Anisotropy and structure in uniaxially stretched amorphous high polymers

Abstract

AbstractWhen an amorphous polymer is stretched uniaxially, the chain molecules are oriented along the stretching direction. Orientation causes an anisotropy of the macroscopic physical properties with rotational symmetry about the stretching direction. The phenomenological treatment of the properties exhibited by a uniaxially oriented polymer follows mathematical methods known from crystal physics. Earlier data on anisotropy of linear thermal expansion, thermal conductivity, and linear compressibility for PVC are quantitatively explained with the aid of a known distribution function. The complete set of the five elastic compliances of hot‐stretched PVC are experimentally determined as function of stretch up to 180%. The correspondent compliances for the perfectly oriented material are calculated yielding, e.g., 5 × 1010 dynes/cm.2 for the Young's modulus along the chains. Finally, the lengths of the statistical segments in natural rubber and polychloroprene are evaluated from thermal conductivity measurements on these substances in the strained state. As is expected the polyisoprene chains prove to be considerably more flexible than those of polychloroprene.