Influence of Annealing on Structure of Nylon 11

Differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and density techniques have been used to investigate the structural parameters of the solid state of Nylon 11 annealed at different temperatures. The equilibrium heat of fusion Δ and equilibrium melting temperature were estimated to be 189.05 J g-1 and 202.85 °C respectively by using the Hoffman−Weeks approach. The degree of crystallinity (W c,x) ranged approximately 24−42% was calculated by WAXD and compared with those by calorimetry (W c,h) and density (W c,d) measurements. The radius of gyration R g, crystalline thickness L c, noncrystalline thickness L a, long period L, semiaxes of the particles (a, b), electron-density difference between the crystalline and noncrystalline regions η c − η a, and the invariant Q increased with increasing annealing temperature. The analysis of the SAXS data was based upon the particle characteristic function and the one-dimensional electron-density correlation function. An interphase region existed between the crystalline and noncrystalline region with a clear dimension of about 2 nm for semicrystalline Nylon 11. Instead of the traditional two-phase model, a three-phase model has been proposed to explain these results by means of SAXS.