I was working on a project where I had to work with isotactic PP (Repsol isplen g3e 002) and extrude different films with different levels of cystallinity without using any nucleating agent. So I decided to to keep 3 different variables i.e. chill roll speed, chill roll temperature and the extruder screw speed while maintaining constant thickness of all the samples. The chill roll temperature were 20°C, 40°C, 60°C, 80°C (produced 16 samples), however upon running DSC tests on the samples I could hardly find any difference in the crystallinities. And I am really confused about what might have cause that. Could anyone help me with this or suggest me some literature where I could find something related to my problem. Thanks!
Could you please identify (i) your method to calculate crystallinity (degree of crystallinity) in DSC and (ii) your goal; improve or reduce the crystallinity? Then I can suggest some things for your problem.
(i) I did the DSC tests and compared the melt enthalpies.
(ii) Goal is to improve the crystallinity.
It seems cooling conditions (undercooling and supercooling) in your process did not work because chain ordering process kinetically showed its characteristic behavior (thermal nucleation). Of course it is clearly due to the lack of heteroneous nucletion (athermal) effect created by nuclaeting agents. Without nucleating agent, only way for increasing the crystallinity of polyolefins is thermal annealing. That is a time consuming post-processing route.
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