| Abstract: | The stepwise creep in polyethylenes of the trademarked pipes Hostalen 4731b and Dowlex 2388 is compared to that of standard HDPE and LDPE. With the aim to study the deformation of the interlamellar macromolecules, a temperature of 100°C is chosen. At this temperature, the destruction of the interlamellar aggregates results in their easy deformation with the preservation of the integrity of the main crystalline framework. The process is performed under a light load, as a result of which there is deformation relaxation to some limiting value, and then the loading is repeated. The ordering of the lamellar structuring in the annealed samples leads to a sharp decrease in deformability of the interlamellar molecules, unlike what is observed in quenched samples. The shortening of samples is established after stepwise unloading similar to the loading. The Dowlex 2388 copolymer exhibits a sharp increase in tear resistance at 115°C accompanied by a local rise in the orientation stretching of the interlamellar molecules, whose subsequent breakage leads to a significant increase in the slot width after tearing at 115 ± 5°C, i.e., at exactly the maximum resistance. |
