0000000000660511
AUTHOR
Diana Sapoundjieva
Study of the long-period changes in samples of isotactic poly(propylene) obtained by quenching from the melt and subsequent annealing at different temperatures
The structural modifications induced in samples of isotactic poly(propylene) obtained by quenching from the melt at 100°C/s and subsequently annealed at 40, 60 and 80°C for different annealing times have been studied using simultaneous wide-angle and small-angle X-ray scattering at the synchrotron radiation source of DESY. The occurrance of two different long-period values is demonstrated. These values are related to the mesomorphic phase, existing in the starting quenched material, and to the α-monoclinic one, which settles during the annealing process, respectively.
Structural and morphological rearrangements in quenched poly(ethylene) by simultaneous SAXS/WAXS
Structure formation by crystallization from the melt in a wide range of cooling rates (0.08-1 000°C/s) in low-density polyethylene has been studied by simultaneous small- and wide-angle X-ray scattering at the synchroton radiation source of DESY. The occurrence of two periodicities, characterized by different angular position of Bragg's maxima, was observed, pointing to the existence of two types of lamellar stacks, associated with two different long period values L 1 and L 2 (L 1 > L 2 ). L 1 depends on the cooling rate, whereas L 2 is almost constant. A comparison with isotactic polypropylene is performed, where a similar phenomenon takes place. While in the case of i-PP a definite correl…
SAXS/WAXS study of the annealing process in quenched samples of isotactic poly(propylene)
The structural rearrangement in samples of quenched isotactic poly(propylene) (iPP) submitted to different annealing treatments has been studied using simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS) at the synchrotron radiation source of DESY, Hamburg. From a quantitative analysis of the WAXS profiles the values of the α-monoclinic, mesomorphic, and amorphous mass fractions coexisting in the material were determined. It is demonstrated that the SAXS patterns were characterized by two different long-period values that are attributed to α- and mesomorphic periodicity, respectively. The related α- and mesomorphic volume phase fractions, calculated from the analysis of the SAXS …