Predicting the Linear Low-Density Polyethylene Content of Custom Polypropylene Blends and Post-Consumer Materials...

Area of Science:

• Polymer Science
• Materials Science
• Recycling Technology

Background:

• Sustainable economies rely on pure recycled materials.
• Analyzing polyolefin cross-contaminations ensures consistent product quality in recycled plastics.
• Quantifying linear low-density polyethylene (LLDPE) in polypropylene (PP) is essential for effective recycling.

Purpose of the Study:

• To quantify the LLDPE content within PP-dominant materials.
• To evaluate the effectiveness of differential scanning calorimetry (DSC) and rheometry for LLDPE quantification.
• To develop mathematical models for determining LLDPE contamination levels in PP post-consumer recyclates.

Main Methods:

• Differential scanning calorimetry (DSC) for thermal properties.
• Parallel-plate rheometry to assess flow behavior.
• Raman spectroscopy and atomic force microscopy (AFM) for morphological confirmation.

Main Results:

• DSC enthalpies were insufficient for quantifying LLDPE, especially at low concentrations (1-10 wt%).
• Rheometric measurements revealed a deviation from the cross-over point (COP) and zero-shear viscosity correlation with increasing LLDPE content.
• Morphological analysis confirmed LLDPE presence within PP up to 30 wt%.

Conclusions:

• Rheometry, combined with mathematical modeling, offers a viable method for quantifying LLDPE in PP.
• The proposed models can determine low (1-15 wt%) and medium (up to 30 wt%) LLDPE quantities.
• This approach is applicable for assessing LLDPE contamination in PP post-consumer materials, aiding quality control in plastic recycling.