Yong Sung Chun

Thermal properties of blends of poly(hydroxybutyrate-co-hydroxyvalerate) and poly(styrene-co-acrylonitrile)

Thermal properties of blends of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(styrene-co-acrylonitrile) (SAN) prepared by solution casting were investigated by differential scanning calorimetry. In the study of PHBV-SAN blends by differential scanning calorimetry, glass transition temperature and melting point of PHBV in the PHBV-SAN blends were almost unchanged compared with those of the pure PHBV. This result indicates that the blends of PHBV and SAN are immiscible. However, crystallization temperature of the PHBV in the blends decreased approximately 9–15°. From the results of the Avrami analysis of PHBV in the PHBV-SAN blends, crystallization rate constant of PHBV in the PHBV-SAN blends decreased compared with that of the pure PHBV. From the above results, it is suggested that the nucleation of PHBV in the blends is suppressed by the addition of SAN. From the measured crystallization half time and degree of supercooling, interfacial free energy for the formation of heterogeneous nuclei of PHBV in the PHBV-SAN blends was calculated and found to be 2360 (mN/m)3 for the pure PHBV and 2920–3120 (mN/m)3 for the blends. The values of interfacial free energy indicate that heterogeneity of PHBV in the PHBV-SAN blends is deactivated by the SAN. This result is consistent with the results of crystallization temperature and crystallization rate constant of PHBV in the PHBV-SAN blends.

Compatibility studies of sulfonated poly(ether ether ketone)-poly(ether imide)-polycarbonate ternary blends

Binary blends of the sulfonated poly(ether ether ketone) (SPEEK)–poly(ether imide) (PEI) and SPEEK–polycarbonate (PC), and ternary blends of the SPEEK–PEI–PC, were investigated by differential scanning calorimetry. SPEEK was obtained by sulfonation of poly(ether ether ketone) using 95% sulfuric acid. From the thermal analysis of the SPEEK–PEI blends, single glass transition temperature (Tg) was observed at all the blend composition. For the SPEEK–PC blends, double Tgs were observed. From the results of thermal analysis, it is suggested that the SPEEK–PEI blends are miscible and the SPEEK–PC blends are immiscible. Polymer–polymer interaction parameter (χ12) of the SPEEK–PEI blends was calculated from the modified Lu and Weiss equation, and found to range from −0.011 to −0.825 with the blend composition. For the SPEEK–PC blends, the χ12 values were calculated from the modified Flory–Huggins equation, and found to range from 0.191 to 0.272 with the blend composition. For the SPEEK–PEI–PC ternary blends, phase separation regions that showed two Tgs were found to be consistent with the spinodal curves calculated from the χ12 values of the three binary blends.

Thermal Properties of Melt-Blended Poly(ether ether ketone) and Poly(ether imide)

The thermal properties of blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) prepared by screw extrusion were investigated by differential scanning calorimetry. From the thermal analysis of amorphous PEEK–PEI blends which were obtained by quenching in liquid nitrogen, a single glass transition temperature (Tg) and negative excess heat capacities of mixing were observed with the blend composition. These results indicate that there is a favorable interaction between the PEEK and PEI in the blends and that there is miscibility between the two components. From the Lu and Weiss equation and a modified equation from this work, the polymer–polymer interaction parameter (χ12) of the amorphous PEEK–PEI blends was calculated and found to range from −0.058 to −0.196 for the extruded blends with the compositions. The χ12 values calculated from this work appear to be lower than the χ12 values calculated from the Lu and Weiss equation. The χ12 values calculated from the Tg method both ways decreased with increase of the PEI weight fraction.