Of fractional free volume

Modes of Expression of Fractional Free-Volume at Glass Temperature... 

Because of the considerations noted above, in translating PALS data into a measurement of fractional free volume,/, two approaches have been used. The first [Kobayashi et al., 1989] assumes that the o-Ps intensity, I3, is a measure of the number density of holes in the amorphous phase ... 

It has been proposed that the shift factor is a function of fractional free volume, / = Vf / v ... 

Fig. 18. Schematic illustration of fractional free volume distribution G(f) and reactivity k(f)/kg according to the free volume fluctuation model Solid line in reactivity corresponds to 4 K and dashed line to 288 K...

FIG. 12-8. Diffusion coefficient of n-hexadccane at 2S°C through random styrene-butadiene copolymers plotted against reciprocal of fractional free volume calculated from equation 8. Open circles, uncross-linked samples black circles, cross-linked. Lines drawn with slope of — 1/2.3Q3 as specified by equation 7. (Rhee and Ferry. ) Reproduced, by permission, from the Journal of Applied Polymer Science. 

The introduction of fluorine in the form of trifluoromethyl groups (-CF3) in polymer lead to great benefits for improving polymer solubility. This is due to the increase of fractional free volume that limits chain packing density and hence increases solubility and process-ability. We have reported several new aromatic diamine monomers containing trifluoromethyl groups for the synthesis of soluble and... 

The large change of specific volume and hence of fractional free volume of the amorphous component of deformed semi crystalline polymers is a straightforward consequence of the intimate coupling of amoorphous and crystalline component. The former consists of free chain ends, chain loops, and tie molecules which are on one or at both ends fixed in the crystal lattice. This fact prevents the lateral contraction of amorphous layers sandwiched between parallel lamellae so that the Poisson ratio of such amorphous component is closer to zero than to. 5 characteristic for fully amorphous rubber.>291... 

It is more convenient to talk in terms of fractional free volume,/, which is defined as / = Vf/V, At and below the Tg,fis given by fg= Vf/V and can be considered as being effectively constant. Above the Tg there will be an important contribution to Vf from the expansion of the melt. The free volume above Tg is then given by... 

Fig. 20 Dependence of the increment of fractional free volume on cell dimensions for a PU network [127]...

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