what do you mean by "nuclear"?

nucleat sorry

improve crystallization behaviour

I suggest that this is because of the much higher surface area of CNTs, inducing much more interaction per unit weight.

Alain

Thanks , i think so but based on data sheet of GNP , aspectration is much higher than CNTS

it is ~1750 while for CNTS is 157 .

So in these conditions are you sure that the GNPs are not agglomerated in the polymer, thereby leading to a much lower contact area ? If only 10 GNPs are stacked, the surface area will be divided by one order of magnitude, i.e. will be at the level of CNTs. Another possibility is that, because they are so thin, GNPs don't give strong perturbation to the polymer, whereas CNTs are curled and finally induce a much higher disorder.

Alain

not sure mate

Also , why filler accelerate crystalization >

polymer chains interact with the filler surface and get immobilized on the filler surface, this immobilization facilitate and thus accelerate the further nucleation. immobilized surface polymer is also called interfacial polymer.