Equilibrium melting temperature from Hoffman-Weeks plot

Table 20.3 Results obtained for the equilibrium melting temperatures from the Hoffman-Weeks plots of the P(HB60-ET40)/ PET and P(HB80-ET20)/PET blends...

The equilibrium temperature of a polymer (blend) can experimentally be determined by a Hoffman-Weeks plot, which is a plot of the experimental melting point versus the crystallization temperature T vs. T) as presented in Figure 3.18. Extrapolation from experimental data to the r =T line results in the value of T... 

Estimates of equilibrium melting temperatures of PCL crystallites were made, for various binary and ternary systems, with the aid of Hoffman-Weeks plots. The observed melting points of PCL were between 55 ° C and 65 ° C and varied by about 3 °C with changes in from 38 °C to 48 °C. From the melting-point depressions, as a function of composition and pressure-volume temperature data, Kim and Paul estimated equation-of-state parameters. During the course of this study Kim and Paul determined specific volume data for PCL at a series of hydrostatic pressures (Fig.51) [87]. 

Figure 9.17 shows the results of the extrapolation of the equilibrium melting temperature T° based on the Floffman-Weeks extrapolation [38], in which the melting temperature is plotted for various crystallization temperatures for semicrystalline PLA. Data for this method were collected only from calorimetric measurements, and the final result of the value of the T° for PLA is close to 480 K, as obtained from different methods [22, 36]. It should be noted that the above corrected result of the for PLA using the Hoffman-Weeks extrapolation was obtained from data for samples crystallized at small supercooUngs, at high crystallization temperatures, similar to what was reported for many cases in the literature [3,39,40]. 

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