Amorphous regions in polymers

In addition to longitudinal acoustic modes (section 4.10), the low-frequency regions of Raman spectra often contain rather broad, ill-defined bands. While these can sometimes be ascribed to specific intra- or inter-molecular vibrations, work has suggested they may be due to fracton vibrational modes localised in disordered regions or blobs [241]. Analysis of the bandshape has been used to measure the size of the disordered regions for example, -50A blobs were found in amorphous PET and PMMA [242]. 

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Oxygen can permeate amorphous regions in polymers and intercept some of the radicals produced in the photo-initiation steps (1+, 6, 8) (Table l). 

Oxygen can permeate amorphous regions in polymers and intercept some of the radicals produced in the photo-initiation steps (jt, 5., , 8) (Table i). In PP no more than one in six of the photo-initiation steps can be expected to result in a free tert.-peroxy radical (PPO2. reaction 3) the remainder of the initiation steps... 

The Tg of P-plastomers changes as a function of ethylene content. The Tg decreases with increasing ethylene content, primarily due to an increase in chain flexibility and loss of pendant methyl residues due to incorporation of ethylene units in the backbone. It is well known that PP has a Tg of 0°C, and polyethylene a Tg< —65°C. The addition of ethylene to a propylene polymer would therefore be expected to decrease the Tg, as is observed here. A secondary effect would be the reduction in the level of crystallinity associated with increasing ethylene content, which is expected to reduce the constraints placed upon the amorphous regions in proximity to the crystallites. Thus, an increase in ethylene content will result in a lower T as well as an increase in magnitude and a decrease in breadth of the glass transition. 

Rastogi, S. and Terry, A.E. Morphological implications of the interphase bridging crystalline and amorphous regions in semi-crystalline polymers. Vol. 180, pp. 161-194. 

Amorphous phase, of polymers, 20 400 Amorphous polymers, 10 203 crystallization of, 19 844 Amorphous red selenium, 22 74 Amorphous regions, in fibers, 11 171 Amorphous resins, use in thermoforming, 19 555... 

Here r is the distance between the paired protons, ft is the magnetic moment of the proton. However, the molecular mobility in the amorphous region in the polymer where the rotation around C—C bonds is hindered is not so simple as expected from Eq. (17). The equation cannot adequately reproduce the medium component of the spectrum. It is reported by Bergmann and Nawotki14 that for actual spectra for polymers the following expression reproduces more adequately the medium component ... 

Morphological Implications of the Interphase Bridging Crystalline and Amorphous Regions in Semi-Crystalline Polymers... 

The traditional model used to explain the properties of the (partly) crystalline polymers is the "fringed micelle model" of Hermann et al. (1930). While the coexistence of small crystallites and amorphous regions in this model is assumed to be such that polymer chains are perfectly ordered over distances corresponding to the dimensions of the crystallites, the same polymer chains include also disordered segments belonging to the amorphous regions, which lead to a composite single-phase structure (Fig. 2.10). 

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