You can check some polymer handbooks. If not available, heat the polymers slightly above melting temperature. Hold for 30 min. and then cool very slowly. It is expected that you will get near 100% crystalline polymer. Alternatively extrapolation using flory equation can be done ( TA276, “Determination of Polymer Crystal Molecular Weight Distribution by DSC”, TA Instruments, New Castle, DE ). You can check the table ( B. Wunderlich, Thermal Analysis, Academic Press, 1990, pp. 417-431.) The crystallinity can be determined by XRD, density measurement along with DSC.

Dear Professor Asit Baran Samui,

Thank you so much for your answer.

However, I wanted to calculate the crystallinity of PP/PVB blends.

I don't know how?

May be your valuable answer will clear my concept.

I am waiting your answer.

Dear Mohammad,

in many books you will find for isotactic PP a value of 207 J/g.

Due to my knowledge PVB (Polyvinylbutyral) is amorphous with a glasspoint of about 347 Kelvin. In many appication PVB will be plasticized witzh lower glasspoints.

( A.K. Dhaliwal, J.N. Hay, The characterization of polyvinyl butyral by thermal analysis, Thermochimica Acta 391 (2002) 245–255)

KR Rodion

I agree with Rodion. Considering PVB amorphous, the crystallinity of the blend in any composition will be contributed by PP only. PP has crystallization enthalpy of 207J/g. For any composition the contribution is from PP only. Try calculating the % crystallinity. See whether the values are logically correct. The difference will be there as the presence PVB will definitely influence the crystallization of PP.

Thank you @ Rodion and Asit for your nice solution.

Now my concept is clear and I could calculate the crystillinity% of blended PP/PVB polymer.

The melting enthalpy of my PP/PVB 90/10% blend is 63.75 J/g so the crystallinity is about 31%.

Dear Asit Baran Samui and Rodion Kopitzky I wanted to share with you the another problem regarding this matter.

For Example I have tested 60/40% PP/PVB blended polymer and got the melting enthalpy from DSC -38.66 J/g.

For calculating crystallinity% can I use this enthalpy?

Or is it required to change the DSC value? Because DSC calculate the enthalpy J/g for 100% sample where 60% PP and 40% PVB is present but for melting, only PP is responsible.

So, I wanted to know that can I use the melting enthalpy value directly from DSC? or I have to change it for different percentage of PP.

Dear Mohammad,

Due to the literature value of 207 J/g for PP you can calculate (better approximate) the crystallinity of your PP Phase to: 38,7 / (207 x 0,6) = 31 % .

Don´t use to many decimals in the evaluation of DSC curves. Due to the unknown "real baseline" the accurancy of your measurement won´t be mre accurant than 0,5-1 J/g. (So 38 / (207 x 0,6) = 31 % is also correkt). Please keep in mind that determination of crystallinity by x-ray or IR-techniques will give results in the same range but not the same "numbers".

You can compare your results if you have measured a series of PP/PVB blends , saying that trial XXX has more crystallinity than trial YYY but you can not compare your measurements with third party measurements when the "numbers" are not really different. (due to accurancy of DSC measurment and evaluation).

KR Rodion

DEar Mohammad,

once more, can you send m e a picture of your DAS-curves ( first heating cooling secaon heating). If you have a netzsch or a perkin DSC you can send me the file.

KR Rodion

Dear Rodion Kopitzky thank you so much for your prompt response with good explanations.

Following you I have calculated the crystallinity of a set of variables of PP/PVB blends but my results is not regular (please find the attachment). I con't draw any conclusion of my results.

Why the crystallinity of PP/PVB blends is fluctuating in a irregular manner? Is there any reason behind or it's a mistake in my experiments or calculations?

Dear Mohammad,

your calculation are okay. Crystallinity is not a fixed value. You have a blend in different compositions. The "morphology" of a blend will influence the crystallinity. Without information to the morphology you can´t say not really more to your results. If you are sure that your measured data is okay ( and I will say that you can not make much mistakes in DSC measurements if your DSC is calibrated) "you " have to interpretate the data ( at best in the light of other informations like morphology / IR-spectra....). From my experience the measured data is correct to +- 2 J/g (Basrline variations!!). That will limit the accurancy of crystallinity to 1 % . Adding mistakes in weight the overalll mistake should not be greater than 1,5 %.

A "may be" interpretation: It seems that putting some PVB to PP enhance the crystallinity ( PP will be the continous phase with PVB droplets in it; these droplets may acting as nucleating agents, so crystallinity is greater then in pure PP!) At mixing ratios in the near of one it is possible that you will have so called co-continous phases. Perhaps crystallinity is then reduced, but I don´t know. At higher PVB contents you will have PVB as the continous phase with droplets of PP in it, which then behaves like a pure PP (from DSC data), so you have the same crystallinity for 10/90 and for 100/0 .

From your send data: I suppose that you have different heating rates in your DSC curves and you used the cooling curve for your calculations? Normally you use also the second heating curve after contolled cooling of the sample.

Don´t use the first heating curve, because you will measure all the aging effects also unless you will see the aging effects on crystallinity.

It will be nice if you recommend me (button).

KR Rodion

I agree with Rodion. You have calculated almost correctly. Second run and same heating rate in all the samples are to be followed for analysis. It is very much important that crystallinity is very much affected by the presence of second component. It decreases normally. However, with induces effect from second one it may increase too.

Hi i strongly agree with Asit Baran Samui

Can anybody inform me the melting enthalpy of 100% crystallized Low density polyethylene (LDPE)?

Can anyone suggest me, how to find out melting enthalpy of 100% crystalline of a polymer

Supriya Shetty

The melting nethalpy of 100% crystalline polymers it commonly measured with DCS. The following link provides a summary of 44 heats of fusion for 100 % crystalline polymers. http://www.tainstruments.com/pdf/literature/TN048.pdf

References like the CRC Handbook for Physical and Chemical Properties should have also nice summary tables. These are found in just about all chemistry departments and libraries.

John Reye Sir, so can we use the values from the pdf link you provided for our crystallinity and research article purposes? is it authentic if i may ask?