DEFORMATION AND STRUCTURE OF CYLINDRICAL SPHERULITES IN TRANSCRYSTALLINE POLYETHYLENE - DETECTION AND CHARACTERIZATION OF PSEUDOMONOCLINIC CRYSTALLINE COMPONENT

The crystalline structure and the deformation of cylindrical spherulites were studied in transcrystalline polyethylene. The experimental results indicate that the cylindrical “spherulites” are comprised of symmetrically packed, specifically oriented lamellae which have their longest axis aligned predominantly with the long axis of the cylindrical spherulites. the long axis being normal to the plane of the polymer film. From the crystallographic data it is concluded that the banded structure observed is the result of lamellar cooperative twisting similar to that found in symmetric spherulites. The distribution of orientations observed in the X-ray diagrams supports evidence in the photomicrographs which suggests that the cylindrical “spherulites” start to grow as spheres in an umbrella-like fashion until they impinge on neighboring spherulites. From then on their growth is restricted to one direction. Under the force of lateral stretching (draw direction normal to the long axis of the spherulites) the lamellar ribbons within the spherulites are first found to spread apart to a certain degree with the retention of overall cooperative twisting. Subsequently they tilt, aligning their longest axis with the direction of stretching, pull out from the spherulitic aggregates, and untwist. Soon thereafter, reorientation into a new fiberlike structure occurs in which the unit cell c axis is preferentially oriented in the draw direction, as evidenced by the X-ray diffraction results. A pseudomonoclinic crystalline component was detected in this transcrystalline polyethylene and the unit cell parameters were established. This pseudomonoclinic component was also observed in all forms of crystalline polyethylene which we investigated and is considered likely to be a feature common to all polyethylenes. One possible manner of formation of this component is given in terms of a slightly different packing of the folded polymer chains in a somewhat strained lattice array. The proposed pseudomonoclinic unit cell accounts for all “extra” reflections observed in X-ray diagrams of polyethylenes we have investigated. © 1969, American Chemical Society. All rights reserved.