Reprocessability of PHB in extrusion: ATR-FTIR, tensile tests and thermal studies

Rivas, Leonardo Fábio; Casarin, Suzan Aline; Nepomuceno, Neymara C.; Alencar, Marie Isabele; Agnelli, José Augusto Marcondes; Medeiros, Eliton S.; Neto, Alcides de Oliveira Wanderley; Oliveira, Maurício P.; Medeiros, Ana Beatriz de Almeida; Santos, Amélia S.F.

doi:10.1590/0104-1428.2406

Cited by 44 publications

(12 citation statements)

References 62 publications

(85 reference statements)

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“…The shorter polymer chains can form crystals more easily and thus the crystallinity increases. This increase in crystallinity with reprocessing is consistent with the literature [32][33][34][35][36][37][38] and this phenomenon is also known as chemicrystallization process.…”

Section: X-ray Diffractionsupporting

confidence: 91%

Effect of Reprocessing Cycles on the Morphology and Mechanical Properties of a Poly(Propylene)/Poly(Hydroxybutyrate) Blend and its Nanocomposite

Oliveira

Silva

et al. 2021

Mat. Res.

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The use of polymer blends and composites based on fossil-based and bio-based polymers has become an important environmentally protective alternative for common use and disposable plastics applications such as packaging, bottles and trays. The disposal of these more degradable products, however, may also harm the environment and, therefore, recycling these systems becomes relevant. Recycling involves reprocessing which can significantly change the morphology and properties of polymeric products. Therefore, this study deals with the effects of reprocessing cycles on the properties and morphology of blends and nanocomposites based on fossil and bio-based polymers. The systems investigated were: a) neat polypropylene (PP), b) a polypropylene/poly(3-hydroxybutyrate) (PP/PHB) blend and c) PP/PHB/organoclay nanocomposite compatibilized with polypropylene-g-maleic anhydride (PP-g-MA) and erucamide. These materials were submitted to up to seven extrusion cycles in a single screw extruder operating at 60 rpm. Samples were taken after the first, third, fifth and seventh extrusion cycles and their tensile properties and morphology were determined. Scanning electron microscopy indicated that two phases were observed in the blend which showed spherical PHB domains. The addition of clay, PP-g-MA and erucamide improved the adhesion between the nanocomposites components. X-ray diffraction analysis showed that crystallinity tended to increase with the number of reprocessing cycles for all systems investigated up to the fifth cycle and then tended to decrease. A 10% crystallinity increase was observed for neat PP in the fifth cycle. In general, the tensile properties of all systems decreased with reprocessing and the highest losses were observed for the PP/PHB blend after seven processing cycles with 50% and 37% decreases in stress at break and elastic modulus, respectively. Impact strength of the PP matrix and of the PP/PHB blend tended to decrease with reprocessing, except for the nanocomposite which showed a slight increase especially after the seventh processing cycle in which an 18% increase in impact strength was observed.

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Section: X-ray Diffractionsupporting

confidence: 91%

Effect of Reprocessing Cycles on the Morphology and Mechanical Properties of a Poly(Propylene)/Poly(Hydroxybutyrate) Blend and its Nanocomposite

Oliveira

Silva

et al. 2021

Mat. Res.

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“…There are only a few studies on the mechanical and chemical recycling of PHA due to both its high production costs and low amounts in circulation. If a P3HB homopolymer is mechanically recycled by the third extrusion cycle there is a 50% reduction in its tensile strength [98]. The mechanical recycling of PHA copolymers has more potential.…”

Section: Mechanical Recyclingmentioning

confidence: 99%

Recycling of Bioplastics: Routes and Benefits

2020

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Continual reduction of landfill space along with rising CO 2 levels and environmental pollution, are global issues that will only grow with time if not correctly addressed. The lack of proper waste management infrastructure means gloablly commodity plastics are disposed of incorrectly, leading to both an economical loss and environmental destruction. The bioaccumulation of plastics and microplastics can already be seen in marine ecosystems causing a negative impact on all organisms that live there, ultimately microplastics will bioaccumulate in humans. The opportunity exists to replace the majority of petroleum derived plastics with bioplastics (bio-based, biodegradable or both). This, in conjunction with mechanical and chemical recycling is a renewable and sustainable solution that would help mitigate climate change. This review covers the most promising biopolymers PLA, PGA, PHA and bio-versions of conventional petro-plastics bio-PET, bio-PE. The most optimal recycling routes after reuse and mechanical recycling are: alcoholysis, biodegradation, biological recycling, glycolysis and pyrolysis respectively.

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“…The main disadvantage of this scenario is the fact that normally each polymer should be separately treated to obtain a good secondary raw material and that every time a biopolymer is reprocessed there is loss in the physical and mechanical properties of the material [139]. For instance, even though very few studies on pure PHA recycling are available [82], PHA can be recycled but it exhibits a loss in mechanical properties [140]. Similar findings are observed in terms of reduction of tensile strength for PHB after multiple processing cycles, even though its chemical structure and thermal stability remains unchanged [140].…”

mentioning

confidence: 99%

“…For instance, even though very few studies on pure PHA recycling are available [82], PHA can be recycled but it exhibits a loss in mechanical properties [140]. Similar findings are observed in terms of reduction of tensile strength for PHB after multiple processing cycles, even though its chemical structure and thermal stability remains unchanged [140]. Other biocomposites, such as PHBV (a copolymer of PHB and PHV), have the ability to be recycled up to five times without experiencing any physico-mechanical losses [30].…”

mentioning

confidence: 99%

Biodegradation of Wasted Bioplastics in Natural and Industrial Environments: A Review

et al. 2020

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The problems linked to plastic wastes have led to the development of biodegradable plastics. More specifically, biodegradable bioplastics are the polymers that are mineralized into carbon dioxide, methane, water, inorganic compounds, or biomass through the enzymatic action of specific microorganisms. They could, therefore, be a suitable and environmentally friendly substitute to conventional petrochemical plastics. The physico-chemical structure of the biopolymers, the environmental conditions, as well as the microbial populations to which the bioplastics are exposed to are the most influential factors to biodegradation. This process can occur in both natural and industrial environments, in aerobic and anaerobic conditions, with the latter being the least researched. The examined aerobic environments include compost, soil, and some aquatic environments, whereas the anaerobic environments include anaerobic digestion plants and a few aquatic habitats. This review investigates both the extent and the biodegradation rates under different environments and explores the state-of-the-art knowledge of the environmental and biological factors involved in biodegradation. Moreover, the review demonstrates the need for more research on the long-term fate of bioplastics under natural and industrial (engineered) environments. However, bioplastics cannot be considered a panacea when dealing with the elimination of plastic pollution.

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Reprocessability of PHB in extrusion: ATR-FTIR, tensile tests and thermal studies

Cited by 44 publications

References 62 publications

Effect of Reprocessing Cycles on the Morphology and Mechanical Properties of a Poly(Propylene)/Poly(Hydroxybutyrate) Blend and its Nanocomposite

Effect of Reprocessing Cycles on the Morphology and Mechanical Properties of a Poly(Propylene)/Poly(Hydroxybutyrate) Blend and its Nanocomposite

Recycling of Bioplastics: Routes and Benefits

Biodegradation of Wasted Bioplastics in Natural and Industrial Environments: A Review

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