Mechanical recyclability and biodegradation of biopolymers, biopolymer blends and biocomposite in natural environmental conditions
- Authors: Nomadolo, Nomvuyo Elizabeth
- Date: 2023-12
- Subjects: Polymers , Polymeric composites , Biopolymers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62539 , vital:72822
- Description: The present research aimed at investigating mechanical recyclability and studying the potential biotic and abiotic degradation behaviors of biobased biodegradable polymers in different environmental conditions. The mechanical recyclability tests monitored the effect of multiple reprocessing on the mechanical, thermal, physical, chemical, and morphological properties of poly (butylene adipate-co-terephthalate) (PBAT), poly (butylene succinate) (PBS), poly (lactic acid) (PLA), PBAT-PBS blend, and PBAT-thermoplastic starch (TPS) composite. Low-density polyethylene (LDPE), a conventional non-biodegradable plastic, was also monitored for comparison studies. The mechanical recyclability tests were carried out by eight melt extrusion cycles using twin-screw extrusion and injection molding processing techniques. Tensile testing, impact analysis, melt flow index test (MFI), differential scanning calorimetry (DSC), thermogravimetry (TGA), dynamic mechanical analysis (DMA), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques were employed to monitor the effect mechanical recycling at each melt extrusion cycle. Tensile and impact strength results showed that PBAT and PBAT-TPS biocomposite were mechanical recyclable for at least eight cycles and this was comparable to LDPE recyclability performance. In contrast, neat PBS, PLA, and PBAT-PBS blend were found to be melt extrudable only up to six cycles as the mechanical properties declined with the increase of reprocessing cycles. MFI tests suggest that molecular weight of PBAT and PBAT-TPS were not significantly affected by multiple extrusion cycles while the melt flow properties of PBS, PLA, and PBAT-PBS samples were affected from third cycle. DSC, TGA, and DMA demonstrated that PBAT and PBAT-TPS were more thermo-mechanically stable than PBS, PLA, and PBAT-PBS blend. FTIR spectroscopy results showed that the chemical structure of both PBAT and PBAT-TPS were unaffected by the multiple recycling cycles typically indicated by characteristic peak vibrations bands of C=O and C-O around 1710 cm-1 and 1046-1100 cm-1, respectively. SEM micrographs of PBS, PLA, and PBAT-PBS clearly evidenced the degradation of the biopolymers by severely fractured morphology as a result multiple reprocessing cycle.The rate of aerobic biodegradation for PBAT-PBS and PBAT-PLA blends was examined under controlled home and industrial composting using the CO2 evolution respirometric method. FTIR, DSC, TGA, X-ray diffraction analysis (XRD), and SEM were employed to monitor the changes in the structural, chemical, thermal, and morphological characteristics of the biopolymer blends before and after biodegradation. The biodegradation tests showed that PBAT-PBS and PBAT-PLA blends exhibited higher degradation rates under industrial composting conditions than under home composting conditions. The increased intensity of hydroxyl and carbonyl absorption bands on the FTIR spectra confirmed that the biodegradation process occurred. SEM revealed that there was microbial colony formation and disintegration on the surfaces of the biopolymer blends. Moreover, abiotic degradation results suggested that thermal and hydrolytic conditions influence the degradation process than sunlight exposure. Additionally, aquatic biodegradation results showed that PBAT-PBS blend and PBAT-TPS composite undergo a higher rate of biodegradation as compared to PBAT, PBS, and PLA.The results obtained from this research work conclude that biobased biodegradable polymers can be mechanically recycled, and they are suitable for biological degradation in industrial composting, home composting and marine environment. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
- Authors: Nomadolo, Nomvuyo Elizabeth
- Date: 2023-12
- Subjects: Polymers , Polymeric composites , Biopolymers
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/62539 , vital:72822
- Description: The present research aimed at investigating mechanical recyclability and studying the potential biotic and abiotic degradation behaviors of biobased biodegradable polymers in different environmental conditions. The mechanical recyclability tests monitored the effect of multiple reprocessing on the mechanical, thermal, physical, chemical, and morphological properties of poly (butylene adipate-co-terephthalate) (PBAT), poly (butylene succinate) (PBS), poly (lactic acid) (PLA), PBAT-PBS blend, and PBAT-thermoplastic starch (TPS) composite. Low-density polyethylene (LDPE), a conventional non-biodegradable plastic, was also monitored for comparison studies. The mechanical recyclability tests were carried out by eight melt extrusion cycles using twin-screw extrusion and injection molding processing techniques. Tensile testing, impact analysis, melt flow index test (MFI), differential scanning calorimetry (DSC), thermogravimetry (TGA), dynamic mechanical analysis (DMA), Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques were employed to monitor the effect mechanical recycling at each melt extrusion cycle. Tensile and impact strength results showed