A combination of DSC, SAXS, WAXD, 1H time-domain, and frequency domain NMR
measurements was used for determining the amount of rigid/crystallinity, semirigid, and soft fractions of iPP.
Changes in the rigid, semirigid, and soft fractions of isotactic polypropylene (iPP) were investigated as a function
of temperature, annealing time, and annealing temperature. The most probable iPP morphology was established
by TEM and by comparing 1H spin-diffusion data with data from multidimensional solutions of the spin-diffusion
equations. Proton NMR spin-diffusion method, which employs double-quantum (DQ) and Goldman−Shen dipolar
filters, was used in order to provide the domain thickness in iPP. The temperature dependence of spin diffusivities
was taken into account, and a semiquantitative theory is presented for this dependence in the case of amorphous
domains. A combination of 1H spin-diffusion NMR and SAXS was used to estimate the lamellar thicknesses for
nonannealed and annealed iPP samples. Annealing at temperatures above 110 °C causes increases in the lamellar
thickness and the crystallinity and a decrease in the chain mobility of rigid and semirigid fractions. The above
quantities and the chain dynamics are reported for three annealing temperatures, 134, 143, and 153 °C, and an
annealing time in the range of 15 min to 30 h. It is shown that the crystalline domains thickening during annealing
of iPP can be described by a model based on irreversible thermodynamics. A phenomenological correlation is
established between 1H transverse magnetization relaxation rate of the rigid fraction of iPP and the annealing
temperatures.
Changes in phase composition and chain mobility in injection‐molded isotactic poly(propylene), crystallized from the melt with slow cooling rate and subsequently quenched, associated with aging at temperature well above Tg for 150 and 1 000 h, are studied using time‐domain 1H solid‐state NMR and XRD. All sample exhibit physical aging when exposed to elevated temperatures, and the physical aging kinetics was observed to depend on the morphology of the homopolymer iPP and aging temperatures. The significant increase in the tensile modulus in time was observed for injection‐molded iPP. The observed property changes induced by aging are attributed to microstructural changes within the semi‐rigid and amorphous fractions.
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