Vliv zbytkové vlhkosti na zpracování a kvalitu polyoxymetylenu.
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Date
2024-06-11
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Abstract
Tato diplomová práce zkoumá vliv obsahu zbytkové vlhkosti přítomné v polyoxymetylenu během procesu vstřikování na zpracování a výslednou kvalitu dílu. Pro tyto účely byly stanoveny 3 stavy navlhnutí a 5 variant vstřikovacích parametrů. Dále byl u všech těchto variant simulován proces stárnutí pro posouzení tohoto vlivu u zestárlých těles. Dohromady bylo tedy vytvořeno 30 variant. Vliv na výslednou kvalitu a vlastnosti plastu byl posuzován podle výsledků zkoušky vrubové houževnatosti, tahové a ohybové zkoušky a analýzy objemového indexu toku taveniny. Z výsledků zkoušek bylo zjištěno, že vliv zbytkové vlhkosti se u nezestárlých těles projevuje jen minimálně, avšak u zestárlých vzorků již docházelo ke značným rozdílům mezi variantami. S vyšším obsahem vlhkosti během procesu vstřikování byl pozorován vyšší pokles vrubové houževnatosti a modulu pružnosti v tahu a ohybu. Zvyšovala se také hodnota objemového indexu toku taveniny. Zároveň s vyšší teplotou teplotního profilu vstřikování a vyšším zpětným tlakem docházelo k ještě větším rozdílům mezi naměřenými hodnotami pro jednotlivé stavy navlhnutí a byl zaznamenán větší pokles vrubové houževnatosti, modulu pružnosti v tahu a ohybu a nárůst hodnot objemového indexu toku taveniny.
This thesis examines the effect of residual moisture content present in polyoxymethylene during the injection molding process on processing and the resulting part quality. For these purposes, 3 moisture levels and 5 variants of injection parameters were established. Additionally, an aging process was simulated for all these variants to assess this effect on aged samples. In total, 30 variants were created. The impact on the final quality and properties of the plastic was assessed based on the results of the notched impact strength test, tensile and bending tests, and the volume melt flow index analysis. The test results showed that the effect of residual moisture is minimal in case of non-aged samples, however, significant differences between the variants were observed in case of aged samples. Higher moisture content during the injection molding process resulted in a greater decrease in notched impact strength and tensile and bending modulus of elasticity. The value of the volume melt flow index also increased. Furthermore, with higher temperature profiles during injection molding and increased back pressure, even greater differences were observed between the measured values for the individual moisture levels, with a more significant decrease in notched impact strength, tensile and bending modulus of elasticity, and an increase in melt flow index values.
This thesis examines the effect of residual moisture content present in polyoxymethylene during the injection molding process on processing and the resulting part quality. For these purposes, 3 moisture levels and 5 variants of injection parameters were established. Additionally, an aging process was simulated for all these variants to assess this effect on aged samples. In total, 30 variants were created. The impact on the final quality and properties of the plastic was assessed based on the results of the notched impact strength test, tensile and bending tests, and the volume melt flow index analysis. The test results showed that the effect of residual moisture is minimal in case of non-aged samples, however, significant differences between the variants were observed in case of aged samples. Higher moisture content during the injection molding process resulted in a greater decrease in notched impact strength and tensile and bending modulus of elasticity. The value of the volume melt flow index also increased. Furthermore, with higher temperature profiles during injection molding and increased back pressure, even greater differences were observed between the measured values for the individual moisture levels, with a more significant decrease in notched impact strength, tensile and bending modulus of elasticity, and an increase in melt flow index values.
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Vstřikování plastů, zbytková vlhkost, polyoxymetylen, degradace, stárnutí plastu, mechanické vlastnosti polyoxymetylenu, objemový index toku taveniny.