that PBAT and PBAT-TPS biocomposite were mechanical recyclable for at least eight cycles and this was comparable to LDPE recyclability performance. In contrast, neat PBS, PLA, and PBAT-PBS blend were found to be melt extrudable only up to six cycles as the mechanical properties declined with the increase of reprocessing cycles. MFI tests suggest that molecular weight of PBAT and PBAT-TPS were not significantly affected by multiple extrusion cycles while the melt flow properties of PBS, PLA, and PBAT-PBS samples were affected from third cycle. DSC, TGA, and DMA demonstrated that PBAT and PBAT-TPS were more thermo-mechanically stable than PBS, PLA, and PBAT-PBS blend. FTIR spectroscopy results showed that the chemical structure of both PBAT and PBAT-TPS were unaffected by the multiple recycling cycles typically indicated by characteristic peak vibrations bands of C=O and C-O around 1710 cm-1 and 1046-1100 cm-1, respectively. SEM micrographs of PBS, PLA, and PBAT-PBS clearly evidenced the degradation of the biopolymers by severely fractured morphology as a result multiple reprocessing cycle.The rate of aerobic biodegradation for PBAT-PBS and PBAT-PLA blends was examined under controlled home and industrial composting using the CO2 evolution respirometric method. FTIR, DSC, TGA, X-ray diffraction analysis (XRD), and SEM were employed to monitor the changes in the structural, chemical, thermal, and morphological characteristics of the biopolymer blends before and after biodegradation. The biodegradation tests showed that PBAT-PBS and PBAT-PLA blends exhibited higher degradation rates under industrial composting conditions than under home composting conditions. The increased intensity of hydroxyl and carbonyl absorption bands on the FTIR spectra confirmed that the biodegradation process occurred. SEM revealed that there was microbial colony formation and disintegration on the surfaces of the biopolymer blends. Moreover, abiotic degradation results suggested that thermal and hydrolytic conditions influence the degradation process than sunlight exposure. Additionally, aquatic biodegradation results showed that PBAT-PBS blend and PBAT-TPS composite undergo a higher rate of biodegradation as compared to PBAT, PBS, and PLA.The results obtained from this research work conclude that biobased biodegradable polymers can be mechanically recycled, and they are suitable for biological degradation in industrial composting, home composting and marine environment. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-12
An investigation into the use of a ceramifiable Ethylene Vinyl Acetate (EVA) co-polymer formulation to aid flame retardency in electrical cables
- Authors: Bambalaza, Sonwabo Elvis
- Date: 2014
- Subjects: Vinyl acetate , Polymeric composites , Inorganic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10433 , http://hdl.handle.net/10948/d1020159
- Description: The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
- Full Text:
- Date Issued: 2014
- Authors: Bambalaza, Sonwabo Elvis
- Date: 2014
- Subjects: Vinyl acetate , Polymeric composites , Inorganic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10433 , http://hdl.handle.net/10948/d1020159
- Description: The concept of a unique ceramifiable Ethylene vinyl acetate (EVA) based polymer composite was based on the incorporation of inorganic compounds such as aluminium hydroxide, calcium carbonate, muscovite mica, and calcined kaolinite within a 95 percent EVA/ 5 percent Polydimethylsiloxane (PDMS) polymer matrix such tha t upon heating to elevated temperatures of about 1000 oC, a solid end-product with ceramic-like properties would be formed. The ceramifiable EVA based polymer composite was developed to be used as electric cable insulation or sheath as the formation of a ceramic based material at elevated temperatures would provide flame retardant properties during fire situations. The flame retardant properties at elevated temperatures would ensure that the insulation remains at such temperatures due to some of the properties of the resultant ceramic such as reasonably high flexural strength, high thermal stability, non-reactivity and high melting point. During a fire this would ensure that flames would not be propagated along the length of the cable and also protect the underlying conducting wires from being exposed to the high temperatures of the fire. Its application as a cable insulation also required that the material functions as a cable insulator under ambient temperature conditions where the ceramifiable polymer composite should retain certain polymer properties such as the post-cure tensile strength (MPa), degree of polymer elongation (percent), thermal expansion, thermal slacking, limited oxygen index and electrical insulation. This study made use of a composite experimental design approach that would allow for the optimization of the amounts of the additives in the ceramifiable polymer composite giving both the desired mechanical properties of the material under normal operating temperatures as a polymer and also as a ceramic once exposed to elevated temperatures. The optimization of additives used in the ceramifiable polymer composite was done by using a D-optimal mixture design of experiments (DoE) which was analyzed by multiple linear regression.
- Full Text:
- Date Issued: 2014
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