Mechanical properties and superstructure of high‐modulus and high‐strength PET fiber prepared by zone annealing

The relationships between mechanical properties and superstructure of the poly(ethylene terephthalate) fiber prepared by a new annealing method called zone annealing method were investigated. The effectiveness of zone annealing was compared with three other annealing methods, namely, annealing under release, annealing at constant length, and annealing under tension. The very high modulus and strength of the zone‐annealed fiber were directly attributed to the large number of tie molecules connecting the crystallites and to the high orientation of the amorphous region.