Qualitative and quantitative contaminants assessment in recycled pellets from post‐consumer plastic waste by means of spectroscopic and thermal characterization

Abstract

The complexity of any plastic recycling initiative lies in the heterogeneous nature of the post‐consumer commingled plastic waste stream: recycling treatments are challenging without prior reliable sorting. A suitable identification system should be able to recognize different plastics and blends. Nowadays, the main technique used as quality control in plastic waste sorting centers is differential scanning calorimetry, whose result can be purely qualitative or semi‐quantitative, since only the crystalline fraction is evaluated. Moreover, the time required for data acquisition is relatively long. Infrared spectroscopy is an alternative, faster technique extensively used in applied research, but not widely utilized in industry. In this work, the cross‐use of infrared spectroscopy and calorimetry is tested in a real, practical case: the quality control of recycled pellets (namely composed of polyolefins only), which represent the output of a commingled plastic recycling plant and are used as secondary raw materials for different applications. Appropriate infrared spectroscopy calibration curves were built to allow the quantitative analysis with respect to the most common polymers found in the commingled plastic waste stream; the composition and contaminants in the recycled pellets were thereby determined and tracked through different production batches through the cross‐use of the two techniques outlined above.

A comparison between laboratory‐scale and large‐scale high‐intensity washing of flexible polyethylene packaging waste

“…All the samples exhibited a main endotherm peak at 125°C, with a shoulder at 111°C and a small peak at 161°C. The main peak with a shoulder was related to the different grades of PE, T p1 to LDPE and T p2 to medium‐density PE and HDPE, and the small peak T p3 was attributed to PP 31–33 . There were no significant differences in thermal properties of compounded pellets and IM samples as shown in Figure 2.…”

Elevating Recycling Standards: Global Requirements for Plastic Traceability and Quality Testing

“…Further enhancement is achieved by evaluating molecular weight distribution and composition using Size-Exclusion Chromatography and mass spectrometric methodologies. Cozzarini et al (2023) [48] explore the combined use of infrared spectroscopy and calorimetry in real-world scenarios, specifically for the quality control of recycled pellets composed solely of polyolefins. Calibration curves were developed for infrared spectroscopy to enable quantitative analysis of common polymers in the plastic waste stream.…”

Correlation of structure, rheological, thermal, mechanical, and optical properties in Low Density Polyethylene/Linear Low Density Polyethylene blends in the presence of recycled Low Density Polyethylene and Linear Low Density Polyethylene

“…1 Disposing of such plastics creates the demand for production, leading to an increase in raw fossil fuel consumption and various environmental issues. 4,[8][9][10][11] These environmental and economic concerns are the main reason for the increased public interest in recycling plastic materials and shifting to a comprehensive approach that transforms the linear economy into a circular one. Collecting, recycling, and repurposing waste material in other production processes creates a circular economy.…”

“…Depending on the recycling policies of each country, post-consumer waste is either collected separately or along with other waste materials, which could lead to the mixing of both high and low-quality materials. 10 Understanding the composition of this waste is not an easy task since it could contain a mixture of various polymers, not to mention the possible contaminations, including organic components (liquid or solid) or non-polymeric components such as paper and metal. It is evident that recycling postconsumer waste is more challenging compared to postindustrial waste and requires more steps.…”