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Structure-property relationships in recycled agricultural netting
Thesis (MSc)--Stellenbosch University, 2025.
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613983789285376 |
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| access_status_str | Open Access |
| author | Lehabe, Karabo Petrus |
| author2 | Matthews, Megan |
| author_browse | Lehabe, Karabo Petrus Matthews, Megan |
| author_facet | Matthews, Megan Lehabe, Karabo Petrus |
| author_sort | Lehabe, Karabo Petrus |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134673 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:44:49.127Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134673 Structure-property relationships in recycled agricultural netting Lehabe, Karabo Petrus Matthews, Megan Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Polyethylene Agricultural wastes Plastics in agriculture Polymers -- Testing Thesis (MSc)--Stellenbosch University, 2025. Lehabe, K. P. 2025. Structure-property relationships in recycled agricultural netting. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/a214bcdf-9b31-4e1d-9948-0ac00acd6fc0 ENGLISH ABSTRACT: Polyethylene (PE) is the largest produced plastic material globally due to its excellent chemical properties and good processibility, however these properties are the source of its longevity in the environment and therefore the cause of its pollution problem. High density polyethylene (HDPE) is a popular polymer for agricultural permeable covers due to its high resistance to environmental degradation. The average lifecycle of a permeable cover ranges from 5 – 15 years, after which they are dumped, incinerated or kept on site. According to new regulations on extended producer responsibility (EPR), net producers and raw material suppliers are responsible for management of the net waste after completion of its lifecycle. To facilitate circular economy practices within the agricultural industry these nets should be recycled into a second lifecycle. Modern net molecular weight (MW) compositions have evolved to use bimodal HDPE which contains two molecular weight distributions (MWDs) providing the net structure with added toughness and environmental stress-crack resistance (ESCR). This project successfully characterized HDPE samples with unimodal and bimodal MWDs. The samples incorporated varying ratios of unimodal and bimodal HDPE components and characterization was performed to determine if blending HDPE of different MW would be a valuable way to recycle the agricultural nets. Pesticide residue analysis was performed to evaluate the safety of re-melting the nets during the recycling process. Fourier-transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR) spectroscopy were used to explore the chemical composition and morphology of the samples. Differential scanning calorimetry (DSC), melt flow index (MFI) and small-amplitude oscillatory shear (SAOS) were employed to investigate thermal, rheological and processing properties. The absence of any volatilizable compounds that would pose a safety hazard for re-melting during the recycling process was confirmed using thermogravimetric analysis (TGA), while solution NMR and LC-tandem mass spectrometry (LC-MS/MS) confirmed low-level agrichemical residues. These properties were used as an indication of the mechanical performance and processibility of the samples. Nets with longer exposure periods in the environment exhibited low levels of degradation. Virgin bimodal HDPE (F3) was reported to have a low melt strength, however, blending of F3 and the agricultural nets improved the overall melt strength of the samples. Cross-over modulus was a key parameter in determining the melt strength for making net filaments. The blends exhibited shear thinning, a key aspect in polymer processing to enable efficient polymer processing and applications. LC–MS/MS results indicated the presence of Chlorfenapyr in trace amounts of 0.0093 and 0.0105 parts per million (ppm) in the 2006 and 2017 nets. Despite the low concentrations it is important that the net producers are aware of this because Chlorfenapyr was reported to pose a health risk by the World Health Organization (WHO) even at low concentrations. This will limit applications for the potential second lifecycle of these nets. The structure-property relationships of the recycled material confirmed the safety and performance of the material without compromising its integrity. This project can provide a foundation for a circular economy model in the agricultural context. AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar. Masters 2025-12-23T06:52:16Z 2025-12-23T06:52:16Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134673 en Stellenbosch University xvi, 86 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Polyethylene Agricultural wastes Plastics in agriculture Polymers -- Testing Lehabe, Karabo Petrus Structure-property relationships in recycled agricultural netting |
| title | Structure-property relationships in recycled agricultural netting |
| title_full | Structure-property relationships in recycled agricultural netting |
| title_fullStr | Structure-property relationships in recycled agricultural netting |
| title_full_unstemmed | Structure-property relationships in recycled agricultural netting |
| title_short | Structure-property relationships in recycled agricultural netting |
| title_sort | structure property relationships in recycled agricultural netting |
| topic | Polyethylene Agricultural wastes Plastics in agriculture Polymers -- Testing |
| url | https://scholar.sun.ac.za/handle/10019.1/134673 |
| work_keys_str_mv | AT lehabekarabopetrus structurepropertyrelationshipsinrecycledagriculturalnetting |