TY - JOUR
T1 - Shear-induced crystallization of isotactic polypropylene within the oriented scaffold of noncrystalline ultrahigh molecular weight polyethylene
AU - Avila-Orta, Carlos A.
AU - Burger, Christian
AU - Somani, Rajesh
AU - Yang, Ling
AU - Marom, Gad
AU - Medellin-Rodriguez, Francisco J.
AU - Hsiao, Benjamin S.
PY - 2005/9/23
Y1 - 2005/9/23
N2 - Shear-induced crystallization of isotactic polypropylene (iPP) within the oriented scaffolds of noncrystalline ultrahigh molecular weight polyethylene (UHMWPE) was investigated by means of in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). The study was carried out using iPP/UHMWPE blends under isothermal crystallization at 145 °C (i.e., above the melting point of polyethylene) and step shear (shear rate=60 s-1, duration=5 s) conditions. The oriented and isotropic iPP crystalline phases were extracted from the 2D WAXD pattern, and their kinetics data were evaluated with the Avrami equation. The dominant component in the oriented iPP phase was a kebab structure, whose nanostructure dimensions were determined by a novel SAXS analysis scheme. The minor non-crystalline but oriented UHMWPE component played a key role in the nucleation of iPP, which could be explained in terms of mutual diffusion at the interface, resulting in a significant increase in the relaxation time of iPP chains. As a result, after shear, the interfacial iPP chains could also retain their orientation and formed oriented nuclei to initiate the kebab growth.
AB - Shear-induced crystallization of isotactic polypropylene (iPP) within the oriented scaffolds of noncrystalline ultrahigh molecular weight polyethylene (UHMWPE) was investigated by means of in situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD). The study was carried out using iPP/UHMWPE blends under isothermal crystallization at 145 °C (i.e., above the melting point of polyethylene) and step shear (shear rate=60 s-1, duration=5 s) conditions. The oriented and isotropic iPP crystalline phases were extracted from the 2D WAXD pattern, and their kinetics data were evaluated with the Avrami equation. The dominant component in the oriented iPP phase was a kebab structure, whose nanostructure dimensions were determined by a novel SAXS analysis scheme. The minor non-crystalline but oriented UHMWPE component played a key role in the nucleation of iPP, which could be explained in terms of mutual diffusion at the interface, resulting in a significant increase in the relaxation time of iPP chains. As a result, after shear, the interfacial iPP chains could also retain their orientation and formed oriented nuclei to initiate the kebab growth.
KW - iPP
KW - Shear-induced crystallization
KW - UHMWPE
UR - http://www.scopus.com/inward/record.url?scp=24144498479&partnerID=8YFLogxK
U2 - 10.1016/j.polymer.2005.05.136
DO - 10.1016/j.polymer.2005.05.136
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:24144498479
SN - 0032-3861
VL - 46
SP - 8859
EP - 8871
JO - Polymer
JF - Polymer
IS - 20
ER -