Degradation of pre-aged polymers exposed to simulated recycling: Properties and thermal stability

Accelerated thermal and photo-aging of four homopolymers, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and high-impact polystyrene (HIPS), was performed and the impact of subsequent reprocessing conditions on their properties studied. Polymer samples oven-age...

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Bibliographic Details
Published in:	Polymer degradation and stability Vol. 91; no. 6; pp. 1226 - 1232
Main Authors:	Luzuriaga, Sharbel, Kovářová, Jana, Fortelný, Ivan
Format:	Journal Article
Language:	English
Published:	Oxford Elsevier Ltd 01-06-2006 Elsevier Science
Subjects:	Accelerated weathering Ageing Applied sciences Exact sciences and technology Physical properties Polymer industry, paints, wood Polyolefins Properties and testing Re-stabilization Reprocessing Simulated recycling Styrenics Technology of polymers Styrenics Re-stabilization Accelerated weathering Simulated recycling Reprocessing Polyolefins Thermal ageing High density ethylene polymer Thermooxidative degradation Thermal stability Low density ethylene polymer High impact styrene polymer Impact strength Reaction mechanism Olefin polymer Recycling Exposure time Photochemical degradation Propylene polymer Mechanical properties Crosslinking Experimental study Tensile strength Thermal properties Artificial ageing Rheological properties
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Summary:	Accelerated thermal and photo-aging of four homopolymers, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and high-impact polystyrene (HIPS), was performed and the impact of subsequent reprocessing conditions on their properties studied. Polymer samples oven-aged at 100 °C for varying periods of time or UV irradiated in a Weather-o-meter (WOM) at λ = 340 nm were reprocessed in a Brabender plasticorder at 190 °C/60 rpm for 10 min. Chemical changes and the evolution of rheological and mechanical properties accompanying the gradual degradation of the individual polymers were monitored and evaluated (DSC, FTIR, colorimetric method, MFI, tensile impact strength). LDPE and HIPS were found to be more susceptible to thermo-oxidation than HDPE and PP, whereas HDPE and PP were affected to a greater extent by UV exposure; the crucial role here is being played by the stabilization of the studied resins. In HDPE the scission and crosslinking reactions competed both in thermo-and photo-degradation. In the case of LDPE, scission prevailed over branching during thermo-oxidation, whereas photo-oxidation of the same sample led predominantly to crosslinking. Abrupt deterioration of the LDPE rheological properties after one week of thermal exposure was suppressed by re-stabilization. The scission reaction was also predominant for PP during thermo-oxidation, and it took place even faster during UV exposure. In the case of HIPS a slight photo-degradation of PS matrix is accompanied by simultaneous crosslinking of the polybutadiene component.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0141-3910 1873-2321
DOI:	10.1016/j.polymdegradstab.2005.09.004