Intrinsic Differences between Nylon 6 and Nylon 66 Industrial Fibers: Micromechanical and Molecular Analysis

In airdrop applications we noted significant performance advantages of nylon 6 over nylon 66. These advantages are noted in bending fatigue, abrasion resistance and retention of properties on repeated use. To explain this advantageous behavior of nylon 6 we carried out comprehensive morphological and micromechanical analyses. These in turn, provided a better understanding of the role of subtle structural differences between nylon 6 and nylon 66 in the performance of fabrics used in parachutes. The study showed that the outstanding bending fatigue resistance and retention of properties of nylon 6 on repeated use must be attributed to a much narrower distribution of long period, anti-parallel arrangement of molecules in the alpha crystalline form, and the existence of gamma crystalline form which is energetically close to the alpha form with shorter repeating unit.