New nucleating agents for shear-induced crystallization of polypropylene
Bibliographic record
Abstract
The effect of shear on the flow-induced crystallization of a polypropylene with and without nucleating agents was studied using shear rheometry. Generally, an increase in strain and strain rate or decrease in temperature is found to decrease the thermodynamic barrier for crystal formation, thus enhancing crystallization kinetics at temperatures between the melting and crystallization points. Second, the use of nucleating agents dramatically increases the crystallization and melting point of polypropylene, thus enhancing the kinetics of crystallization. Herein, we report the quiescent isothermal and shear-induced crystallization (rheology) behavior of a random copolymer polypropylene with ethylene as a co-monomer containing sorbitol nucleating agents (NA) with different degrees of polarity. The presence of sorbitol NA increases the Tm and Tc by 5 °C and 15 °C, respectively. By performing steady-shear experiments at shear rates varying from 0.001 s−1 to 1 s−1, “quiescent crystallization” and “shear-induced crystallization” regions could be identified. From both isothermal and shear-induced crystallization experiments, sorbitol-based NA with the lowest degree of polarity was found to cause the highest crystallization kinetics.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 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".