Poly(butylene terephthalate)/montmorillonite nanocomposites: Effect of montmorillonite on the morphology, crystalline structure, isothermal crystallization kinetics and mechanical properties

•Effect of amount of clay content, its dispersion on crystalline structure of PBT.•Regime break temperature shifts to lower temperature for PCN4 up to 197°C.•Tensile modulus enhanced up to 95% for PCN3 compared to PBT. Nanocomposites (PCNs), based on poly(butylene terephthalte) (PBT) and organoclay (Cloisite-15A) MMT were prepared by melt intercalation compounding process. The nanoscale dispersion and the microcrystal structure studied qualitatively using; X-ray diffraction (XRD) and electron microscopy (SEM, TEM and AFM). The XRD results indicated that the crystal size is highly dependent on the crystallization temperature. The isothermal crystallization kinetics of PBT in PCNs analysis indicated that the overall crystallization of PBT involved heterogeneous nucleated three-dimensional spherical primary crystallization growth process. The crystallization rate, however, is dependent on the PCN-composition, crystallization temperature and the dispersion state of clay in PCNs. Further analysis, based on Hoffman-Lauritzen theory revealed that the neat PBT and PBT in PCNs crystallization follow regime-II kinetics for temperature 195°C–205°C and enters the regime-III kinetics in lower Tc range, 185°C–195°C. The improvement in mechanical properties is highly dependent on the level of clay exfoliation in PBT matrix.