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TGA 教學操作講習會. 石燕鳳. Thermogravimetric analysis (TG) is the study of weight changes of a specimen as a function of te-mperature. The technique is useful strictly for transformations involving the absorption or evolution of gases from a specimen consisting of a condensed phase.
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TGA教學操作講習會 石燕鳳
Thermogravimetric analysis (TG) is the study of weight changes of a specimen as a function of te-mperature. The technique is useful strictly for transformations involving the absorption or evolution of gases from a specimen consisting of a condensed phase. Most TG devices are configured for vacuum and/or variable atmospheres. The balances associated with TG’s are highly sens-itive. These instruments may be used for a wide variety of investigations, from the decomposition of clays to high temperature oxygen uptake in the processi-ng of superconducting materials. THERMOGRAVIMETRICANALYSIS (TGA)
熱重量分析儀(Thermogravimetric Analyzer, TGA)是用於量測樣品材料在特定溫度條件下的重量變化情形的儀器。 其主要原理係將樣品置於一個可透過程控式升溫、降溫或恆溫的加熱爐中,通入固定的環境氣體下(例如:氮氣或氧氣), 當溫度上升至樣品中某一材料成分的蒸發溫度、裂解溫度、氧化溫度時,樣品會因為蒸發、裂解、氧化而造成重量的損失, 記錄樣品隨溫度或時間的重量的變化,即可判定材料的裂解溫度、熱穩定性、成分比例、樣品純度、水份含量、還原溫度及材料的抗氧化性等特性。 • 熱重量分析儀(TGA)原理 • Principle of Thermogravimetric Analyzer
TG curves DTA curves
TGA應用實例 1.高敏感性揮發性物質含量分析 圖是保特瓶(用量僅需2.4 mg)之分析結果,顯示其中含有 0.2102%高敏感性揮發性物質。
2.藥物特性測定 可協助藥物學家了解藥物之熱力學參數,如圖是藥物lactose monohydrate之熱裂解分析圖 圖四Lactose monohydrate之熱裂解分析圖
3.分析無機成份含量 由殘留灰份可測定材料中無機成份之含量,圖是PE果汁包裝瓶之分析,顯示其中含有0.28% 無機成份。 圖五PE果汁包裝瓶之無機成份分析
4.阻燃性質分析 藉由熱重分析儀可了解材料的阻燃性,以及阻燃劑之阻燃效果。例如圖六分析結果顯示PE加入阻燃劑後,其熱裂解比例明顯降低。 圖六PE阻燃性質分析
5.熱穩定性分析 圖七是PVC、PMMA、HDPE、PTFE及PI等材料之熱穩定性分析,可看出PI之熱安定性最佳。 圖七材料之熱穩定性分析
6.組成分析 如圖八可分析出三種不同塗料中之組成成分之差異。 圖八 塗料中之組成成分之分析
Flynn and Ozawa have shown that at a constant degree of conversion, α, the activation energy, E, of a reaction is related to the heating rate,β, and the temperature, T, by the following equation: The value of E can be obtained from the slope of the logβ versus 1/T plot.
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