Self-organized biopolymer layers and coatings with mineral fillers for special applications.

Yousef MURTAJA

Doctoral thesis

Abstract:

This dissertation emphasizes the application of mineral fillers in natural biopolymer layers for specific purposes, polymer composites, and nanofillers and their properties. The thesis is presented as a collection of scientific research in the form of thematically arranged published papers, supported by an annotated theoretical framework. Alternatives to artificial coatings are available in natural biopolymers with added mineral fillers, which are environmentally friendly and sustainable in the long term. Integrating mineral fillers into these coatings can improve their properties to meet specific application requirements. Nanofillers added to polymer composites can improve mechanical strength and resistance to high temperatures without any degradation effect. The first research paper confirms that perlite plays a key role in the thermal and mechanical properties of HDPE-based nanocomposite materials. Young's tensile modulus increases with increasing filler material concentration, leading to an increase in stiffness. The degree of fracture toughness decreases with increasing concentration of perlite at brittle fracture. However, higher concentrations of filler material are also associated with the measured ductile fracture behavior. SEM analysis confirms the strong bonding between the polymer matrix chains and the filler particle.Further research revealed the effect of two different types of inorganic mineral fillers, calcium carbonate nanoparticles, and mineral nano silicates (nano clay), on the mechanical behavior of HDPE nanocomposite polymers in a semi-operational test. The study focuses on the characterization of fillers uniformly dispersed in the samples using SEM imaging techniques, X-ray analysis of dispersion spectra, and the TEM method. However, the addition of these fillers improves the technical properties of the polymer composites as shown by the combination of the elastic modulus and the microhardness observed. The amount and extent of fillers in the composites determine their elastic mechanical behavior and plasticity.The technical properties of epoxy/HNTs & GnPs composites are the focus of the third research study. These shows that planar particles exhibit mutual sliding during mechanical testing, thereby reducing the overall stiffness of GnPs nanocomposites and increasing their ductility and plasticity. The stiffness of epoxy/HNT composites decreases with the addition of nanofiller, as indicated by the observed lower Young's modulus in tension. The study reveals the different mechanical responses of the tested materials due to the ductile and brittle fracture processes occurring. In addition, the resistance of polyurethane foams to thermal degradation, including thermal stress-induced changes in their mechanical properties, is studied using selected physicochemical methods. The effect of increased relative humidity on degradation, leading to a decrease in stiffness and permanent deformation, was also found. In addition, the dynamic-mechanical properties of the studied composite materials were investigated by measuring the vibration damping excited by a single degree of freedom oscillatory system (SDOF). In this way, the changes in elasticity caused by different conditioning of the studied samples, which led to progressive degradation and loss of thermal stability, were monitored. In summary, this dissertation provides valuable insights into the latest research trends and developments in natural biopolymer films with mineral fillers, their properties, and potential applications. The results of the studies in this dissertation provide important data for the design of sustainable and environmentally friendly materials for specific needs and offer possible directions for scientific developments in the field of polymer composites and nanofillers.

Abstract:

This dissertation emphasizes the application of mineral fillers in natural biopolymer layers for specific purposes, polymer composites, and nanofillers and their properties. The thesis is presented as a collection of scientific research in the form of thematically arranged published papers, supported by an annotated theoretical framework. Alternatives to artificial coatings are available in natural biopolymers with added mineral fillers, which are environmentally friendly and sustainable in the long term. Integrating mineral fillers into these coatings can improve their properties to meet specific application requirements. Nanofillers added to polymer composites can improve mechanical strength and resistance to high temperatures without any degradation effect. The first research paper confirms that perlite plays a key role in the thermal and mechanical properties of HDPE-based nanocomposite materials. Young's tensile modulus increases with increasing filler material concentration, leading to an increase in stiffness. The degree of fracture toughness decreases with increasing concentration of perlite at brittle fracture. However, higher concentrations of filler material are also associated with the measured ductile fracture behavior. SEM analysis confirms the strong bonding between the polymer matrix chains and the filler particle.Further research revealed the effect of two different types of inorganic mineral fillers, calcium carbonate nanoparticles, and mineral nano silicates (nano clay), on the mechanical behavior of HDPE nanocomposite polymers in a semi-operational test. The study focuses on the characterization of fillers uniformly dispersed in the samples using SEM imaging techniques, X-ray analysis of dispersion spectra, and the TEM method. However, the addition of these fillers improves the technical properties of the polymer composites as shown by the combination of the elastic modulus and the microhardness observed. The amount and extent of fillers in the composites determine their elastic mechanical behavior and plasticity.The technical properties of epoxy/HNTs & GnPs composites are the focus of the third research study. These shows that planar particles exhibit mutual sliding during mechanical testing, thereby reducing the overall stiffness of GnPs nanocomposites and increasing their ductility and plasticity. The stiffness of epoxy/HNT composites decreases with the addition of nanofiller, as indicated by the observed lower Young's modulus in tension. The study reveals the different mechanical responses of the tested materials due to the ductile and brittle fracture processes occurring. In addition, the resistance of polyurethane foams to thermal degradation, including thermal stress-induced changes in their mechanical properties, is studied using selected physicochemical methods. The effect of increased relative humidity on degradation, leading to a decrease in stiffness and permanent deformation, was also found. In addition, the dynamic-mechanical properties of the studied composite materials were investigated by measuring the vibration damping excited by a single degree of freedom oscillatory system (SDOF). In this way, the changes in elasticity caused by different conditioning of the studied samples, which led to progressive degradation and loss of thermal stability, were monitored. In summary, this dissertation provides valuable insights into the latest research trends and developments in natural biopolymer films with mineral fillers, their properties, and potential applications. The results of the studies in this dissertation provide important data for the design of sustainable and environmentally friendly materials for specific needs and offer possible directions for scientific developments in the field of polymer composites and nanofillers.

Keywords

Biopolymer, Nanocomposite, Nanofilers, Coating, Mineral Perlite, HDPE Nanocomposite, Young's Modulus, Uniaxial Tensile Test, Fracture, Ductile, Stiffness, SEM, TEM, Brittle, Nano Calcium Carbonate, Nano Clay, Elastic Behaviour, Plasticity, Fracture Toughness, Stress/Stain Curve, Microhardness, Polyurethane Foams, Damping, Degradation, Single Degree of Freedom, Mechanical Strength, Physicochemical, Diffusion of Polymers, Surface Tension, Swelling, Dissolution, Swollen Surface Layer, Kinetics of Swelling, Kinetics of Dissolution, Crosslinking, Thermal Analysis, Charpy Impact Testing, Displacement Transmissibility Measurement, Dynamic Mechanical Vibration, Sound Absorption, Deformation Rates, Elongation, Maximum Force, Frequency Peak, Matrix, Destructive, Excitation, Melting Point, Surface Free Energy, Indentation Modulus, Upper Yield, Crystallinity, Strain at Break, Interface, Epoxy/Graphene Nanocomposite, Epoxy/Halloysite Nanocomposites, Uniaxial 3-Point Bending Test, Nanotubes, Linear, Inertial Mass, Resonance Frequency, Relative Humidity, Hydrolysis, Conditioning Time, Weathering, Conditioning Temperature, Differential Thermal Analysis, Thermogravimetric Analysis.

Language used: English

Date on which the thesis was submitted / produced: 31. 8. 2023

Thesis defence

• Supervisor: prof. Ing. Lubomír Lapčík, CSc.

Palacký University Olomouc

Faculty of Science

Doctoral programme / field:
Nanomaterial Chemistry / Nanomaterial Chemistry