Modeling of internal residual stress in linear and branched polyethylene films during cast film extrusion: Towards a prediction of heat-shrinkability
Bibliographic record
Abstract
The singular property of shrinkage is used in the packaging sector to wrap products. Polyethylene film products are mostly produced by either blown or cast film extrusion. During processing, under the effect of drawing, the molten polymer is stretched in one or two dimensions according to the cast or blown film extrusion. When the resulting solid film is subjected to a sudden increase in temperature, it shrinks as a result of the relaxation of polymer chains that were oriented under stress and frozen in a stretched state upon processing resulting in internal residual stresses. A general viscoelastic model in the framework of large strain has been used to predict the development of the internal residual stresses stored during the stretching stage of the process. Linear and branched polyethylenes (LLDPE, LDPE) were used as model matrices and additional blends (80/20%, 50/50% and 20/80% LDPE/LLDPE w/w) of pure resins were also studied. Moreover, as properties of stretched films are highly dependent on processing conditions, the influence of the draw ratio was also investigated. Contrasted mechanical response in strain of the LDPE and LLDPE films under stretching were observed and justified by differences in their rheological behavior due to long branch chains (LCB) in LDPE. The modeled ultimate stress stored in LDPE and LLDPE films was compared to the shrinkage stress measured by Dynamic Mechanical and Thermal Analysis (DMTA). Both stresses were found to be in the same order of magnitude which constitutes an interesting result for the prediction of heat-skrinkability of stretched polymer films.
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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 | 0.001 | 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".