Recycling rigid polypropylene from mixed waste: Does the origin affect mechanical recyclate quality?

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Low plastic recycling rates and high incineration of non-packaging plastic waste in Austria necessitate improved recycling strategies.
• Mixed waste streams contain significant amounts of recyclable plastics, particularly rigid polypropylene (PP), which is often incinerated.
• Existing research predominantly focuses on packaging plastics, leaving a gap in understanding the recyclability of non-packaging plastics from mixed waste.

Purpose of the Study:

• To investigate the feasibility of recycling rigid polypropylene (PP) from mixed waste in Austria.
• To evaluate the quality and properties of recycled PP derived from non-packaging plastic waste.
• To assess the potential contribution of recycling mixed waste plastics to circular economy objectives.

Main Methods:

• Mechanical pre-processing of mixed waste plastics, including washing and sink-float separation.
• Polymer processing techniques to transform sorted plastics into recyclates.
• Comprehensive evaluation of recyclate properties: tensile (impact), thermal, morphological, and rheological.

Main Results:

• Rigid PP recovered from mixed waste exhibits dirt content comparable to separately collected waste.
• Homogeneous recyclates with minor polyethylene impurities were successfully produced.
• The quality of the produced recyclates, particularly elastic modulus and yield stress, is comparable to commercially available PP.

Conclusions:

• Recycling rigid polypropylene (PP) from mixed waste streams in Austria is a viable option.
• The recovered PP demonstrates properties suitable for commercial applications, contributing to plastic circularity.
• Further research is recommended on odour, contaminants, long-term performance, and economic viability.