It all depends on what kind of enthalpy you are measuring. But, before you compare, you need to normalize the enthalpy value by deviding the measured value by the polymer content so that 100% polymer equivalent values can be compared. So, the filled polymer shows 100% polymer equivalent enthalpy of 66 J/g, which is still very low when it is compared with the pure polymer. In this case, you need to evaluate the influence of the filler surface on the particular phenomenon you are measuring the enthalpy for. For example, if you are measuring the enthalpy of crystallization, then the filler surface prevented the polymer to crystallize. If you are measuring the heat of polymerization, the filler surface must have catalyst poisoned the polymerizing system.

Dear Mousam,

From your question is not very clear what kind of enthalpy is concerned in your DSC experiment (enthalpy of melting, of crystallization or of cold crystallization), thus it is very difficult to give the best advice. Did you check that your samples have the same thermal history? Some polymers can be crystallized by the industrial supplier, while the polymer matrix of your composite can have much lower crystallinity due to the specific experimental conditions of fabrication/cooling.

I will exclude here the hypothesis that your filler could have eventually some strong role of “anti-nucleating agent”! We don’t know the nature of your polymer, but let’s go to follow some basic pathways in our DSC analysis:

1) Please analyze the neat polymer doing a first DSC heating scan (e.g. at 10°C/min) up to a temperature somewhat bigger than the melting temperature with about 20-30°C, keep at this temperature the polymer in the molten state 2-3 minutes, and then follow the DSC cooling scan( by 10°C/min) up to a temperature of interest (e.g., 0°C, -20°C, etc. / it is your option) to evidence all thermal events. Keep under isothermal conditions about 2 minutes and follow a second DSC heating scan (10°C/min). Do the calculus of enthalpies and evidence the thermal events, to be certain that everything is correct.

2) Repeat the same pathways, but with the polymer composite containing filler. For, more facility it will be required to introduce in your DSC program only the weight of polymer from your sample, like it was proposed by other RG colleagues. (NB: The DSC procedures & speed of scans can be somewhat different function of your polymer, main goal of analysis, etc.)

Compare the two results! It is very important to evaluate the samples with the same thermal history (i.e., DSC results obtained during cooling, or during second DSC heating). Finally, let’s go to hope that we have obtained what is expected!

Good luck and best regards,

Marius

For eventual help:

Article Polylactide compositions. Part 1: Effect of filler content a...

I hope the article given below may help you

https://www.researchgate.net/publication/315713341_'Thermal_analysis_of_ABSPA6_polymer_blend_using_differential_scanning_calorimetry'