PROBLEMS RELATING TO LONG-PERIOD DETERMINATION IN POLYETHYLENE SHISH-KEBAB STRUCTURES

The X-ray long periods from high molecular weight injection molded pol yethylene (PE) with a shish-kebab structure have been compared with va lues derived from electron micrographs. It is shown that while small a ngle X-ray scattering (SAXS) presents two long periods, the direct mea surements from transmission electron microscopy (TEM) furnish only the lower SAXS periodicity. In an attempt to clarify this discrepancy of results, laser light diffraction and Fourier transformation of electro n micrographs have been undertaken. Using this method two long periods are found in all regions investigated. Results are discussed in terms of the role played by the structured or ''weakly crystalline'' interl amellar parts, containing a lower electron density, which are neglecte d by the small angle scattering of X-rays and which give rise in parti cular regions to larger scattering periodicities.