1,720,980 research outputs found
Process-structure-property relationships in functionalized polyhydroxyalkanoate/ZnO nanocomposites for active packaging applications
No full textThe environmental challenges regarding conventional plastic packaging materials have drawn significant attention over the past years. In this regard, bioplastics have been proposed as more sustainable alternatives to conventional petroleum based plastics. Current drivers of the bioplastic market are the biobased and biodegradable polyhydroxyalkanoates (PHAs) which show potential for food packaging applications due to their wide range of functional properties. From the PHA family, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has shown great potential due to its flexibility and increased thermal stability. However, having medium oxygen barrier, relatively low strength, and no natural antibacterial properties, PHAs (including PHBHHx) need to be functionalized to broaden their application in packaging areas. The incorporation of nanoparticles (NPs) into the polymer matrix has shown potential to alter and enhance a wide range of properties. More specific, different studies have identified ZnO NPs as promising agents for improving the mechanical, thermal, antibacterial, UV and gas barrier properties of PHAs. ZnO NPs have been selected in this thesis for their relatively low cost in combination with their wide availability, relative safe nature and current use in a several applications. Despite the potential of ZnO NPs to enhance the properties of PHAs, there is no clear consensus in the literature regarding on how the processing, dispersion and NP characteristics exactly influence the functional properties of PHAs. Therefore, this thesis aimed to develop PHBHHx/ZnO nanocomposite films with good dispersion quality and added functional properties for food packaging applications. PHAs and their ZnO nanocomposites are processed using different techniques – including extrusion, injection molding, miniemulsion, ultrasonic spray coating (USSC), and centrifugal fiber spinning (CFS) – to distribute ZnO NPs in various locations within the material, such as in the bulk of the matrix or concentrated at the surface as coatings. In this way, this experimental work investigates on how the incorporation of ZnO NPs into PHBHHx influences the processing-structureproperty relationships, and specifically focusing on how the ZnO NP distribution, NP characteristics, and processing methods affect the combination of functional properties, such as crystallization, antibacterial activity, mechanical properties, and gas barrier performance. Firstly, this research demonstrates that the extrusion and injection molding parameters significantly affect the microstructure and mechanical properties of PHAs. By adjusting the melt-processing parameters such as mold and melt temperatures, it is possible to influence polymer chain orientation, crystallinity, and overall morphology (depending on the PHA type), which in turn can improve the mechanical properties like strength, flexibility, and rigidity. The selection of the appropriate PHA type in combination with achieving an equilibrium between the mechanical performance and efficient cycle times are essential for maximizing both functionality and productivity, which is highly relevant for industries looking to adopt PHAs as sustainable alternatives. One of the key findings of this research is that (i) the distribution of ZnO NPs within the PHBHHx/ZnO nanocomposites and (ii) the specific ZnO characteristics play a crucial role in the antibacterial and gas barrier properties compared to the ZnO NP concentration or dispersion quality. Coatings with higher surface concentrations of ZnO NPs, especially when applied using a combination of miniemulsion and USSC, outperform bulk melt-processed films regarding functional properties. USSC proves to be an effective method for depositing ZnO
NPs at the surface of PHBHHx films, allowing for improved nanoparticle dispersion. The use of miniemulsion particles can potentially minimize NP migration, as ZnO NPs remain encapsulated within the polymer matrix after processes like annealing and washing. The combination of USSC with an appropriate choice of the ZnO NP type shows great potential for active packaging applications, offering antibacterial, gas, and UV barrier properties while using lower ZnO concentrations compared to bulk melt-processing. USSC offers superior functional performance with roll-toroll capabilities, though it could present challenges in achieving uniform coatings over large areas. On the other hand, we showed that CFS allows fabrication of micro-to-nanofibers of PHBHHx and PHBHHx/ZnO, with the fiber morphology highly depending on the solution viscosity. The CFS fibers can be deposited as top layers after annealing. However, the CFS technique has limitations, particularly with respect to controlling the layer thickness and achieving a uniform coverage of the substrate. Despite these challenges, CFS shows potential for incorporating active ingredients such as NPs into nanofibers, making it promising for other applications beyond food packaging, such as in the biomedical field. In fact, we demonstrate the successful incorporation of hydrophilic compounds into hydrophobic PHBHHx nanofibers using a dual solvent system, highlighting the potential of CFS for drug delivery in wound healing applications. In conclusion, this thesis demonstrates that the method of incorporating ZnO NPs into PHBHHx, whether through melt processing, USSC, or CFS, has a profound
impact on the final functional properties. Melt processing remains advantageous for its industrial scalability, but USSC offers enhanced surface properties ideal for packaging applications, where antibacterial and gas barrier properties are critical. Although CFS is less suited for large-scale production at this stage, it holds significant promise for specialized applications such as drug delivery. Ultimately, this work provides valuable insights into the design and optimization of PHBHHx/ZnO nanocomposites, emphasizing the importance of processing techniques and ZnO NP distribution in achieving tailored properties for various
