The role of interlamellar chain entanglement in deformation-induced structure changes during uniaxial stretching of isotactic polypropylene

In-situ small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) were carried out to investigate the deformation-induced structure changes of isotactic polypropylene (iPP) films during uniaxial stretching at varying temperatures (room temperature, 60°C and 160°C). From the WAXD d...

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Bibliographic Details
Published in:Polymer (Guilford) 2007-11, Vol.48 (23), p.6867-6880
Main Authors: Zuo, Feng, Keum, Jong Kahk, Chen, Xuming, Hsiao, Benjamin S., Chen, Hongyu, Lai, Shih-Yaw, Wevers, Ronald, Li, Jing
Format: Article
Language:English
Subjects:
Applied sciences
CHAINS
DEFORMATION
DISTRIBUTION
Entanglement
Exact sciences and technology
FRAGMENTATION
LAMELLAE
MATERIALS SCIENCE
Mechanical properties
national synchrotron light source
Organic polymers
Physicochemistry of polymers
POLYPROPYLENE
Properties and characterization
RELAXATION
SCATTERING
TRANSFORMATIONS
X-RAY DIFFRACTION
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Summary:In-situ small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD) were carried out to investigate the deformation-induced structure changes of isotactic polypropylene (iPP) films during uniaxial stretching at varying temperatures (room temperature, 60°C and 160°C). From the WAXD data, mass fractions of amorphous, mesomorphic and crystal phases were estimated. Results indicate that at room temperature, the dominant structure change is the transformation of folded-chain crystal lamellae (monoclinic α-form) to oriented mesomorphic phase; while at high temperatures (>60°C); the dominant change is the transformation of amorphous phase to oriented folded-chain crystal lamellae. This behavior may be explained by the relative strength between the interlamellar entangled network of amorphous chains, which probably directly influence the tie chain distribution, and the surrounding crystal lamellae. It appears that during stretching at low temperatures, the interlamellar entanglement network is strong and can cause lamellar fragmentation, resulting in the formation of oriented mesomorphic phase. In contrast, during stretching at high temperatures, the chain disentanglement process dominates, resulting in the relaxation of restrained tie chains and the formation of more folded-chain lamellae.
ISSN:0032-3861
1873-2291
DOI:10.1016/j.polymer.2007.08.065