Probing the Flow-Induced Shish-Kebab Structure in Entangled Polyethylene Melts by Synchrotron X-ray Scattering

Journal Article · Mon Jan 01 04:00:00 EST 2007 · Journal of Applied Crystallography

OSTI ID:930374

Keum, J; Zuo, F; Hsiao, B

In-situ rheo small-angle X-ray scattering (SAXS) and rheo wide-angle X-ray diffraction (WAXD) techniques were used to investigate the flow-induced crystalline structure in entangled melts of ultrahigh-molecular-weight polyethylene (UHMWPE)/low-molecular-weight polyethylene (LMWPE) blends (0, 2 and 5 wt% of UHMWPE). Immediately after a step shear at 415 K, SAXS and WAXD results confirmed that only the shish structure was formed in the melts without kebabs. The topological deformation of entangled UHMWPE chains in the blend was responsible for the formation of shish. The missing kebab growth in the presence of shish indicated that secondary nucleation of coiled chains on the shish surface was frustrated at high temperatures close to the equilibrium melting temperature (418.5 K). When the temperature was quenched to 407 K, both blends (but not pure LMWPE) clearly exhibited oriented kebab growth. An Avrami analysis was applied to investigate the nucleation and growth of kebabs. Results indicated that kebabs were probably grown under athermal nucleation and diffusion-controlled conditions. In addition, the crystallization rate under predetermined nucleation was strongly governed by the concentration of shish.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: Doe - Office Of Science
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 930374
• Report Number(s): BNL--81096-2008-JA
• Journal Information: Journal of Applied Crystallography, Journal Name: Journal of Applied Crystallography Vol. 40; ISSN 0021-8898; ISSN JACGAR
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
43 PARTICLE ACCELERATORS
CRYSTAL STRUCTURE
CRYSTALLIZATION
DEFORMATION
MELTING
NUCLEATION
POLYETHYLENES
SCATTERING
SHEAR
SMALL ANGLE SCATTERING
SYNCHROTRON RADIATION
X-RAY DIFFRACTION
national synchrotron light source