X-Ray and thermal studies of nylon 5,7

The unit cell and probable space group of Nylon 5,7 has been determined. The unit cell is monoclinic with the dimensions a = 0.483 nm, b = 0.935 nm, c = 1.662 nm, and γ = 58.9°. The space group is probably P_b which is noncentrosymmetric. Rolled, annealed samples show three-dimensional orientation. The melting point peak of a rapidly cooled sample is about 213°C when it is heated at 20°C/min. Slow cooling, ≤°1°C/min generates a higher melting species, T_m = 228°C. Crystallinities are in the normal nylon range, up to 50% for a slow cooled sample.