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Evaluation of WPC properties made with different wood types, additives and processing techniques
Thesis (MScFor)--Stellenbosch University, 2025.
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Stellenbosch : Stellenbosch University
2026
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| _version_ | 1867613854201020416 |
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| access_status_str | Open Access |
| author | Mofokeng, Mohau Alphios |
| author2 | Meincken, Martina |
| author_browse | Meincken, Martina Mofokeng, Mohau Alphios |
| author_facet | Meincken, Martina Mofokeng, Mohau Alphios |
| author_sort | Mofokeng, Mohau Alphios |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScFor)--Stellenbosch University, 2025. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/134710 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:42:44.343Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/134710 Evaluation of WPC properties made with different wood types, additives and processing techniques Mofokeng, Mohau Alphios Meincken, Martina Van Helden, Pieter Stellenbosch University. Faculty of AgriSciences. Dept. of Forest & Wood Science. Plastic-impregnated wood Composite materials -- Properties White oak Wattles (Plants) Polyethylene plants Thesis (MScFor)--Stellenbosch University, 2025. Mofokeng, M. A. 2025. Evaluation of WPC properties made with different wood types, additives and processing techniques. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/454d5bfe-21ea-4a26-ac48-292fc9d4b0bc ENGLISH ABSTRACT: Wood plastic composites (WPCs) were developed from the entire biomass of invasive trees (woody and non-woody parts) and white oak (wood only) and virgin high-density polyethylene. The primary aim of this study was to compare properties of WPCs made with model wood (white oak) and Port Jackson (Acacia saligna) wood and entire Port Jackson trees, by evaluating the effect of different wood fiber types and their extractives on bond formation, durability, and the mechanical properties of WPCs. Port Jackson is an invasive tree species and regarded as waste material and the subsequent product development adds value to it, while simultaneously reducing the waste stream. A. saligna was salvaged from clearing operations and was used as received without any prior processing to minimise associated processing costs. Virgin high density polyethylene (HDPE) was used as the matrix to make the WPC samples with the addition of maleic anhydride polyethylene (MAPE) as additive to improve surface interaction between the polymer and the wood particles. The WPC samples were produced with a biomass content of 50:50 wt%, with a particle size <0.5mm and pressed for 30min and extruded at 160°C, to obtain WPC boards and strips for evaluations of water absorption (WA), thickness swelling (TS), tensile and flexural strength. The specific particle size was kept constant, because the study is not based on evaluating the effect of particle size in WPC performance. The WPC samples that included non-woody parts exhibited lower physical strength compared to WPCs made solely from wood. This is likely due to processing conditions, as the non-woody parts contain more extractives and hemicelluloses, which degrade faster than those in woody parts. The volatilization and removal of these extractives create voids within the composite, leading to diminished physical properties. Conversely, WPC samples with MAPE (maleic anhydride grafted polyethylene) demonstrated enhanced physical and mechanical properties. MAPE acts to improve the bonding between the polar wood fibers and the non-polar polymer matrix, enabling more efficient transfer of stress from the polymer to the wood fibers, thereby strengthening the composite. The 24 h WA and TS results suggest that the processing technique used to prepare the samples, namely, extrusion or compression molding, has an effect on the water absorption of the WPC, especially after weathering, which has a negative effect on both WA and TS, but more pronounced in compression molded samples. The presence of MAPE leads to an improved interfacial interaction between the wood fibers and polymer matrix, which resulted in low water uptake, and therefore less TS. Minimal fungal (mold) growth was observed on all WPC samples tested and the most significant growth was observed on the WPC samples exposed to Penicillium pinalocum. Resistance to fungal growths on other fungus, namely, Black yeast, Aspergilus sp.