Degree of crystallinity determination

Fig. 535 Avrami plots showing the growth of the relative degree of crystallinity (

The crystal lattice parameters observed for these copolymers by X-ray diffraction are found to be almost identical to those of the P(3HB) homopolymer. The degree of crystallinity determined from the X-ray diffraction decreases steeply from 60 to 23% as the 3HP content in the copolymers increases from 0 to 37 mol%. The trends of composition dependence of the thermal properties and the X-ray diffraction are very similar to those for P(3HB-co-4HB) but not to those for P(3HB-co-3HV), as already mentioned above. Thus, it is reasonable to assume that in the P(3HB-co-3HP) samples containing up to 37 mol% 3HP unit, the 3HB units exist in the crystalline as well as in the noncrystalline regions, while almost all of the 3HP units exist only in the latter. To further investigate this point, the NMR relaxation times have been measured for the films cast from a chloroform solution. 

In any case one speaks about the degree of crystallinity of the materials, being a measure of the volume fraction of the crystalline part of the material. This parameter is, however, not uniquely defined, but varies considerably with the method used for its determination. The degree of crystallinity determined by means of x-ray diffraction is often call the x-ray crystallinity, Xc- In the spirit of Ruland analysis [36]... 

Polymer stereoregularity is important since the morphology of the macromolecule depends on crystallization and the degree of crystallinity determines, in the end, several physical properties such as density, mechanical properties, as well as thermal properties. Atactic polymers have difficulties in crystalling they are amorphous or show a low degree of crystallinity, while the degree of crystallinity in isotactic and syndiotactic polymers is high. 

CA resonance line vs. degree of crystallinity determined by x-ray analysis. native cellulose, o regenerated cellulose,... 

Approximate degree of crystallinity determined by the areas of crystalline and amorphous diffractions on WAXD. The values in the parentheses are those after annealing under the conditions indicated. 

Fig. 16. Integrated fraction of the downfield component of the C4 resonance line versus degree of crystallinity, /, determined by X-ray analysis., Native cellulose O, regenerated cellulose , mercerized cotton and ramie. (The data for regenerated cellulose samples, except for cupra rayon fibres, were reproduced from ref. 45).

Molecular weight of recycled HDPE as measured by size-exclusion chromatography can be correlated with diffuse reflectance near- and mid-infrared spectroscopy (NIR/MIR). The RMSEP obtained with MIR data was 360 and with NIR data was 470. The degree of crystallinity determined by DSC can also be correlated to the spectra. The prediction ability of this model was poor in the 1100 to 1900 nm region, however the 2000 to 2500 nm region yielded better results. Four PC factors explained the most of the variance in the spectra and the RMSEP was 0.4% wt. [51]. 

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