Effect of Ethylene Comonomer Content on the Foam Processing Window of Long-Chain Branched Polypropylene
Bibliographic record
Abstract
The non-optimized foam processing window (FPW) can create processing challenges and limit the possible materials with which a polymer of interest can be processed in emerging foaming technologies. To address this drawback, we aim to investigate the effect of ethylene comonomer content on the foaming behavior of polypropylene (PP), particularly the FPW. Two PP resins containing 0.75 and 1.5 wt % of ethylene comonomers were studied, while using a PP homopolymer as a control. High-pressure differential scanning calorimetry confirmed the decrease in the onset crystallization ( T c-onset ) and end melting ( T m-end ) temperatures with increasing ethylene comonomer content as a result of the defects the ethylene units induce in the crystalline structure of PP. Rheological measurements suggest that the addition of ethylene comonomer content resulted in negligible changes in the extensional and shear rheological responses of the PP-based resins. In addition, the foam expansion results and the observed morphologies reveal no significant change in the resins’ foamability, characterized by the shape of their expansion profiles with respect to the foaming temperature. Interestingly, the FPW was found to be the sole affected parameter, as 1.5 wt % of ethylene comonomers resulted in a 10 °C shift in the FPW toward lower temperatures, compared to the PP homopolymer. The resins with 0 and 1.5 wt % of ethylene comonomer content showed similar mechanical responses under compression tests for their optimally expanded samples. These findings reveal a potentially effective approach for tuning the FPW of processed PP resins without compromising their foaming and mechanical performances. Consequently, foam processing techniques are further enhanced, resulting in a wider span of potential applications.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".