(bees), Aspergillus sp. (blueberry flowers), Trichoderma Vvirense can be assigned to the extractives contained in the woody and non-woody parts of the biomass. Although the presence of anti-fungal compounds in leaves and bark (non-woody) parts of A. saligna and other anti-fungal compounds on the woody parts of the biomass (PJW and oak) in the WPC formulation did not entirely prevent the growth of molds, active growth was significantly slowed down. AFRIKAANSE OPSOMMING: Die HPK-monsters is vervaardig met ’n biomassa-inhoud van 50:50 gewigspersentasie, met ’n deeltjiegrootte van en stroke te verkry vir die evaluering van waterabsorpsie (WA), dikteswelling (DS), treksterkte en buigsterkte. Die spesifieke deeltjiegrootte is konstant gehou, aangesien die studie nie gebaseer is op die evaluering van deeltjiegrootte se invloed op HPK-prestasie nie. Hout-plastiek komposiete (HPK’s) is ontwikkel uit die volledige biomassa van indringerspesies (houtagtige en nie-houtagtige dele) en wit eikehout (slegs hout), saam met ongerepte hoëdigtheidpoliëtileen (HDPE). Die hoofddoel van hierdie studie was om die eienskappe van HPK’s wat gemaak is met modelhout (wit eikehout) en Port Jackson (Acacia saligna) hout, sowel as volledige Port Jacksonbome, te vergelyk deur die invloed van verskillende houtveselsoorte en hul uittreksels op bindingsvorming, duursaamheid en meganiese eienskappe van HPK’s te evalueer. Port Jackson is ’n indringerboomspesie en word as afvalmateriaal beskou; die daaropvolgende produkontwikkeling voeg waarde daaraan toe, terwyl dit terselfdertyd die afvalstroom verminder. A. saligna is afkomstig van uitroeiingsbedrywighede en is gebruik soos ontvang, sonder enige voorafverwerking, om die gepaardgaande verwerkingskoste te verminder. Ongerepte hoëdigtheidpoliëtileen (HDPE) is as matriks gebruik om die HPK-monsters te vervaardig, met die byvoeging van maleïenanhidried-poliëtileen (MAPE) as toevoegmiddel om die oppervlakinteraksie tussen die polimeer en die houtdeeltjies te verbeter. Die HPK-monsters wat nie-houtagtige dele ingesluit het, het laer fisiese sterkte getoon in vergelyking met HPK’s wat slegs van hout gemaak is. Dit is waarskynlik as gevolg van die verwerkingsomstandighede, aangesien die nie-houtagtige dele meer uittreksels en hemiselulose bevat wat vinniger afbreek as dié in die houtagtige dele. Die verdamping en verwydering van hierdie uittreksels skep holtes binne die komposiet, wat lei tot verminderde fisiese eienskappe. Daarenteen het HPK-monsters met MAPE (maleïenanhidried-gekoppelde poliëtileen) verbeterde fisiese en meganiese eienskappe getoon. MAPE verbeter die binding tussen die polêre houtvesels en die nie-polêre polimeermatriks, wat meer doeltreffende spanningsoordrag van die polimeer na die houtvesels moontlik maak en sodoende die komposiet versterk. Die 24-uur WA- en DS-resultate dui daarop dat die verwerkingstegniek wat gebruik is om die monsters voor te berei, naamlik ekstrusie of kompressievorming, ’n invloed het op die waterabsorpsie van die HPK, veral na verwering. Verwering het ’n negatiewe effek op beide WA en DS, wat meer uitgesproke is in kompressievormde monsters. Die teenwoordigheid van MAPE het gelei tot verbeterde grensvlakinteraksie tussen die houtvesels en die polimeermatriks, wat tot laer wateropname en gevolglik minder DS gelei het. Minimale swamgroei (skimmel) is op al die getoetsde HPK-monsters waargeneem, met die mees betekenisvolle groei op die monsters wat blootgestel is aan Penicillium pinalocum. Weerstand teen ander swamme — naamlik swart gis, Aspergillus sp. (bye), Aspergillus sp. (bloubessieblomme), en Trichoderma virense — kan toegeskryf word aan die uittreksels wat in die houtagtige en nie-houtagtige dele van die biomassa voorkom. Alhoewel die teenwoordigheid van antimisieliese verbindings in die blare en bas (nie-houtagtige dele) van A. saligna en ander antimisieliese verbindings in die houtagtige dele van die biomassa (PJW en eikehout) in die HPK-formulering nie die groei van skimmels heeltemal voorkom het nie, is aktiewe groei beduidend vertraag. Masters 2026-01-05T07:01:43Z 2026-01-05T07:01:43Z 2025-12 Thesis https://scholar.sun.ac.za/handle/10019.1/134710 Stellenbosch University vi, 69 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Plastic-impregnated wood Composite materials -- Properties White oak Wattles (Plants) Polyethylene plants Mofokeng, Mohau Alphios Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title | Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title_full | Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title_fullStr | Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title_full_unstemmed | Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title_short | Evaluation of WPC properties made with different wood types, additives and processing techniques |
| title_sort | evaluation of wpc properties made with different wood types additives and processing techniques |
| topic | Plastic-impregnated wood Composite materials -- Properties White oak Wattles (Plants) Polyethylene plants |
| url | https://scholar.sun.ac.za/handle/10019.1/134710 |
| work_keys_str_mv | AT mofokengmohaualphios evaluationofwpcpropertiesmadewithdifferentwoodtypesadditivesandprocessingtechniques |