Abstract
This paper presents an investigation on the row structures formed by two different kinds of linear-low-density polyethylenes when nucleated on highly oriented polyethylene fibers. The conditions of crystallization have been selected to cover a wide range of temperatures and times in order to study the circumstances giving rise to instability in growth fronts. In both cases the non-crystallizable molecular species which accumulate at the growth front of the row structure during crystallization lower the supercooling causing a progressive decline in the growth rate and an associated coarsening of texture with an increase of interlamellar separation and a wave-like interface. Unstable growth with faster growing protrusions may also develop for Ziegler–Natta catalysed polymer; this does not occur under all crystallization conditions but has only been found when the concentration of the segregated species reaches a sufficient value. This is the case at relatively low crystallization temperatures at which growth is much faster than the diffusion rate of segregated species. At higher temperatures, the growth rate falls increasingly from the beginning of crystallization but stabilizes, together with the coarsening (separation of lamellae) at the last stages. In this steady-state condition the growth rate is depressed to a value equal to the diffusion rate of segregated species.
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Abo el Maaty, M. On Stable and Unstable Growth of Row Structures of Linear-Low-Density Polyethylenes. Polym J 31, 778–783 (1999). https://doi.org/10.1295/polymj.31.778
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DOI: https://doi.org/10.1295/polymj.31.778