My project is to put PU foam in the oven at 70C, 80C, 85C, 90C, 100C, 110 and measure the changes in density with an electro densimeter MD 300S. (estimating results are decreasing density with the temperature increase. But the results seem very strange; the density increase and decrease back and forth along 70C to 110C). My question here is
1) Is it true that PU density decreases with increasing temperature?
2) How do I measure/ use electro densimeter MD 300S to get the right result. (I'm using Archimedes method)
(I have a presentation about this tmr and I really need the answer as soon as possible, thanks! )
Hello Casey;
Do you know what is the temperature of melting or temperature that your foam will start go in plastic deformation at? I am asking this because it sounds like when temperature increase, the foam could loose mass due to melting/plastic deformation, etc.. or it could go under complex chemical reaction that we don't know what. But I am not sure why density of foam rises and then drops , ?? Also, remember when you put foam samples in an oven for example at 80 deg C, you have to be sure that you get to steady state temperature for the whole sample; otherwise it will give you different values for density. Maybe you need to send some more details about your test procedure and how much difference in density you see, 5%? 20%, etc. I hope this is helpful!
Best Regards,
Mohamed,
Dear all,
PU foams may exist in different morphologies with regard to the cells structure (open, closed, and dimension scale). Assuming a closed cell case, I think the decrease in density with increasing temperature is due to the expansion of the cell dimensions caused by the dilatation of the gas inside it under the action of temperature. And if the density increases, I think you have a kind of cell collapse caused by the gas leakage from it. I join Dr. Mohammed for the need of an additional details. Regards
A possible reason for the observed behaviour of the obtained experimental data comes from experimental error. Carefully consider and try to reduce or eliminate any possible source of experimental error. Before any meaningful discussion of the data can be attempted it seems necessary to check the accuracy of the obtained data trough statistical error analysis. For the control sample ─ not heat treated ─ and for the samples heat treated at different temperatures, it would be advisable to repeat essays. Possibly you may have to repeat each essay from 3 to 5 times with different samples heat treated at the same temperature. If the (seemingly) wavy behaviour of the experimental data persists, more temperatures must be selected.
@ Mohamed F Alzoubi, @ Abdelkader BOUAZIZ >> Thank you for the answers. Can I get a title of thesis which I can refer?
@ Carlos Araújo Queiroz >> Yes, I think I made experimental error in it. Can you please help me with some thesis about the PU properties relating wth temperature increasing? I was finding online and still hasn't got the solid one. Thank you.
http://web.mit.edu/cortiz/www/Jerry/TPU_final.pdf
This a recent thesis and somewhat has some useful information about Polyurethanes
http://dspace.mit.edu/bitstream/handle/1721.1/15174/14867833.pdf?sequence=1
This is an old thesis but has a lot of good information about Thermal degradation of Polyurethanes, page 21
Also, I attached for you a paper; this paper talks about the subject somewhat and it has some of the effect of temperature on compression stress-strain curves of polyurethanes; on page 7.
Finally, this subject is very interesting and very challenging, but I agree with colleagues above, you should isolate all errors effects on experiments, and you might have to look for ASTM standards for testing polyurethanes! Best luck, Mohamed,
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