Polyethylene loss of ductility during oxidation: Effect of initial molar mass distribution. (March 2018)

• Record Type: Journal Article
• Authors: Reano, Armando F.; Guinault, Alain; Richaud, Emmanuel; Fayolle, Bruno
• Is Part Of: Polymer degradation and stability. Volume 149(2018)
• Page Start: 78
• Page End: 84
• Publication Date: 2018-03
• Subjects: Polyethylene -- Oxidation -- Loss of ductility -- Polydispersity -- Chemicrystallization; Polymers -- Deterioration -- Periodicals; Stabilizing agents -- Periodicals; Polymères -- Dégradation -- Périodiques; Stabilisants -- Périodiques; 668.9
• DOI: 10.1016/j.polymdegradstab.2018.01.021
• Languages: English
• ISSNs: 0141-3910

Abstract

Abstract: This paper reports a study of thermal oxidation induced embrittlement in several polyethylene grades differing mainly by the broadness of the molar mass distribution (ranging for lower than 3 to more than 30). Thermal oxidation was monitored at macromolecular scale (Gel Permeation Chromatography, Differential Scanning Calorimetry) and macroscopic scale (tensile tests). As expected, the samples undergo predominant chain scission and plastic deformation is suppressed below a critical molar mass value (M'C ). Even though this latter was previously reported to be independent of the initial weight average molar mass, it is shown here that it depends on initial polydispersity index. Samples were also shown to undergo chemicrystallization, i.e. that segments released by chain scissions migrate into the crystalline phase with a yield increasing with initial polydispersity index. Finally, the main novelty of this work is to evidence that the previously proposed end-of-life criteria at macromolecular level linked to loss of ductility (critical molar mass, crystallization yield) depend on the initial polydispersity index. Highlights: Thermal oxidation of polyethylene differing by their dispersity. Degradation by chain scission. Loss of ductility occurs when molar mass is below a critical value. Effect of dispersity on end of life criteria: critical molar mass and chemicrystallization yield.