| Titre : |
Crystallization and orientation development in melt spinning isotactic PP of varying tacticity |
| Type de document : |
texte imprimé |
| Auteurs : |
D. Choi, Auteur ; J. L. White, Auteur |
| Année de publication : |
2002 |
| Article en page(s) : |
p. 233-243 |
| Note générale : |
Bibliogr. |
| Langues : |
Anglais (eng) |
| Index. décimale : |
668.9 Polymères |
| Résumé : |
We investigated the effects of tacticity on crystallization and orientation development in melt spinning isotactic polypropylene (iPP) through air. Melt-spun fibers were characterized by wide-angle X-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). The melt-spun fibers usually exhibited the monoclinic α-crystalline form, but the mesomorphic form was found under certain processing conditions. The mesomorphic structure was formed more readily in low tacticity fibers. We found certain amounts of hexagonal β-crystalline form in all of the α-form fiber samples. The amouns were generally negligibly small, but the low tacticity fibers spun at high draw-down ratios exhibited significant amounts of β-form crystals. At low spinline stress levels, some low tacticity fibers exhibited lower birefringence and chain orientation than high tacticity fibers due to a less perfect crystal structure. At certain high spinline stress levels, low tacticity fibers exhibited much higher birefringence and chain-axis orientation levels than expected. This was attributed to a reduction in epitaxial lamellar branching (a*-axis oriented group in bimodal orientation). However, the extent of lamellar branching in low tacticity fibers appeared to increase again at higher stress levels. This led to a significant decrease in birefringence and crystalline orientation. |
| Note de contenu : |
- Introduction
- Experimental : Materials - Material characterization - Melt spinning - Fiber characterization - X-ray diffraction analysis - DSC analysis - Birefringence measurement
- Results : Crystallization rates - Spinline stresses - Fiber melting temperatures and crystallinities - WAXD patterns and 2téta scans - Birefringence - Crystalline orientation factors - Amorphous orientation factors
- Discussion : Crystal structures - Birefringence and chain orientation
- Conclusions |
| DOI : |
10.3139/217.1699 |
| En ligne : |
https://drive.google.com/file/d/1i273l-u443eWki5pSWrhBDEP3xfYL60V/view?usp=drive [...] |
| Format de la ressource électronique : |
Pdf |
| Permalink : |
https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=15999 |
in INTERNATIONAL POLYMER PROCESSING > Vol. XVII, N° 3 (09/2002) . - p. 233-243
Aller sur edunet
Accueil
Crystallization and orientation development in melt spinning isotactic PP of varying tacticity in INTERNATIONAL POLYMER PROCESSING, Vol. XVII, N° 3 (09/2002)
