Dynamic Response of Stereoblock Elastomeric Polypropylene Studied by Rheo-Optics and X-ray Scattering: 2. Orthogonally Oriented Crystalline Chains
- SLAC
A combination of tensile stress, rheo-optical birefringence, and wide-angle X-ray scattering (WAXS) was used to probe the dynamic response of the low-tacticity ether-soluble (ES) fraction of elastomeric polypropylene (ePP) derived from metallocene 2-arylindene hafnium catalyst. The ES fraction has isotactic pentad distribution [mmmm] = 21% and a very low amount of crystallinity ({le} 2% by differential scanning calorimetry and WAXS). In tensile stretching and step-strain shearing, ES exhibits unusual deformation behavior of crystalline chains preferentially oriented orthogonal relative to the deformation axis. Under deformation, WAXS shows arcing along the meridian axis at a scattering angle 2{theta} = 16.0{sup o} (d = 0.551 {+-} 0.002 nm) which coincides with one of the characteristic reflections of the {beta}-form; but the higher order reflection for the {beta}-form at 2{theta} = 21.3{sup o} is not observed. The meridional arcing, which signifies crystallization of the low-tacticity fraction of ePP, is also observed when ES is blended with higher tacticity fractions of ePP. The meridional arcing, however, is observed at 2{theta} = 14.0{sup o} corresponding to (110) reflection of the {alpha}-form, instead of at 2{theta} = 16.0{sup o} for the neat ES. The crystallization in the {alpha}-form offers evidence of co-crystallization of the ES fraction with the higher-tacticity components in the same crystalline form as the host matrix. We believe that the co-crystallization occurs through an epitaxial growth in the ac-faces of the {alpha}-form.
- Research Organization:
- Stanford Linear Accelerator Center, Menlo Park, CA (US)
- Sponsoring Organization:
- USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 799987
- Report Number(s):
- SLAC-PUB-9345
- Country of Publication:
- United States
- Language:
- English
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