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lastzealot

新虫 (著名写手)

【乱世的奸雄】

[求助] 请问大虾们在做DSC表征聚合物晶体时有没有见过熔融双峰的情况

最近做了几次PCL及共混物的结晶动力学,发现如果升温较慢,熔融峰会分裂成为两个,不知道这两个峰各代表什么?为什么会分裂?
请各位高手指教啊。
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touchhappy

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【答案】应助回帖

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感谢参与,应助指数 +1
wgs8136(金币+3): 一个帖子中同一虫友的多个有效回复原则上不许重复评定,望谅解,辛苦啦~~ 2012-02-07 13:14:07
wgs8136: 具体可查看http://emuch.net/bbs/viewthread.php?tid=3098426 2012-02-07 13:14:27
zznjut(金币+10): You are a star, although I could not grant you a PEPI. Thank you for your contribution! 2012-02-08 11:45:01
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~~
吃货萌萌哒!!
9楼2012-02-07 12:58:14
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lixuke2005

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wgs8136(金币+1): 欢迎常来~ 2012-02-06 08:43:47
共混要是有两种结晶性聚合物的话,会很容易出现在升温过程中两峰,快的话,两个连在一起了
bla
2楼2012-02-06 03:27:32
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davai

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wgs8136(金币+1): 欢迎常来~ 2012-02-06 08:43:53
结晶的形态不一样也会这样的,有的是结晶密度比较高,有的结晶密度比较低。这与你结晶时的冷却有管,看看高分子物理里面关于晶体的内容就知道了。你还可以用化学腐蚀来区分结晶的
3楼2012-02-06 07:44:09
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zjucandle

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zznjut(金币+4): 欢迎交流,有价值 2012-02-06 08:58:17
lz的熔融峰之前是不是还有冷结晶峰?聚合物本身和冷结晶所生成的晶体两者的熔点可能会出现小的偏移,所以也会出现熔融峰分裂。
4楼2012-02-06 08:49:42
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