Hello,
Is anybody aware of a correlation between vicat softening point (ASTM D1525) and Tg for polyethylene (preferrable copolymer with vinylacetate)? Any literature or web references on this?
Thanks,
Peter-Paul de Moor.
I have always assumed a correlation between these two variables, but I must admit I have never really thought about it...
First of all Vicat measures thermo-mechanical properties. It does not give you any information about what type of transition is causing the softening. On the other hand, different methods measure different values of Tg. I think the best you can get would be a rough rule of thumb.
Regards, Oliver
One would think that there should be a correlation, but consider two polymers: one amorphous the other crystalline. I think you will agree that Vicat and Tg will be fairly close together for the amorphous resin such as PMMA or PS, but may be as much as 200C apart on a crystalline resin, such as nylon 66.
Regards,
Ernie
Take a TPE-U Taylormade for applications in cold areas, Tg somewhere at-60°C Vicat somewhere at 150-180°C
a very similar TPE-U made for moderate Klimate Tg about -40°C same Vicat
TPE-U specialised for good chemical rsitance: Tg about -10°C Vicat about 10°C higher than the others
And what about materialös with two or three Tg´s?
I Think there is no corelation in the TPE field Tg tells you something about the lower limit of application and Vicat something about the higher limit...
other materials have "only the higher" limit that ones witch have the applications under the glas transition there Tg and Vicat can be close, but they must not..
Michael I am not a bug I am a undocumented feature
The Vicat temperature has not a strict relationship with the Tg. In this example I have taken EVA (eg : Elvax : see :
VA(%) MI Vicat(°C) Tg (°C)(estimated) 0,28 25 42 -63,6 0,28 6 47 -63,6 0,28 3 49 -63,6 0,25 2 53 -67,5 0,18 2,5 64 -76,6 0,18 0,7 68 -76,6 0,15 8 64 -80,5 0,12 2,5 79 -84,4 0,09 7 73 -88,3
The Tg is estimated by my self and it is in relationship with the VA-content.. Probably you can find it if you search yourself. Tg is measured on different ways like DSC, DMA etc...
You will notice that there is a relationship between Vicat and VA%, MI . It seeems even that when the Tg is lower, the Vicat temperature is higher! Strange? No , this polymer is also crystalline. The more VA% , the less crystalline it is, and the softer it will be at higher temperatures.
My table looked not very nice. This is the nice one:
VA(%) MI Vicat(°C) Tg (°C)(estimated) 28 25 42 -63,6 28 6 47 -63,6 28 3 49 -63,6 25 2 53 -67,5 18 2,5 64 -76,6 18 0,7 68 -76,6 15 8 64 -80,5 12 2,5 79 -84,4 9 7 73 -88,3
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