Non-isothermal crystallization of poly(trimethylene terephthalate) (PTT)/clay nanocomposites

The non-isothermal crystallization of intercalated poly(trimethylene terephthalate) (PTT)/clay nanocomposites was investigated quantitatively by different methods. Non-isothermal crystallization of pure PTT can be described by the Ozawa equation, but the Ozawa theory is not valid for PTT/clay nanocomposites. The addition of clay into PTT decreases the crystallization half-time while increasing the crystallinity and crystallization rate. The PTT/modified clay nanocomposites, in turn, have a higher crystallization rate parameter, k1/n, and a lower crystallization half-time compared to unmodified clay/PTT composites. The crystallization activation energy, calculated from Kissinger equation, of PTT, PTT/unmodified clay, and PTT/modified clay composites are 100, 180, and 198-230 kJ · mol -1, respectively. Similarly, the nucleating activities of the unmodified clay and modified clays are 0.73 and 0.51-0.58, respectively. Although the addition of clay increases the crystallization activation energy, the clay still acts as an effective nucleating agent and increases the crystallization rate and crystallinity of PTT. Further, the modified nanoscale clays are more effective nucleating agents than the unmodified counterparts, and the most effective nucleating concentration of nano-clay is between 1.0-3.0 wt.-%.