Nylon‐6 α‐phase crystal: Chain repeat distance and modulus in the chain direction at low temperature

The chain repeat distance in the α‐phase crystal of nylon‐6 was measured from −150 to 150°C. The distance increases with decreasing temperature, indicating that the chain is not a complete planar zigzag but is twisted at room temperature. The relation between the distance and temperature changes at about −110°C and again near 40°C. Both changes seem to be related to the mechanical dispersions of the material. Young's modulus in the chain direction is 270 GN/m2 at −150°C, or 14% less than the theoretical value given by Tashiro and Tadokoro for the planar zig‐zag structure. It is not possible to determine from the (0k0) diffraction intensities whether the amide or methylene moieties are the more important in the chain twisting.