dear friend Saurabh Gupta

Thank you for raising such an intriguing question about the use of polyethylene’s 100% melting enthalpy as a reference in Differential Scanning Calorimetry (DSC) for assessing the crystallinity of EVA and POEs. I appreciate your curiosity, and I’m glad to explore this topic together.

Polyethylene is often chosen as a standard because its crystalline structure and melting enthalpy are well-characterized, providing a reliable baseline for comparison. By referencing the melting enthalpy of ideally crystalline polyethylene, we can estimate how much of other polymers, like EVA and POEs, are organized into crystalline regions. This method offers the advantage of consistency across studies, but it may also introduce limitations—especially if the polymers being compared have different chemical compositions or crystallization behaviors. Do you see any potential challenges in applying this standard universally?

Crystallization in polymers depends on several factors, such as the regularity of the molecular structure, chain length, and the presence of comonomers or branching. Polyolefins, including polyethylene, often exhibit similar crystalline tendencies due to their structural similarities, making them suitable for comparative analysis. However, even subtle differences in structure can significantly influence crystallinity and, consequently, material properties.

Understanding crystallinity is crucial because it directly impacts mechanical strength, flexibility, and thermal stability—key factors in determining a polymer’s suitability for specific applications. I’d be interested to hear your thoughts on how these insights might inform material selection or product design in your work.

Looking forward to your perspective!

Best regards,

Kaushik

Thanks for your descriptive answer @ Kaushik Shandilya,

I have not studied polymers that much, still I am trying to add in discussion that 'how POEs crystallise' should be elaborated. Is it because hydrocarbon chain alighn parallel to each other or folding of polymer happens? Polyethylene which is a pure hydrocarbon chain of alkane may be a reference for other POEs if POEs hydrocarbon chain (alkane) only take part in crystallisation and other functon groups or branches in polymer are to disturb or don't participate. If it is so, why these alkane chain tends to alighn or folding of polymer happens or why any other way of crystallisation, what are the forces?

Dear friend Saurabh Gupta

Thank you for raising such an intriguing point about polymer crystallization—your observations on polyethylene (PE) provide an excellent foundation for this discussion. As you noted, PE’s ability to crystallize is closely tied to the linearity and simplicity of its hydrocarbon chains, which can align neatly and form ordered, stable structures.

Turning to polyolefin elastomers (POEs), it’s fascinating to consider how their crystallization behavior might parallel that of PE. Since POEs also have predominantly hydrocarbon backbones, it seems reasonable to hypothesize that their chains’ ability to orient and pack efficiently—without significant interference from bulky side groups—plays a central role in their crystallization. The van der Waals forces you mentioned are indeed crucial, as they drive the alignment and stabilization of these crystalline regions. However, I wonder if the preference for alignment over folding is primarily due to the energetic favorability of maximizing these intermolecular interactions, or if other factors, such as chain flexibility or the presence of comonomers, might also influence the outcome.

It would be interesting to explore how even subtle differences in chain structure or the introduction of other elements/groups could disrupt or modify the crystallization process in POEs. Do you think these variations could lead to significant differences in crystallization pathways compared to PE, or are the underlying forces largely the same across different hydrocarbon-based polymers?

I’d love to hear your thoughts on these aspects, especially regarding how specific structural features might alter the balance between order and disorder in these materials. Looking forward to your insights!

Best regards,

Kaushik

First of all, I would like to express my sincere thanks and appreciation for this thoughtful question, which reflects a deep understanding of polymer thermal analysis.

In DSC analysis, the degree of crystallinity of EVA and POEs is calculated with respect to the melting enthalpy of 100% crystalline polyethylene (~293 J/g) because only the ethylene segments crystallize. The comonomer units (like vinyl acetate or other olefins) remain in the amorphous phase and do not contribute to crystallization. Therefore, polyethylene serves as a standard reference to estimate the actual crystalline fraction formed by ethylene sequences.

Dear Mohamed El Gheith Hemade,

Thanks for getting the idea of the question. I would like to ask why only ethylene segments crystallize? Why don't other segments take part in crystallization? (like It may be the range of forces applied, affecting the structure, that is achieved in the thermal budget of polymers.)

The details have already been given above. I like to add that polyethylene crystallizes by simple orientation of the polymer chains. The presence of vinyl acetate molecule along the chain impedes the crystallization ability of polyethylene. Polyethylene is considered as 100% crystalline and vinyl acetate does not make any crystalline segment. You start with 100% crystallinity with PE to lower crystallinity with EVA. Therefore, polyethylene is considered 100% and comparison is made with that having PE main chain with partial introduction of VAc. To clarify further, you are comparing pure with impure and, therefore, the starting point remains the pure.