Thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate)/poly(hexamethylene isophthalamide) blends

This work examines the thermal properties and phase morphology of melt-mixed poly(trimethylene terephthalate) (PTT)/poly(hexamethylene isophthalamide) (PA 61) blends. Two temperatures, i.e., 250 and 260°C, are used to prepare the blends, respectively. Differential scanning calorimetry results indicate the immiscible feature of the blends. It is thus concluded that the ester-amide interchange reaction hardly occurred in the PTT/PA 61 blends. Depending on the composition and mixing temperature, the crystallization ability of PTT in the blends is either enhanced or hindered. Basically, a lower PA 61 content shifts the PTT melt crystallization to a higher temperature, whereas a higher PA 61 content causes an opposing outcome. The original complex melting behavior of neat PTT becomes more regular after the incorporation of 60 wt % or 80 wt % of PA 61. Thermogravimetry analyses (TGA) show that the thermal stability of the blends improves as the PA 61 content increases. The two-phased morphology of the blends is examined by scanning electron microscopy (SEM). Polarized light microscopy (PLM) results reveal that the PTT spherulites become coarser with the inclusion of PA 61; only smaller/dispersed crystallites are observed in the blend with 20 wt % of PTT.