Plastic Pipes Conference Association # 2006 Washington DC
Sindelar, Nezbedova, Buran
The influence of processing conditions on molecular structure and microstructure of highdensity polyethylene pipe material has been studied. By modifying the segment arrangement and package of additives, conditions during pelletising in the extruder have been changed. Structural analyses obtained by gel permeation chromatography (GPC), infra-red spectroscopy (FTIR) and elution fractionation (TREF) were correlated with mechanical characteristics obtained from full notch creep (FNCT) test and modified plane strain impact Charpy tests (PSI). The structural factors underlying this correlation are discussed. A correlation between the structural parameters and fracture processes has been found. Specifically, the ability to minimise the energy input in the course of polymer powder processing appears to provide good resistance to slow crack growth, whereas the degree of crystallinity and lamellar thickness play a decisive role in the rapid crack propagation process.
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