關于哪些原因會導致樹脂結晶

longjiang23

Crystallization of Liquid Epoxy Resins
Crystallization
Epoxy resins, under certain conditions, can become solid or have a slush like appearance. This
is called crystallization and it is where some component parts of the epoxy resin form a crystal
like structure.
The crystallization of an epoxy is very similar to water freezing in that it goes from a liquid
state to become a solid. And like water once warmed it will revert back to it liquid state without
any change or damage to the properties of the resin. But unlike water which melts at approximately
0°C the melting point of the Epoxy is 50°C.
How to tell if your resin is affected.
The first signs of crystallization are that the resin becomes cloudy, hazy or milky which are
more easily seen in clear resin systems like the Ampreg 21. This opacity is generated by small
crystals free floating in the resin. But as the size of the crystals increases the resin becomes
more like a slush in that the material will still flow but sluggishly. As this crystallization of the
resin increases the slush forms larger lumps.
As the density of the crystallized resin is higher than the material surrounding it sinks to the
bottom of the container, building in thickness until the whole container becomes solid.
Why has this happened?
First, it will not always happen but some things make it more likely to occur.
Viscosity
Lower viscosity systems are more likely to crystallize as the material can flow into the matrix
patterns required for crystallization.
Purity
The higher the purity of the resin increases the possibility as there are less additives to disrupt
the crystalline matrix forming.
Temperature fluctuations
But the main cause of this effect is repeated changes in temperature; the resin being warmed
and cooled repeatedly. The thermal cycling helps to orientate the material into the right chemical
structure for the material to form crystals. But this should be greatly lessened if the material
is stored as directed in the data sheets which normally are between 10°C to 25°C.
The temperature fluctuations that occur between night and day start or enhance the crystal
growth process.
Dust & Contamination
The introduction of dust particles into the resin can accelerate the process as it does give the
crystallisation process a starting point or "seed" from which to start. And once the process is
started it can progress more quickly due to the self organising nature of chemistry.
How to correct the situation
Remember as stated above this process can be reverted with no damage to the resin - just like
melting water, but the temperature involved will be higher.
I this case you will need to heat the resin to a minimum of 50°C and hold it there until it all
completely melts. If any crystals remain, the whole container may become solid again with a
few days. But if the pail/drum is heated to 50°C until ALL of the crystals have melted the resin
will be fine for months if not years if stored correctly.
The point to note is that it is recommended to heat the material for a longer period at 50°C to
ensure complete melting of the crystals and not remove the container too early from the heat.
When heating the crystallised resin the heat will not be transfer quickly and achieving a
consistent bulk resin temperature will take quite some time, possibly even 2-3 days for drums
or IBCs of resin. If the resin is not solid and does flow, it is good practice to mix the material
regularly to ensure even heating.
It is not possible to give an exact time required to completely remove the crystals as it will
depend on the container size, heat source and regularity of mixing but it is better to give the
material longer at 50°C to ensure complete reversal of the resin to it's liquid form. With some
clear resin systems, like the Ampreg 21, it is possible to see when the crystallized material has
melted as the resin will change from cloudy to clear.
Once the material has reverted back to its liquid state it is perfectly suitable for all applications
and should be used as specified in the technical datasheet.
If you have any questions please do not hesitate to contact a member of the Customer or
Technical Support team.