applications
Process-structure-property relationships in functionalized polyhydroxyalkanoate/ZnO nanocomposites for active packaging applications
No full textThe environmental challenges regarding conventional plastic packaging materials have drawn significant attention over the past years. In this regard, bioplastics have been proposed as more sustainable alternatives to conventional petroleum based plastics. Current drivers of the bioplastic market are the biobased and biodegradable polyhydroxyalkanoates (PHAs) which show potential for food packaging applications due to their wide range of functional properties. From the PHA family, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) has shown great potential due to its flexibility and increased thermal stability. However, having medium oxygen barrier, relatively low strength, and no natural antibacterial properties, PHAs (including PHBHHx) need to be functionalized to broaden their application in packaging areas. The incorporation of nanoparticles (NPs) into the polymer matrix has shown potential to alter and enhance a wide range of properties. More specific, different studies have identified ZnO NPs as promising agents for improving the mechanical, thermal, antibacterial, UV and gas barrier properties of PHAs. ZnO NPs have been selected in this thesis for their relatively low cost in combination with their wide availability, relative safe nature and current use in a several applications. Despite the potential of ZnO NPs to enhance the properties of PHAs, there is no clear consensus in the literature regarding on how the processing, dispersion and NP characteristics exactly influence the functional properties of PHAs. Therefore, this thesis aimed to develop PHBHHx/ZnO nanocomposite films with good dispersion quality and added functional properties for food packaging applications. PHAs and their ZnO nanocomposites are processed using different techniques – including extrusion, injection molding, miniemulsion, ultrasonic spray coating (USSC), and centrifugal fiber spinning (CFS) – to distribute ZnO NPs in various locations within the material, such as in the bulk of the matrix or concentrated at the surface as coatings. In this way, this experimental work investigates on how the incorporation of ZnO NPs into PHBHHx influences the processing-structureproperty relationships, and specifically focusing on how the ZnO NP distribution, NP characteristics, and processing methods affect the combination of functional properties, such as crystallization, antibacterial activity, mechanical properties, and gas barrier performance. Firstly, this research demonstrates that the extrusion and injection molding parameters significantly affect the microstructure and mechanical properties of PHAs. By adjusting the melt-processing parameters such as mold and melt temperatures, it is possible to influence polymer chain orientation, crystallinity, and overall morphology (depending on the PHA type), which in turn can improve the mechanical properties like strength, flexibility, and rigidity. The selection of the appropriate PHA type in combination with achieving an equilibrium between the mechanical performance and efficient cycle times are essential for maximizing both functionality and productivity, which is highly relevant for industries looking to adopt PHAs as sustainable alternatives. One of the key findings of this research is that (i) the distribution of ZnO NPs within the PHBHHx/ZnO nanocomposites and (ii) the specific ZnO characteristics play a crucial role in the antibacterial and gas barrier properties compared to the ZnO NP concentration or dispersion quality. Coatings with higher surface concentrations of ZnO NPs, especially when applied using a combination of miniemulsion and USSC, outperform bulk melt-processed films regarding functional properties. USSC proves to be an effective method for depositing ZnO
NPs at the surface of PHBHHx films, allowing for improved nanoparticle dispersion. The use of miniemulsion particles can potentially minimize NP migration, as ZnO NPs remain encapsulated within the polymer matrix after processes like annealing and washing. The combination of USSC with an appropriate choice of the ZnO NP type shows great potential for active packaging applications, offering antibacterial, gas, and UV barrier properties while using lower ZnO concentrations compared to bulk melt-processing. USSC offers superior functional performance with roll-toroll capabilities, though it could present challenges in achieving uniform coatings over large areas. On the other hand, we showed that CFS allows fabrication of micro-to-nanofibers of PHBHHx and PHBHHx/ZnO, with the fiber morphology highly depending on the solution viscosity. The CFS fibers can be deposited as top layers after annealing. However, the CFS technique has limitations, particularly with respect to controlling the layer thickness and achieving a uniform coverage of the substrate. Despite these challenges, CFS shows potential for incorporating active ingredients such as NPs into nanofibers, making it promising for other applications beyond food packaging, such as in the biomedical field. In fact, we demonstrate the successful incorporation of hydrophilic compounds into hydrophobic PHBHHx nanofibers using a dual solvent system, highlighting the potential of CFS for drug delivery in wound healing applications. In conclusion, this thesis demonstrates that the method of incorporating ZnO NPs into PHBHHx, whether through melt processing, USSC, or CFS, has a profound
impact on the final functional properties. Melt processing remains advantageous for its industrial scalability, but USSC offers enhanced surface properties ideal for packaging applications, where antibacterial and gas barrier properties are critical. Although CFS is less suited for large-scale production at this stage, it holds significant promise for specialized applications such as drug delivery. Ultimately, this work provides valuable insights into the design and optimization of PHBHHx/ZnO nanocomposites, emphasizing the importance of processing techniques and ZnO NP distribution in achieving tailored properties for various
