A comparison of annealing process and nucleating agent (zinc phenylphosphonate) on the crystallization, viscoelasticity, and creep behavior of compression-molded poly(lactic acid) blends

In this study, the thermal crystallization, viscoelastic property, and creep behavior of poly(lactide acid)/zinc phenylphosphonate (PLA/PPZn) blends were compared with those of annealed PLA. The results revealed that PPZn exhibited an excellent nucleating effect for the crystallization of PLA. The isothermal crystallization half-time (t1/2) of amorphous PLA (PLAam) at 130 °C was 28.1 min, whereas all the t1/2 values of PLA/PPZn blends were less than 1 min. In addition, the blends showed better thermal resistance than the annealed PLA. The storage modulus (E′) of all the PLA/PPZn blends was higher than that of the annealed PLA at temperatures higher than the Tg of PLA. However, the modulus of rupture (MOR) of PLA/PPZn blends decreased with increasing PPZn concentration in the PLA matrix, whereas there was no noticeable difference for all the annealed PLA. Regarding the creep behavior, the predicted modulus reduction of PLAam was 42.9% at 60 years by time-temperature superposition principle (TTSP) method. In contrast, the reductions in modulus levels of all the PLA/PPZn blends and the annealed PLA were still less than 33% over the 60-year period.