Reversible and irreversible variation of the superstructure of highly oriented low‐density polyethylene during heat treatment

Abstract

The small‐angle x‐ray scattering (SAXS) intensity of highly‐oriented, low‐density polyethylene (LDPE) with fixed draw ratio has been investigated during several heating and cooling cycles. Using a three‐dimensional, monoclinic, paracrystalline superlattice to describe the superstructure of the sample, it has been possible to calculate the SAXS patterns completely. A very large irreversible variation of the superstructure during the first heating cycle, and a smaller reversible variation of the average size and distance of the crystallites during subsequent temperature cycles, could be obtained. These results can be explained using the thermodynamic theory of crystallization of polymer multicomponent systems of Kilian.

Small-Angle X-ray Scattering on Melt-Spun Polypropylene Fibers: Modeling and Data Reduction

“…To analyze SAXS data from as-spun iPP-fibers, we used a model proposed by Wilke for partially oriented polymers − based on previous considerations by Deas and adapted it to our samples. By evaluating the actual scattering data with this model, we gain up to seven parameters describing the structure of the fibers.…”

Investigation of the superstructure of polymers during deformation by synchrotron radiation

“…For the special case of a monoclinic lattice, we arrive at the following relations (Wilke, 1983;Fronk & Wilke, 1986): …”

Superstructural model for small-angle x-ray scattering: application to nylon 6 fiber

“…From the above definitions on the coordinate systems along with On the basis of assumption B, 7av(p*, 9*, *) can be written as follows, taking into account eq 3a-c: 7av(p*, 9*, ip*) = f 7(r*x, 9*x, i * ) )( ) sin a da (4) Jo Finally, according to assumption C, the experimentally measurable intensity 7(r*, 9*) can be obtained by averaging 7av(r*, 9*, *) against * over the range 0-2 , i.e. If eq 1 is inserted into eq 4 and then eq 4 into eq 5, therefore, the final expression of 7(r*, 9*) becomes 7(r*, 9*) = So So S-Mr*2' 6*2' ¥^2)Q(S)D(a) sin a dd da dip* = So So J']rA(b)Q( 6)D(a) sin a da dip* (6) where 7x(b) = ¿1(p*2, 9*2, <p*2) is the scattered intensity by a single basic scattering unit, b being the scattering vector in the (p*2, 9*2, ip*2) system. The resulting 7(r*, 9*) represents relative intensity.…”