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lastzealot新虫 (著名写手)
【乱世的奸雄】
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[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
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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
金虫 (著名写手)
- PEPI: 30
- 应助: 49 (小学生)
- 金币: 1367.9
- 散金: 605
- 红花: 95
- 帖子: 1650
- 在线: 520.5小时
- 虫号: 924145
- 注册: 2009-12-09
- 性别: MM
- 专业: 高分子物理与高分子物理化
【答案】应助回帖
★ ★ ★ ★ ★
感谢参与，应助指数 +1
zznjut(金币+5, PEPI+1): I am pleased to advise that you will be granted with a PEPI! Another thing I have to say is that which is the most possible reason?How to rule out other factors? 2012-02-06 18:36:34
感谢参与，应助指数 +1
zznjut(金币+5, PEPI+1): I am pleased to advise that you will be granted with a PEPI! Another thing I have to say is that which is the most possible reason?How to rule out other factors? 2012-02-06 18:36:34
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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 |
8楼2012-02-06 18:18:56
touchhappy
金虫 (著名写手)
- PEPI: 30
- 应助: 49 (小学生)
- 金币: 1367.9
- 散金: 605
- 红花: 95
- 帖子: 1650
- 在线: 520.5小时
- 虫号: 924145
- 注册: 2009-12-09
- 性别: MM
- 专业: 高分子物理与高分子物理化
【答案】应助回帖
★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★ ★
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
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
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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~~ |
9楼2012-02-07 12:58:14