It is because plasticizing effect gained from organic surfactant.

Read more about this effect, you will find the answer.

The effect can arise from interactions between the filler and different regions in the polymer matrix, such as tie molecules and truly ammorphous regions. This interaction may increase free volume in the polymer, thus lowering Tg.

Have you noticed a trend in this phenomenon for a series of nanocomposites with increasing ammounts of filler, for instance?

I think this phenomenon is due to the decreasing the degree of crystalization

i need to lnow what ur matrix is

Thanks for your comments

It's polyethylene terphalate

Another option is that the Tg is reduced due to the fact that the sizes of the polymer domains are reduced to small values. It is known that the Tg-s of thin polymer films (nm-range) are also smaller than in thick polymer films of exactly the same polymer.

Thanks for your kind comment

tan delta peaks are higher in the case of acid treated compared with untreated MWCNTs. Any idea please.

How did you derive the Tg? Answer might be related to the method used.

DMTA test.

if ur nano composite is prepared via melt mixing method or solution mixing this could be happend

cnt nano particles deprive PET macro molecules to create crystals

as a matter of fact it reduces the degree of crystalization and Tg

Thanks Holman for your kind addition.

But this behaviour occurred only when acid treated carbon nanotubes added.

Also , yes , degree of crystallization decreased but I think if degree of crystallinity decrease , tg should be increase or does not change at least. ?

Thanks

Did you use G" or tan d peak value? It should be G" as melting is relaxation. tan d peak position could be misleading due to Payne effect,

Best regards,

Gabor

dear Ba

as far as im concerned if the degree of crystalisation is decreased, Tg should be decreased too.

but i have no answer of why this happened when u use acid treated CNT and didnt happened when u used CNT

tHANK FOR ALL OF YOU

ThANK FOR ALL OF YOU

If the Tg not change after adding treated CNTs , what does this means

to me this is quite obvious. The nanofiller produces a lot of interface,  it creates surface and Tg will reflect the Tg of a surface of a polymer which is also lower than bulk Tg. I am very interested in experimental data on nano filled polymers, if you can send me any as I am intending to write a review on Tg (still ill understood or ill interpreted at the fundasmemntal level) [email protected]