Azzul flawen
I am studying the miscibility of amorphous and semi-crystalline polymer blends using differential scanning calorimetery (DSC) to calculate blend crystalinity. the relationship given by Xcry%=(Hm-Hcc)/w/H0 whre the Xxry is the degree of crystallinity, Hm melting point entalpy, w is weight fraction of crystalline polymer. H0 is the enthalpy of melting of 100% crystalline polymer and
Hcc is the enthalpy of cold crystallization??? how I can determine this enthalpy???
Thank you
Hi,
The cold crystallization is a phenomenon showed by some glass formers. When cooling from the melt, these materials can partially or not crystallize but if we heat up the so-formed amorphous materials, the polymer chains will have enough mobility to crystallize during the heating scan (an exothermic peak is present during this scan). Then, the crystals will melt if we heat up above the melting temperature.
For a completely amorphous polymer (before the heating scan), the enthalpy of cc (integration of exothermic peak in J/g) will be equal to the melting enthalpy (integration of endothermic peak in J/g) when the sample is heated up to the molten state in the same heating scan.
If the polymer does not crystallize during the heating but during the cooling scan there's no cc and the degree of crystallinity is equal to Xcry(%)=(Delta Hm)/w(Delta Hm0).
I hope this will be helpful to you
thank you Sir for your explication
I used the poly vinyl alcohol-co-ethylene, the thermograms of PEVAL and their blends showed an only peak endothermic, it was the melting point temperature and no the exothermic peak appeared in the thermograms, when I cooled the blends also one peak was appeared, it was the crystallization temperature.
so, no cold cristallization, but I found two relationship
one it's your relationship and second relathion Xcry=Hcry/H0
what relation I use
cordialement
In your case, EVOH copolymers do not show cold crystallization and the degree of crystallinity is estimated as follows: Xcryst=DeltaHm/DeltaH0m.
You can find more details in the attached file (Figure 5 and Equation 2).
Best regards,
J. SOTO
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