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lastzealot新蟲 (著名寫手)
【亂世的奸雄】
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[求助]
請問大蝦們在做DSC表征聚合物晶體時有沒有見過熔融雙峰的情況
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最近做了幾次PCL及共混物的結(jié)晶動力學(xué),發(fā)現(xiàn)如果升溫較慢,熔融峰會分裂成為兩個,不知道這兩個峰各代表什么?為什么會分裂? 請各位高手指教啊。 |
金蟲 (著名寫手)
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the possible origin of the multiple melting endotherms can be summarized as follows: (1) melting, recrystallization, or reorganization and remelting during the heating process, (2) existence of at least two crystal modifications (polymorphism), (3) differences in morphology (such as lamellar thickness, distribution, perfection, or stability), (4) physical aging and/or relaxation of the rigid amorphous fraction, (5) different molecular weight species, and so on |

鐵桿木蟲 (著名寫手)

至尊木蟲 (文壇精英)
至尊木蟲 (職業(yè)作家)
榮譽(yù)版主 (文壇精英)
萬里獨行之江湖散人

木蟲 (著名寫手)
金蟲 (著名寫手)
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To determine whether the origin of the multiple melting behavior is caused by crystal modification, WAXD should be performed under different isothermal crystallization temperatures or non-isothermal scanning rates to observe whether the acquired WAXD patterns are identical. The same diffraction peaks at the same location, which indicates that they have the same crystal structure over a wide range of temperatures and heating rates. A faster scanning rate,in my opinion, however, will not provide sufficient time for the samples to recrystallize; thus, in your experiment, you will observe the fact that the number and degree of perfection of the recrystallized materials diminishes, leading to an increase in the area ratio and decrease in the magnitude of the exothermic peak. These results could directly prove that only part of the crystals that correspond to low-thermal endotherm melted and recrystallized during the heating run. To check whether the multiple melting behavior is caused by morphology, SAXS will be used to determine whether the lamellar thickness has been changed. And others possible factors can be separately confirmed by means such as fractionation, relaxation operation and so on. To sum up: I prefer empolying the melting-recrystallization-remelting model to interpret your results in this special case. Best wishes~~ |

新蟲 (著名寫手)
【亂世的奸雄】
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