Nylon 6 and its blends with a polyamide block copolymer were prepared by solvent blending and co-precipitation process.The samples were melted at 260℃ and then cooled at a rate of 30 K/min to obtain the controlled cooling samples (CCS).Investigations were carried out on the influence of thermal treatment on crystal melting behavior and crystal structure of nylon 6 and the blends by differential scanning calorimetry (DSC)

wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM).Measurements were taken after annealing at 190℃ with varied time from 0 h to 48 h.The results indicated that the existing of the polyamide block copolymer affected the crystal behavior and the crystal structure of nylon 6

comparing to those of pure nylon 6 under the same thermal conditions.The pure nylon 6 tends to form α crystals

but it in the blends forms γ crystals.It was also found that annealing treatment had different effects on these two kinds of samples.For Nylon 6

annealing treatment only promoted the transformation of nylon 6 from amorphous to crystal phase

improved the crystalline structure and increased the crystal degree greatly without crystal form change.The crystal degree increased by about 61% after annealing for 48 h.For the blends

annealing treatment not only promoted the transformation from amorphous to crystal phase

improved the γ form crystalline structure and increased the crystal degree

but also resulted in the formation new α crystals.Compared with the original sample

the crystal degree increased by about 84% after annealing for 48 h.