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1.
ACS Appl Polym Mater ; 6(3): 2031-2040, 2024 Feb 09.
Article in English | MEDLINE | ID: mdl-38357437

ABSTRACT

Fluorophores displaying concentration-dependent luminescence are becoming increasingly valuable in stress-sensing, tagging, and dyeing applications, including the quantification of recycled content in plastic packaging. In this work, we investigate the effects of the polymer matrix, dye structure, and crystallinity on aggregation-induced enhanced emission (AIEE). We demonstrate that the aggregation threshold required for successful quantification can be adjusted through modulation of guest-host (dye-polymer) interactions and monitored using an array of fluorescence characterization. Modification of guest-host interactions is realized through choice of host, change of guest, and tuning of the crystallinity of the host system. Increasing the number of guest-host interactions and solubility between guest and host, loosely predicted through the calculation of the solubility parameter, increases the aggregation threshold relative to other low-polarity and low-interacting systems. We demonstrate that issues, such as loading level and cost, associated with high aggregation thresholds, can be circumvented by increasing system crystallinity, improving spectral intensities, and subsequent quantification. These insights explore the fundamental understanding of supramolecular interactions that govern dye-polymer systems.

2.
ACS Sustain Chem Eng ; 10(38): 12659-12669, 2022 Sep 26.
Article in English | MEDLINE | ID: mdl-36189110

ABSTRACT

The linearity of the plastics economy is wasteful and polluting. To encourage recycling and decrease diversion to landfill, new legislation within the EU and UK will tax single-use plastic products made with less than 30% recycled plastic. At present, quantitative determination of recycled content is elusive and existing methods are inconsistent. We present a fluorescence-based analytical technique to determine recycled content in plastic and (single use) packaging. Bathochromic shifts resulting from aggregation of the fluorescent brightener 4,4'-bis(2-benzoxazolyl) stilbene (BBS) in three commodity plastics [high-density polyethylene, polypropylene, and poly(ethylene terephthalate)] at loadings ≤0.5 wt % were used to systematically quantify simulated recycled contents as low as 10 wt %. Linear correlations were found between recycled content and three fluorescence-based properties: emission, lifetime, and resulting color. We demonstrate how this multi-branched verification system is completely independent of sample dimensions and processing conditions, has a negligible effect on polymer properties, and is inexpensive and highly compatible with existing recycling infrastructure.

3.
Macromol Rapid Commun ; 42(3): e2000415, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33000883

ABSTRACT

The current global plastics economy is highly linear, with the exceptional performance and low carbon footprint of polymeric materials at odds with dramatic increases in plastic waste. Transitioning to a circular economy that retains plastic in its highest value condition is essential to reduce environmental impacts, promoting reduction, reuse, and recycling. Mechanical recycling is an essential tool in an environmentally and economically sustainable economy of plastics, but current mechanical recycling processes are limited by cost, degradation of mechanical properties, and inconsistent quality products. This review covers the current methods and challenges for the mechanical recycling of the five main packaging plastics: poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) through the lens of a circular economy. Their reprocessing induced degradation mechanisms are introduced and strategies to improve their recycling are discussed. Additionally, this review briefly examines approaches to improve polymer blending in mixed plastic waste streams and applications of lower quality recyclate.


Subject(s)
Plastics , Recycling , Polyethylene Terephthalates , Polymers , Product Packaging
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