X‐ray diffraction, Raman, and differential thermal analyses of the thermal aging of a Kevlar®‐PBI blend fabric
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Bibliographic record
Abstract
Abstract A previous study of the effects of thermal aging on the tensile properties of a fabric made of a 60–40 wt % blend of Kevlar and PBI fibers has shown that exposure to elevated temperatures between 190 and 320°C results in a rapid decrease in tensile breaking force retention. In this article, X‐ray diffraction and Raman spectroscopy analyses were carried out to evaluate the consequences of thermal aging on the material's crystallinity. Differential thermal analyses were also undertaken to examine the evolution of the glass transition temperature of PBI following thermal exposure. X‐ray diffraction profiles show a gradual increase in the crystallinity with temperature and aging time, whereas a complete disappearance of spectral lines for aged samples in Raman analysis suggests instead a decrease in crystallinity as a consequence of exposure to elevated temperatures. The seemingly contradictory outcome obtained when using the two techniques led to the proposal of a new, alternative hypothesis to explain the observed results. This hypothesis involves two simultaneous events that occur during thermal aging: the increase of crystallite size in the direction parallel to coplanar sheets, and the disruption of the crystalline lattice in the direction perpendicular to those sheets. The glass transition temperature of PBI was found to shift towards the lower temperatures after thermal aging, a phenomenon that can be associated with random polymer chain scission caused by thermal aging. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers
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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) | 0.001 | 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 it