As opposed to the
isothermal process, the isobaric process is a Hamiltonian process which means that it may be obtained by adding extra terms to the Lagrangian [28, 36].
For the investigation of the
isothermal process of pressure solidification the process was conducted with a compression speed of 1.6 MPa/s and a cooling rate of 3 K/ min as follows.
For
isothermal processes, temperatures of 130 and 150[degrees]C were used to evaluate the influence of temperature on the stress distribution.
It is difficult, therefore, to estimate accurately the value of the crystallinity directly from the crystallization curve in the initial stage of the
isothermal process, especially at low crystallization temperatures.
It is noteworthy that in the analysis of the crystallization kinetics, the cooling time has been previously subtracted and only the
isothermal process has been considered, as it has been described in the rheological experimental section (points A and B).
The only way in which both Eqs 2 and 10 are jointly satisfied at all times for an
isothermal process is when
Then, the Avrami model can be used to describe the development of the relative degree of crystallization in the
isothermal process according to the following equation:
It is also observed that the [F.sub.(T)] parameter decreases with increasing VA content in the blends, indicating an increase of overall crystallization rate, as also observed in the
isothermal process.