I am performing cycle testing of a phase change material and I noticed that after a certain number of melt/freeze cycles, this PCM has turned yellow. Can anyone tell em what can be the reason behind it?
Regards
Ravi
Dear Ravi Sharma :
What material is the one you are working with ?
Can you tell the whole structure ?
Regards !
Dear Franklin
It was polyethylene glycol of molecular weight 2000.
Regards
Dear Ravi :
Unfortunately I don't know Polymer Chemistry, but I may have a clue.
In semiconductor Physics when you have a material with Oxygen in it, could be as small concentrations as secondary phases, or maybe in the surface, as an oxidized surface. When the material (or the surface) lose Oxygen, due to a treatment of annealing, or another heat treatment, or another degradation procces, depending on how much Oxygen is gone, a turn in color to a yellowish coloration can be observed.
Do you think what you are observing could be related to this ?
Regards !
Hi Franklin.
Theis might be the reason, though I am not sure because none has reported about this change. Well the linear formula of this material is HO(C2H4O)nH.
Can you guess now?
Regards
Dear Ravi Sharma :
I would n't be able to give you a guess based on this hypothesis and the formula of the polymer, I'm sorry.
But I think the hypothesis is plausible.
I guess you will have to give it a larger research in the literature to see if you can find something about this relationship, also on how much O % is lost after these melt/freeze cycles ,
Can you do a Chemical Analysis to your polymer ? Before and after you see this transition phase. Maybe you can calculate the % loss of Oxygen performing a TGA analysis ...
Regards !
Dear Franklin,
I did TGA after cycle test, and could see some loss in decomposition temperature too. same time loss in latet heat too.
I guess if I club these 2-3 losses and then I may correlate it with oxygen loss.
Though I am not sure.
Let me check with literature.
Thank you very much. You gave me some idea about it.
Regards
ravi
Most PCMs get oxidized after several cycles but its effect seems insignificant to its thermal performances
This question was asked by one of the reviewers of one of my recent papers concerning the nature of erythritol after several cycles.
I carried out an investigation on erythritol and observed that it dose not oxidize.
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