Estimation of the Degree of Crystallinity of Partially Crystalline Polypropylenes Using ^{13}C NMR

Abstract

The paper deals with a method for the estimation of the degree of crystallinity for partially-crystalline isotacticpolypropylenes (i-PP) using high-resolution solid-state 13 C NMR. For this purpose direct polarization 13 C MAS NMR spectra were measured for i-PP samples with dierent degrees of crystallinity at 98• C. The areas beneath the resonance lines in these spectra correspond to the number of carbons in particular functional groups, while the widths and shapes of the lines reect the degree of crystallinity, crystalline modications, distribution of chain conformations and the chain mobility. The 13 C MAS NMR spectra, measured using appropriate combination of delay time and high proton decoupling eld, made it possible to detect only amorphous domains in the sample. This enabled identication of the lines associated with the amorphous domains in the complete 13 C MAS NMR spectra and provided sucient information for reliable estimation of the degree of crystallinity. The heteronuclear Overhauser enhancement of the 13 C NMR signals due to short delay time was taken into account in our calculations.

Quantifying the fragmentation of polypropylene upon exposure to accelerated weathering

“…The long-term degradation proceeds similar for both PP experiments. The 13 C CP MAS NMR spectra for both sets of weathering experiments (with and without stabilizer combination) show the typical resonances for the amorphous and crystalline regions of PP [52] (Fig. S10, S11).…”

“…13 C CP MAS NMR spectrum of the PP particles with stabilizer prior to weathering with signal assignment. In the enlarged PP spectra (blue and orange rectangle) the differences of the resonances of the amorphous (signal a1 and b1) and crystalline (signal a2 and b2) phase become visible [52]. Figure S11.…”

“…13 C CP MAS NMR spectra of the PP particles with (A) and without (B) stabilizer for 0, 400 and 3200 h weathering time. Upon irradiation, a shift of signal intensity fromthe amorphous phase resonances (30 ppm, 48 ppm) to the crystalline phase resonances (28 ppm, 46 ppm) is observed [52]. The spectra are normalised to the integral of the backbone signal (35-20 ppm and 55-35 ppm).…”

One-pot low temperature synthesis and characterization of hybrid poly(2-pyrrolidone) microparticles suitable for protein immobilization

“…(For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.) [25]. Because magnetization recovery is controlled by the 13 C spin-lattice relaxation, these experiments demand very long acquisition times.…”

Unravelling potential reaction intermediates during catalytic pyrolysis of polypropylene with microscopy and spectroscopy

“…5A show broad peaks at ∼22, 27, and 45 ppm, related to CH 3 , CH and CH 2 carbons of polypropylene, respectively ( Fig. 5A, top panel ), 44 which then almost fully disappear at the later stage ( Fig. 5A, lower panel ).…”