Iskanje po katalogu digitalne knjižnice

Opis: This study addresses the inherent shortcomings of poly (lactic acid) (PLA), a biodegradable polymer widely used in industries such as packaging and biomedical applications. The principal challenge of PLA resides in its low crystallinity, which detrimentally affects its mechanical properties and thermal stability. Additionally, PLA is prone to water and hydrolysis, which compromises its chemical resistance and can lead to degradation over time. To overcome surmount these limitations, the study focuses on the development of hybrid films through the blending of PLA with poly (l-lactide-co-ethylene adipate) (pLEA) block copolymers. The objective is to augment the crystallinity, mechanical performance, and chemical resistance of the resulting materials. The study employs a range of analytical techniques, including Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Polarised Light Microscopy (PLM), Differential Scanning Calorimetry (DSC), and Thermogravimetric Analysis (TGA), to thoroughly characterize the copolymers and blend films. By systematically selecting blending ratios and processing methodologies, the study demonstrates enhancements in the properties of the resultant hybrid films compared to neat PLA. Specifically, the structure of films significantly changed from amorphous to crystalline in a short duration - 5 min, of annealing., leading to better tensile strength, modulus and reduced wettability, which are crucial for applications requiring durability and resistance to environmental factors. Films made from 30 wt% of pLEA 97.5/2.5 with 70 % of PLA by fast cooling exhibited outstanding mechanical properties, with a tensile strength 20 MPa higher than that of neat PLA films. Additionally, the chemical resistance may be improved, as evidenced by a decrease in wettability by approximately 15° and a reduction in the polar component of the surface free energy by about 7 mN/m. Hydrophobic, water-repellent materials resist penetration by water and other polar solvents, reducing exposure to corrosive substances and enhancing chemical resistance through barrier protection. Overall, this research addresses the limitations of PLA through innovative copolymerization and blending strategies, offering valuable insights into optimizing the material's properties for various practical applications.
Ključne besede: Poly(lactic acid), Poly(l-lactide-co-ethylene adipate), copolymer, blend, crystallinity
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 7
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Opis: Poly(ethylene 2,5-furan dicarboxylate) (PEF) based nanocomposites containing different nanoparticles like Ag, TiO2, ZnO, ZrO2 Ce-Bioglass, have been synthesized via in-situ polymerization techniques targeting food pack aging applications. Zeta potential measurements showed an increase in the negative zeta potential value due to an increase in the surface charge density of the nanocomposites. Thermogravimetric analysis results proved that, except PEF-ZnO nanocomposite, all the other nanocomposites exhibited good resistance to thermal degradation without serious mass loss until 330 ◦C. Thermal decomposition kinetic analysis and the dependence of activation energy on the degree of conversion (α), indicated that the presence of ZnO nanoparticles influences, the degradation mechanism of PEF. In contrast, the presence of Ce-Bioglass nanoparticles leads to a slower degra dation process, contributing to the enhanced resistance to thermal degradation of the PEF-Bioglass nano composite. The thermal degradation mechanism of PEF nanocomposites analyzed by pyrolysis‒gas chromatography/mass spectrometry (Py-GC/MS) indicated that the primary thermal degradation mechanism for the studied nanocomposites was β-hydrogen bond scission, while to a lesser extent, α-hydrogen bond scission products were noted in PEF-TiO2 and PEF-ZrO2 nanocomposites.
Ključne besede: bio based polymers, Poly(ethylene 2, 5-furan dicarboxylate), nanoparticles, thermal properties, nanocomposites, decomposition mechanism
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 4
Celotno besedilo (1,89 MB)
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Opis: Furanoate polyesters are an extremely promising new class of materials for packaging applications, particularly furanoate-based nanocomposites, which have gained a high interest level in research and development in both academia and industries. The monomers utilised for the synthesis of furanoate-based polyesters were derived from lignocellulosic biomass, which is essential for both eco-friendliness and sustainability. Also, these polyesters have a lower carbon footprint compared to fossil-based plastics, contributing to greenhouse gas reduction. The furanoate-based nanocomposites exhibit enhanced performance characteristics, such as high thermal stability, excellent mechanical strength, superior barrier resistance, and good bacteriostatic rate, making them suitable for a wide range of industrial applications, especially for food-packaging applications. This paper reviews the recent trends in the synthesis routes of monomers, such as the various catalytic activities involved in the oxidation of 5(hydroxymethyl)furfural (HMF) into 2,5-furandicarboxylic acid (FDCA) and its ester, dimethyl furan-2,5-dicarboxylate (DMFD). In addition, this review explores the fabrication of different furanoate-based nanocomposites prepared by in situ polymerization, by melt mixing or solvent evaporation methods, and by using different types of nanoparticles to enhance the overall material properties of the resulting nanocomposites. Emphasis was given to presenting the effect of these nanoparticles on the furanoate polyester’s properties.
Ključne besede: 2, 5-furandicarboxylic acid, dimethyl furan-2, 5-dicarboxylat, furanoate polyesters, furanoate nanocomposites, thermal properties, mechanical properties, antibacterial properties, sustainable packaging
Objavljeno v DKUM: 10.03.2025; Ogledov: 0; Prenosov: 5
Celotno besedilo (4,54 MB)
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Ključne besede: food packaging, active agents, bulk preparation techniques, antibacterial and antioxidant properties
Objavljeno v DKUM: 11.04.2024; Ogledov: 251; Prenosov: 26
Celotno besedilo (5,51 MB)
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Opis: Poly(ethylene furanoate) (PEF)-based nanocomposites were fabricated with silver (Ag) and titanium dioxide (TiO2) nanoparticles by the in-situ polymerization method. The importance of this research work is to extend the usage of PEF-based nanocomposites with improved material properties. The PEF-Ag and PEF-TiO2 nanocomposites showed a significant improvement in color concentration, as determined by the color colorimeter. Scanning electron microscopy (SEM) photographs revealed the appearance of small aggregates on the surface of nanocomposites. According to crystallinity investigations, neat PEF and nanocomposites exhibit crystalline fraction between 0–6%, whereas annealed samples showed a degree of crystallinity value above 25%. Combining the structural and molecular dynamics observations from broadband dielectric spectroscopy (BDS) measurements found strong interactions between polymer chains and nanoparticles. Contact angle results exhibited a decrease in the wetting angle of nanocomposites compared to neat PEF. Finally, antimicrobial studies have been conducted, reporting a significant rise in inhibition of over 15% for both nanocomposite films against gram-positive and gram-negative bacteria. From the overall results, the synthesized PEF-based nanocomposites with enhanced thermal and antimicrobial properties may be optimized and utilized for the secondary packaging (unintended food-contact) materials.
Ključne besede: active agents, antimicrobial studies, biobased polymers, crystallinity, poly(ethylene 2, 5-furandicarboxylate)
Objavljeno v DKUM: 03.04.2024; Ogledov: 214; Prenosov: 12
Celotno besedilo (3,13 MB)
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