Effect of structural parameters on RCP in polyethylene


Fracture - RCP # 2004 Milan

Changing the catalyst composition, it allowed us to alter placement of comonomer from lower to higher polymer molecular weight fractions together with a certain reduction of molecular weight distribution (MWD). Using this catalyst several polymer samples differing in level of branching, in comonomer unit placement and in MWD broadness were prepared on plant facility. These polymer samples were then used to study relationship between material structure and critical pressure below which RCP does not occur. Several analytical methods were employed in the polymer samples evaluation (TREF, SIS/DSC, IR) and results of these techniques were correlated with polymer performance characteristics obtained from S4 test, notch pipe test (NPT) and modified Charpy test (PSI - plane stress impact). The correlation between the fracture and structural parameters has been found. Further more, the decisive structure of the polymer matrix for high resistance against RCP has been proposed.

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