Rheological and thermal degradation behavior of polypropylene/low-density polyethylene blends under successive...

Area of Science:

• Polymer Science
• Materials Science
• Chemical Engineering

Background:

• Repeated extrusion recycling of polymers like polypropylene (PP) and low-density polyethylene (LDPE) can alter their properties.
• Understanding degradation mechanisms is crucial for optimizing recycling processes and material performance.

Purpose of the Study:

• To investigate the molecular, thermal, viscoelastic, and morphological changes in PP, LDPE, and their blends during multiple extrusion recycling cycles.
• To determine how blend composition influences the degradation behavior and recyclability of PP/LDPE systems.

Main Methods:

• Melt Flow Index (MFI)
• Gel Permeation Chromatography (GPC)
• Differential Scanning Calorimetry (DSC)
• Thermogravimetric Analysis (TGA)
• Oxidation Induction Time (OIT)
• Dynamic Rheological Measurements
• Scanning Electron Microscopy (SEM)

Main Results:

• PP degraded via chain scission (44% MFI increase), while LDPE showed branching/crosslinking (35% MFI decrease).
• The PP90/PE10 blend degraded most severely due to partial miscibility and interfacial stress accelerating PP degradation.
• The PP80/PE20 blend exhibited greater stability, attributed to larger LDPE domains improving stress distribution.

Conclusions:

• PP and LDPE exhibit distinct degradation pathways during recycling.
• Blend composition and interfacial morphology critically influence the recyclability and rheological properties of PP/LDPE systems.
• Optimizing blend ratios is key to enhancing the performance of recycled PP/LDPE materials.