Properties of uniaxially stretched polypropylene films: effect of drawing temperature and random copolymer content
Bibliographic record
Abstract
Abstract Cast films of two linear polypropylenes (PP) having different molecular weights and their blends with 20 wt% random copolymer were prepared by extrusion. The produced cast films were then uniaxially hot drawn at T = 110 and 140°C under a draw ratio (DR) of 6 using a machine direction orientation (MDO) unit. The effects of drawing temperature and addition of random copolymer on the properties of the films were investigated. The type of crystals (spherulites or fibrils) was studied using differential scanning calorimetry (DSC). The drawing process generated a highly oriented fibrillar crystalline structure, resulting in an increase in the melting point of the films by about 10°C. The films drawn at 140°C revealed coexisting lamellae and fibrils whereas at 110°C mainly a fibrillar structure was observed. Tensile measurements showed a greater strength for the sample stretched at lower temperature (i.e., 110°C). The effect of drawing temperature and copolymer content on tear resistance was also explored. The medium‐molecular weight PP film stretched at 110°C showed greater tear resistance than at 140°C. The addition of the random copolymer into the medium‐molecular weight PP reduced the tear resistance significantly whereas the impact for the high‐molecular weight was not noticeable. Adding the random copolymer significantly decreased the haze for the films and hence drastically improved the clarity. Des feuilles coulées de deux polypropylènes (PP) linéaires avec des poids moléculaires différents et leurs mélanges avec 20% d'équivalent en poids de copolymère aléatoire ont été préparées par extrusion. Les feuilles coulées produites ont alors été étirées à chaud de façon uniaxiale à T = 110 et 140°C en vertu d'un rapport d'étirage de 6 à l'aide d'une unité d'orientation de sens machine. On a étudié les effets de la température d'étirage et l'ajout du copolymère aléatoire sur les propriétés des feuilles. Le type de cristaux (sphérulites ou fibrilles) a été étudié à l'aide de la calorimétrie à balayage différentiel (CBD). Le processus d'étirage a produit une structure cristalline fibrillaire fortement orientée, menant à une augmentation du point de fusion des feuilles d'environ 10°C. Les feuilles étirées à 140°C ont révélé des lamelles et fibrilles coexistantes, tandis qu'à 110°C, on a observé principalement une structure fibrillaire. Les mesures de la traction ont indiqué une résistance supérieure pour l'échantillon étiré à une température basse (c.‐à‐d., 110°C). On a également exploré l'effet de la température d'étirage et du contenu en copolymère sur la résistance au déchirement. La feuille de PP de poids moléculaire moyen étirée à 110°C a démontré une résistance au déchirement supérieur qu'à 140°C. L'ajout du copolymère aléatoire dans le PP de poids moléculaire moyen a réduit la résistance au déchirement de façon considérable, tandis que l'effet pour le poids moléculaire élevé n'était pas visible. L'ajout du copolymère aléatoire a considérablement réduit le trouble des feuilles et, par conséquent, a amélioré radicalement la clarté. Can. J. Chem. Eng. © 2010 Canadian Society for Chemical Engineering
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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".