Investigation of Crystallization Kinetics in Polyhydroxyalkanoates through Hyperthermal Cycles
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Polyhydroxyalkanoates (PHAs) are emerging, promising sustainable biobased, biodegradable polymers with strong potential to replace conventional plastics in packaging, agricultural, cosmetics, and biomedical applications. In this study, we investigate the crystallization behavior of two key PHA types─polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV)─under both isothermal and nonisothermal conditions using controlled hyperthermal cycles. Isothermal analyses were performed following rapid hypercooling at 500 °C/min to isolate crystallization kinetics, effectively minimizing interference from the cooling stage. The isothermal data revealed activation energies of 91 kJ/mol for PHB and 139 kJ/mol for PHBV. Hypercooling cycles were also employed to examine nonisothermal crystallization kinetics at cooling rates up to 500 °C/min, mimicking industrial processing speeds. The nonisothermal analysis of PHB and PHBV showed a pronounced decrease in crystallinity with increasing cooling rates. Specifically, PHB’s crystallinity dropped from 48.6 to 10.9%, while that of PHBV fell from 45.9% to near zero, accompanied by the disappearance of exothermic peaks. The isothermal and nonisothermal crystallization behaviors were analyzed using the commonly used modeling, revealing the limited capability of these models in terms of the prediction of the nonisothermal crystallization kinetics from isothermal crystallization data. This study provides novel insights into the thermally driven crystallization mechanisms of PHAs and underscores their sensitivity to processing conditions─critical knowledge for optimizing manufacturing techniques in sustainable polymer applications.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".