longjiang23

樹脂結晶是一種物理現象，通過熱或者強力攪拌不影響使用。

tongxuewm

這篇文章應該是中國人寫得，翻譯成的e文

新鮮人

還是去找中文的吧

紅紙鳶

我把樓主的英文翻譯出來了，供大家參考：
環氧樹脂結晶
環氧樹脂，在一定條件下，能形成固體或者表面類似泥漿狀。這個狀態就叫做結晶，是樹脂其中一部分形成晶狀結構的過程。
樹脂結晶非常類似于水結冰，由液態變為固態的過程。能像冰一樣加熱后又可以變回原先的液態而不改變其性質。但是不像冰的熔點在約0℃左右，而樹脂的熔點是50℃。
如何判斷樹脂受到影響了呢？
第一個結晶的信號是樹脂變得渾濁、有薄霧、像牛奶狀，在純凈的樹脂里看得更清楚。渾濁是由細小的晶體浮在樹脂表面上形成的。但是當晶體增加，樹脂看起來更像泥漿，可以流動但是比較粘稠。當樹脂中的晶體變成更多的泥漿，會形成結塊。
當結晶的樹脂液面高于周圍的原料時，它會沉到容器的底部，逐漸變厚，最終整個容器內的樹脂變成固體。
這是怎么發生的呢？
首先，這不是經常發生的，但是一些參數使其更可能發生。
粘度
低粘度體系更容易結晶，因為原料能流到結晶基體格局中。
純度
樹脂的純度越高越容易結晶，因為有更少的添加劑干擾結晶基體的形成。
溫度變化
最主要的影響因素還是反復變化的溫度。樹脂重復的加熱和冷卻。加熱有助于原料恢復正常的化學結構從而更有利于結晶。但是如果原料按照數據單指明的儲存條件（一般在10℃~25℃）下儲存會極大地減小這種可能性。
晝夜溫差的波動會加強晶體增長的進度。
灰塵和污染
有灰塵進入樹脂會加速晶體化，因為它提供了結晶所需的起點或者叫做“種子”。一旦開始結晶，由于晶體自身的性質和化學性它會進展的更快。
如何解決這個問題
前面所講這個過程是可逆的，能像冰融化成水一樣，但是溫度需要高一點。
這個過程你需要加熱樹脂最少50℃以上，維持溫度直到全部融化。如果仍有晶體存在，幾天之后整個容器里的原料還會變成固體的。但是如果完全融化后在正確儲存的情況下可以存放數月甚至一年。
要注意的一點是在50℃加熱樹脂的時間長一點，確保晶體完全融化，不要太早地停止加熱。當加熱的時候不要快速轉移，而要得到一個恒定的樹脂主體溫度，這個過程需要的時間長一點，大概是2~3天/IBC桶。如果樹脂不是固態的并可以流動的話，最好加熱的時候有規律的混拌一下。
如果不能根據容器大小給出一個能完全融化晶體的準確時間，加熱并有規律地混拌，最好停留在50℃的時間長一點來確保樹脂完全液體化。一些純凈的樹脂體系，例如Ampreg 21，能看見結晶原料的變化，從渾濁變得澄清。
一旦原料恢復到液態，能有很好的使用效果，可以作為技術指標上的規定。
如果你有任何問題請不要猶豫，直接聯系客戶或技術服務團隊的人員。

weiyuzhu

在冬天樹脂一般都會結晶，除非這個樹脂不是純的樹脂，

越純潔的樹脂越容易結晶

紅紙鳶

結晶原因：
1.低粘度體系更容易結晶
2.樹脂的純度越高越容易結晶
3.溫度反復變化容易結晶
4.灰塵和污染會加速結晶
解決辦法：加熱溫度在50℃以上，直到樹脂全部融化成液態，再儲存于規定的溫度下。

喇嘛布谷

結晶最常發生在BPA型的環氧樹脂里

喇嘛布谷

1、BPA型的環氧樹脂在室溫下屬于過冷液體，雖呈液態，但有天然的結晶化傾向，在較低溫度時，傾向更明顯。
2、環氧樹脂晶體有略微較高的密度，使得晶體緩慢下沉到儲存容器的底部，透明的樹脂開始出現模糊和渾濁。

caesar09

關于樹脂結晶，只要明白晶核的成因即可，晶核分為兩類：均相成核與異相成核。晶核是晶體的生長中心。聚合物結晶的晶核尺寸在高分子鏈方向為7.5~30納米，在側向為0.4~2納米。均相成核是由聚合物因熱漲落形成的結晶中心，異相成核是由于某種高熔點異相體的存在使客體的表面形成結晶中心。均相成核的理論解釋是基于經典熱力學的分析。其基本思想是把成核視為過飽和蒸氣或溶質的凝聚。所以也就可以解釋為什么氣溫越低、樹脂越純凈越容易結晶。非均相成核的理論是在均相成核經典理論的基礎上發展起來的。它能定性地說明在什么條件下外來粒子可以使晶核優先在這里形成，解釋了一些結晶現象。