of dimensional stability, crystallinity control, high molecular weight, and minimal shift in valve regulator droop and creep can be satisfied simultaneously. Future studies examining the effect of resin grade, process route, annealing and machining history on droop and creep properties should be performed on seats that have been annealed immediately before or after final machining. Findings unique to this study are: (1) M300P (pellets) was more fully annealed than M400H (coarse granular powder); (2) crystallisation of the M400P (abstractor's note: probably M400H) resin is suppressed relative to the M300P resin; and (3) the crystallinity of rod and seats increased in the order: unannealed <150 deg C fast-quenched <175 deg C slow-quenched. Findings consistent with earlier observations include: (1) TMA (thermomechanical analysis) data were more dispersed for seats than for precursor rod stock; (2) valves seats made from compression-moulded rod stock tended to be more crystalline than ones made from extruded stock; (3) machining can influence dimensional stability more than resin grade, moulder, or process route; and (4) depending on process route, crystallinity can vary widely, even when only one lot of PCTFE is used.
Proactive mitigation of PCTFE-related ignition hazards in oxygen systems: I. Development of a voluntary consensus standard specification to control property variation in finished PCTFE parts
Unannealed PCTFE (polychlorotrifluoroethylene) parts were found to continue to undergo stress relief approximately 1.5 years after moulding. This may explain why older (emulsion polymerised) Kel-F inventories do not exhibit the same degree of dimensional instability as seen in newer (suspension polymerised) Neoflon CTFE inventories. Parts made from partially annealed semifinished rod stock also were found to contain residual internal stress that had been locked into the part. Therefore, while annealing semifinished rod stock can be beneficial, a more effective procedure would be to anneal immediately before (best tolerances) or after final machining (best dimensional stability). The present data do not indicate that the fourfold goal of dimensional stability, crystallinity control, high molecular weight, and minimal shift in valve regulator droop and creep can be satisfied simultaneously. Future studies examining the effect of resin grade, process route, annealing and machining history on droop and creep properties should be performed on seats that have been annealed immediately before or after final machining. Findings unique to this study are: (1) M300P (pellets) was more fully annealed than M400H (coarse granular powder); (2) crystallisation of the M400P (abstractor's note: probably M400H) resin is suppressed relative to the M300P resin; and (3) the crystallinity of rod and seats increased in the order: unannealed <150 deg C fast-quenched <175 deg C slow-quenched. Findings consistent with earlier observations include: (1) TMA (thermomechanical analysis) data were more dispersed for seats than for precursor rod stock; (2) valves seats made from compression-moulded rod stock tended to be more crystalline than ones made from extruded stock; (3) machining can influence dimensional stability more than resin grade, moulder, or process route; and (4) depending on process route, crystallinity can vary widely, even when only one lot of PCTFE is used.
Proactive mitigation of PCTFE-related ignition hazards in oxygen systems: I. Development of a voluntary consensus standard specification to control property variation in finished PCTFE parts
Beeson, Harold D. (author)
2006
15 Seiten, 9 Bilder, 4 Tabellen, 25 Quellen
Conference paper
English
Kunststofffertigprodukt , Polychlortrifluorethylen , Qualitätskontrolle , Brandgefahr , technische Beschreibung , Maßunbeständigkeit , Glühen , Qualitätsüberwachung , Kunststoffhalbzeug , Raumfahrttechnik , Bewertungsmethode , Standardprüfmethode , Einflussfaktor , Betriebsdaten (technische Parameter)
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