Theoretical Values of the Dynamic Stretch Moduli of Fiber-Forming Polymers

Abstract

Employing concepts first applied to textile fibers by Meyer and Lotmar in calculating the elastic stretch modulus of the crystalline domain of cellulose, the moduli of crystalline polyhexamethylene adipamide (α form), and polyethylene terephthalate have been derived. The treatment employs interatomic force constants for the stretching and bending of primary valence bonds, applied to molecular geometries deduced from the crystal structures of these polymers as determined by Bunn and co-workers. The modulus of the crystal cell of the first material (nylon 66) is calculated to be 15.7×1011 dyne cm−2, while that of the second is 14.6×1011 dyne cm−2. Supposedly these are approximately the modulus values which fibers having perfectly oriented, efficiently packed molecules would have. In both cases the theoretical value is at least an order of magnitude larger than that found experimentally for actual production samples.