applications
Characterization of ZnO/polyhydroxyalkanoate nanocomposites for packaging applications fabricated using melt-processing and centrifugal fiber spinning
No full textInnovative polyhydroxyalkanoate (PHA) biopolymers are among the main drivers of growth in the field of biobased and biodegradable plastics, with production capacities estimated to increase in the coming years. PHA polymer processing has been studied using different techniques, tough the relationship between specific processing parameters and mechanical performance remains to be further elucidated. Especially for the fabrication of nanocomposite films, different processing conditions can influence the dispersion of the nanoparticles in the polymer. We have produced zinc oxide (ZnO)/PHA nanocomposite films using a combination of dry mixing polymer powder and nanoparticles, twin-screw extrusion and compression molding. Alternatively, nanoparticles were incorporated during centrifugal fiber spinning and nanocomposite films were produced from these fibers. Finally, the functionality of the ZnO/PHA nanocomposite films was investigated for use as flexible packaging material based on mechanical, thermal, optical and barrier properties
Evaluation of melt-processed polyhydroxyalkanoates and zinc oxide nanocomposite films as flexible packaging materials
No full textEvaluation of melt-processed polyhydroxyalkanoates and zinc oxide nanocomposite films as flexible packaging materials
No full textUse of Miniemulsion for the Fabrication of Polyhydroxyalkanoate/ZnO Nanocomposite Films via Extrusion or Ultrasonic Spray Coating
No full textCentrifugal fiber spinning to fabricate polyhydroxyalkanoate/zinc oxide nanocomposite films: structure-property analysis
No full textCharacterization of ZnO/polyhydroxyalkanoate nanocomposites for packaging applications fabricated using melt-processing and centrifugal fiber spinning
No full textInnovative polyhydroxyalkanoate (PHA) biopolymers are among the main drivers of growth in the field of biobased and biodegradable plastics, with production capacities estimated to increase in the coming years. PHA polymer processing has been studied using different techniques, tough the relationship between specific processing parameters and mechanical performance remains to be further elucidated. Especially for the fabrication of nanocomposite films, different processing conditions can influence the dispersion of the nanoparticles in the polymer. We have produced zinc oxide (ZnO)/PHA nanocomposite films using a combination of dry mixing polymer powder and nanoparticles, twin-screw extrusion and compression molding. Alternatively, nanoparticles were incorporated during centrifugal fiber spinning and nanocomposite films were produced from these fibers. Finally, the functionality of the ZnO/PHA nanocomposite films was investigated for use as flexible packaging material based on mechanical, thermal, optical and barrier properties
Centrifugal fiber spinning to fabricate polyhydroxyalkanoate/zinc oxide nanocomposite films: structure-property analysis
No full textProcessing and Properties of Polyhydroxyalkanoate/ZnO Nanocomposites: A Review of Their Potential as Sustainable Packaging Materials
Full text linkThe escalating environmental concerns associated with conventional plastic packaging have accelerated the development of sustainable alternatives, making food packaging a focus area for innovation. Bioplastics, particularly polyhydroxyalkanoates (PHAs), have emerged as potential candidates due to their biobased origin, biodegradability, and biocompatibility. PHAs stand out for their good mechanical and medium gas permeability properties, making them promising materials for food packaging applications. In parallel, zinc oxide (ZnO) nanoparticles (NPs) have gained attention for their antimicrobial properties and ability to enhance the mechanical and barrier properties of (bio)polymers. This review aims to provide a comprehensive introduction to the research on PHA/ZnO nanocomposites. It starts with the importance and current challenges of food packaging, followed by a discussion on the opportunities of bioplastics and PHAs. Next, the synthesis, properties, and application areas of ZnO NPs are discussed to introduce their potential use in (bio)plastic food packaging. Early research on PHA/ZnO nanocomposites has focused on solvent-assisted production methods, whereas novel technologies can offer additional possibilities with regard to industrial upscaling, safer or cheaper processing, or more specific incorporation of ZnO NPs in the matrix or on the surface of PHA films or fibers. Here, the use of solvent casting, melt processing, electrospinning, centrifugal fiber spinning, miniemulsion encapsulation, and ultrasonic spray coating to produce PHA/ZnO nanocomposites is explained. Finally, an overview is given of the reported effects of ZnO NP incorporation on thermal, mechanical, gas barrier, UV barrier, and antimicrobial properties in ZnO nanocomposites based on poly(3-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate). We conclude that the functionality of PHA materials can be improved by optimizing the ZnO incorporation process and the complex interplay between intrinsic ZnO NP properties, dispersion quality, matrix-filler interactions, and crystallinity. Further research regarding the antimicrobial efficiency and potential migration of ZnO NPs in food (simulants) and the End-of-Life will determine the market potential of PHA/ZnO nanocomposites as active packaging material.Funding:
This research was funded by the Special Research Fund (BOF) of Hasselt University, grant number BOF20DOC06.
Acknowledgments:
The authors acknowledge all co-workers of MPR&S, imo-imomec, UHasselt, and beyond, for fruitful discussions on PHA research throughout the years
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