Bimodal High-Density Polyethylene: Influence of the Stereoregularity of the Copolymer Fraction on the Environmental Stress Crack Resistance

Abstract

In the present study, it is demonstrated that the stereoregularity of the copolymer fraction of bimodal high-density polyethylenes (HDPEs) influences the environmental stress crack resistance. Polymer samples were characterized in terms of their semicrystalline microstructure. A certain stereoregularity was identified for the copolymer fraction, and a linear correlation between the stress crack resistance, which was assessed by the full notch creep test, and the fraction of stereoregular chains in the HDPE was established. Conceptual models to understand the action of the stereoregular copolymer chain in the slow crack growth mechanism are proposed. The results found in the present research will serve as guidelines for tailoring the properties of bimodal high-density polyethylene through optimization of the operating parameters of the reactors and catalyst design.

Effects of annealing and swelling to initial plastic deformation of polyethylene probed by nonlinear ultrasonic guided waves

“…A higher penetration rate was observed for CO samples, possibly due to its lower crystal content resulting in greater vulnerability to swelling [48]. And the stability presented by the BM can also be explained by the barrier effect of tie chains to diffusion of low molecular weight molecules [49]. These results highlight the potential of using the ultrasonic parameter to monitor diffusion of low molecular weight components over exposure time in polyethylene parts in use.…”

Demystifying the two-sided role of inorganic halides in the structure and performance of Ziegler–Natta catalysts

“…During the chlorination phase (with EASC), the ethoxide groups of Mg(OEt) 2 are replaced by chlorine groups coming from EASC, resulting in a change in the crystal structure of the support from Mg(OEt) 2 into MgCl 2 . 8,17,42 It can be justified by investigating Fig. 3, where the crystal structure of Mg(OEt) 2 completely changed to MgCl 2 in all the synthesized catalysts.…”

Chlorination of Mg(OEt)2 with Halocarbons: A Promising Approach for Eliminating Chlorine-Containing Activators from Ziegler–Nattas’ Recipes

“…While different types of donors, promotors, and so forth are frequently added to the base formulation, MgCl 2 and TiCl 4 can be considered the backbone of all ZNCs’ recipes. ,− In addition, MgCl 2 can be used as a starting material or produced in situ during ZNC synthetic approaches. − The second choice is strongly preferable, especially when a morphology-less catalyst is targeted. Most slurry-based polymerization technologies use Mg­(OEt) 2 -based ZNCs to produce their products due to their low price and ease of handling. − …”