The molten caprolactam was polymerized by means of anionic ring-opening polymerization in the presence of a non-crystallizable semi-aromatic polyamide copolymer (NSAP) in order to in situ fabricate the resultant polyamide 6 blends with NSAP.The in situ blends exhibit remarkably improved strength and modulus compared with those of the virgin system.The results of the characterization by using scanning electron microscope (SEM) and dynamic mechanical analyzer (DMA) reveal that there exist a homogeneous morphology and single glass transition for the blends.It is suggested that the miscibility results from the interchange reaction during polymerization.The traces of differential scanning calorimeter (DSC) demonstrate that as compared with the virgin system

both the melting temperature and crystallinity for the blends decrease.Wide-angle X-ray diffraction (WAXD) analysis shows that the crystals exist exclusively in α form for the virgin system; however

a drastic increase in the fraction of γ form appears in the in situ blends

e.g.

with the addition of 20 wt% NSAP

the majority of crystals is in γ form.However

only a slight refinement of spherulites occurs as observed by polarized optical microscope (POM).It is indicated that the improvement in the strength and modulus for the blends results from the reduction of molecule mobility and the fraction of PA6 γ crystals as well.