Mobile amorphous fraction

Fig. 15. 2H FT NMR spectra of the mobile amorphous fraction of LPE for various temperatures. The total magnetization was saturated first by a series of 90° pulses and then the solid echo was created after a waiting period r0 T, (amorphous) ranging from 25 to 200 ms...

Olson, B. G., Lin, J., Nazarenko, S., and Jamieson, A. M., Positron annihilation lifetime spectroscopy of poly(ethylene terephthalate) contributions from rigid and mobile amorphous fractions. Macromolecules, 36, 7618-7623 (2003). 

We may pose the following question Is the probability of o-Ps formation similar or different in the rigid versus the mobile amorphous fraction If it is similar, the overall intensity h should decrease linearly with the volume fraction of clay according... 

Fig. 21.13. Normalized dielectric strength (zle)norm as a function of the crystallinity Xc for ( )PET crystalized at T = 96°C (SWD-data). ( )Poly(butylene isophthalate)(PBI)crystallized at T = 60°C(SMTD-data [49 ). (o)Mobile Amorphous Fraction (MAF) (calorimetry data) for PET crystallized at T = 117 C (data extracted from Fig. 3 of [29]...

Fig. 22. Rigid amorphous, mobile amorphous, and crystallinity changes in PPS with crystallization temperatures (166). Mobile amorphous fraction rigid amorphous fraction and weight fraction crystallinity A.

In addition to multiple amorphous states, Wunderlich [22] has proposed coexistent dual amorphism, where the dominant characteristics are those of a mobile amorphous phase and a so-called rigid amorphous fraction (RAF). The RAF is characteristic of semi-crystalline polymers, found in many food, pharmaceutical and polymer areas, where polymer chains, as they pass from crystalline to amorphous regions, are perturbed and have properties lying between the two extremes. A property of the RAF is that it does not contribute to the step in heat capacity at the main glass transition. In fact the method of calculating the fraction of the rigid amorphous phase cp is usually to measure the crystallinity by an independent method, such as density or possibly X-ray methods, and to estimate the mobile amorphous fraction from the difference between the heat capacity steps of the sample under consideration and a 100% amorphous-generated state. The RAF is then calculated as the difference between 1 and the sum of the content of the previous phases. 

It has also been shown that in solid-state polymerisation of danol with poly(butylene terephthalate), PBT, the diol is not incorporated into the rigid fraction. The RAF was detected using DSC. The PBT chains in the rigid fraction are deemed too inflexible to take part in the transesterification reaction, in contrast to the chains in the mobile amorphous fraction [24]. The area of the RAF is one which may see significant development in food polymers, such as starch. 

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