Thermodynamic investigation of the solubility of physical blowing agents in polymer melts
Bibliographic record
Abstract
This thesis is intended to present a theoretical approach based on the thermodynamic models for a thorough understanding on the solubility of physical blowing agents in polymer melts under plastic foam processing conditions. The reliable solubility data of blowing agents in polymer melts are not only useful for the development of next generation blowing agents but also are critical parameters for the optimization of plastic foam fabrication process. As a gravimetric method, the magnetic suspension balance (MSB) was used to measure the sorption of blowing agents in polymer melts under high temperature and pressure. The proposed theoretical approach based on thermodynamic models, i.e., SL-EOS, SS-EOS, and SAFT-EOS, is applied to account for the volume swelling during the sorption and to determine the phase equilibrium or solubility afterwards. The phenomenon about the induced crystallization in PC by the high-pressure CO2 is also studied. The kinetics of high-pressure-gas-induced crystallization in PC was investigated based on the sorption measurements. It was observed that either admitting a higher content of dissolved CO 2 or raising the crystallization temperature could successfully promote the increased mobility of the molecular chains. Consequently, the degree of crystallinity, the melting temperature, and the crystal growth rate were all increased. A comprehensive investigation on solubility was conducted in this study. Various blowing agents (HFC 134a, HFC 152a, CO2, N2, n-Butane) are used in a large number of polymers (linear PP, branched PP, HDPE, LDPE, PS, Engage material, Nylon, polylactide). A novel research methodology is also setup for the investigation on the solubility of gas blends in a polymer melt. It is observed that the linear and branched molecular chain structure exhibits a different behavior in terms of swollen volume and solubility. It is believed that the branched molecular chain structure causes a higher amount of entanglement among the molecular chains which can generate a higher resistance to volume expansion. Therefore, the molecule with branched chain structure generates less accommodation for the small gas molecules to dissolve in the polymer melt and exhibit less swollen volume than molecule with linear chain structure does.
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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".