Structure and reversible deformability of oriented crystallizing polymers

Abstract

Abstract The effect of reversible (elastic) extensions of oriented crystallizing polymers on long periods within them, recorded by small‐angle x‐ray diffraction, has been investigated. The reversible shift of the meridian maximum of diffraction intensity toward small angles (which means the increase of long periods) as well as the maximum diffraction intensity increase with polymer loading have been established. The agreement of relative increments of long periods and polymer‐specimen dimensions is rather common, although some instances when the period deformation exceeded the specimen deformation have been observed (for highly annealed oriented polymers). The invariability of crystallites with polymer extension (according to large‐angle x‐ray diffraction) indicates that the deformation of long periods, which are formed by the alternation of crystalline and amorphous regions along the orientation axis, is caused by crystallites transference due to stretching the amorphous interlayers between them. The increase of small‐angle diffraction intensity with the extension of oriented polymers is supposed to be due to two factors: ( 1 ) the reduction of crystallite share in long periods; and ( 2 ) the decrease of the density of extended amorphous interlayers which results in increasing the density difference of alternate crystallites and amorphous regions. The problem of more precise definition and checking of these conclusions is raised and attention is drawn to the great interest in investigating the amorphous‐region properties in oriented crystallizing polymers, which determine the mechanical properties of polymers.