Effect of UV-aging on the mechanical and fracture behavior of low density polyethylene

• Published in: Polymer degradation and stability Vol. 180; p. 109185
• Main Authors: Rodriguez, A.K., Mansoor, B., Ayoub, G., Colin, X., Benzerga, A.A.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.10.2020; Elsevier BV; Elsevier
• Subjects: Cavitation; Chain scission; cleavage (chemistry); Cracking (fracturing); Cracks; Crosslinking; Crystallization; Deformation; degradation; Density; Effects; Engineering Sciences; Low density polyethylenes; Materials; Mechanical behavior; Mechanical damage; Mechanical tests; Oxidation; Photo-oxidation; Plastic deformation; Polyethylene; Polyethylene films; Radiation dosage; Strengthening; Studies; Ultraviolet radiation; Cracks; Mechanical damage; Mechanical behavior; Photo-oxidation; Cavitation
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2020.109185

In polyethylene, a transient, oxidation-induced strengthening is often observed over a narrow range of UV radiation dose. In addition, plastic deformation may not be volume-preserving due to cavitation. Here, we employ a suite of analytical experiments and mechanical testing on pristine and oxidized low-density polyethylene films in order to investigate the transient strengthening behavior as well as the propensity for cavitation to fracture. Emphasis is laid on connecting macroscopically observed behavior with microscopic information involving the competition between multi-scale phenomena: chain scission and cross linking at a fine scale, chemi-crystallization, oxidation-induced cracking and mechanical damage at the meso and coarse scales. The results provide an insight into the role of cavitation in the oxidative embrittlement of semicrystalline polymers. •Chemo-mechanical aspects of oxidative embrittlement are investigated in LDPE using a combination of physico-chemicals and mechanical analyses.•Chemi-crystallization may explain oxidation-induced strengthening over a narrow range of UV radiation dose.•A superficial layer embrittlement model is invoked to rationalize "chemical cracks" by means of a "chemical stress".•Promoted by photo-oxidation induced chain scissions, cavitation is reported for the first time in LDPE.