5 divided by R is equal to the heat of mixing, where R is the gas constant.
The heat of mixing is almost independent of the sample thickness.
The calculated heat of mixing was negative for all specimens, and was not affected by the specimen thickness and compression loads.
Heat of mixing is introduced as a guide for phase stability predictions of polymer mixtures, and an appropriate equation is presented for it.
It must be noted that the noncombinatorial entropy contribution that has not been taken into account in Eq 1 can also affect the Gibbs free energy of mixing (9), but for polymer mixtures it has been demonstrated that the heat of mixing contribution often dominates the other contributions (10, 11).
The first method utilizes the Hess cycle to calculate the heat of mixing for a polymer mixture by measuring the heat of mixing of each component in the same solvent.
Thus the temperature dependence of [varphi] is simply the sum of the molar heat of fusion of the additive and its partial molar heat of mixing with the polymer.
f], implying a negative heat of mixing, and the excess entropy of mixing is slightly negative.
The equilibrium-swelling ratio can be curve-fitted to a van't Hoff plot, and the heat of mixing [delta]H for different dosages are listed in Table 2.
The heat of mixing is almost independent of dosa ge in the range of [phi] [leq] 300 kGy, but becomes lower at [phi] = 400 kGy.
Another example where a negative heat of mixing between block and blend component has been found to result in a good compatibilizing effect is the emulsifying activity of poly(styrene-b-methyl methacrylate) in poly(vinylidene fluoride)/Noryl blends studied by Outhadi et al.
In the system PS/PMMA a negative heat of mixing is introduced between one of the graft copolymer constituents and one of the blend components.