Iskanje po katalogu digitalne knjižnice

Opis: Bio-based poly(lactic acid) (PLA) composite films were produced using unmodified soda micro- or nano-lignin as a green filler at four different contents, between 0.5 wt% and 5 wt%. The PLA– lignin composite polymers were synthesized by solvent casting to prepare a masterbatch, followed by melt mixing. The composites were then converted into films, to evaluate the effect of lignin content and size on their physicochemical and mechanical properties. Differential scanning calorimetry (DSC), supported by polarized light microscopy (PLM), infrared spectroscopy (FTIR-ATR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to investigate the PLA crystallization and the interactions with Lignin (L) and Nanolignin (NL). The presence of both fillers (L and NL) had a negligible effect on the glass transition temperature (chain diffusion). However, it resulted in suppression of the corresponding change in heat capacity. This was indicative of a partial immobilization of the PLA chains on the lignin entities, due to interfacial interactions, which was slightly stronger in the case of NL. Lignin was also found to facilitate crystallization, in terms of nucleation; whereas, this was not clear in the crystalline fraction. The addition of L and NL led to systematically larger crystallites compared with neat PLA, which, combined with the higher melting temperature, provided indications of a denser crystal structure in the composites. The mechanical, optical, antioxidant, and surface properties of the composite films were also investigated. The tensile strength and Young’s modulus were improved by the addition of L and especially NL. The UV-blocking and antioxidant properties of the composite films were also enhanced, especially at higher filler contents. Importantly, the PLA–NL composite films constantly outperformed their PLA–L counterparts, due to the finer dispersion of NL in the PLA matrix, as verified by the TEM micrographs. These results suggest that bio-based and biodegradable PLA films filled with L, and particularly NL, can be employed as competitive and green alternatives in the food packaging industry.
Ključne besede: poly(lactic acid), PLA, lignin, nanolignin, composite films, nucleation, mechanical properties, antioxidant activity, food packaging
Objavljeno v DKUM: 26.03.2025; Ogledov: 0; Prenosov: 1
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Opis: This study presents the synthesis and characterization of a series of multiblock copolymers, poly(ethylene 2,5-furandicarboxylate)-poly(ε-caprolactone) (PEF-PCL), created through a combination of the two-step melt polycondensation method and ring opening polymerization, as sustainable alternatives to fossil-based plastics. The structural confirmation of these block copolymers was achieved through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), ensuring the successful integration of PEF and PCL segments. X-ray Photoelectron Spectroscopy (XPS) was employed for chemical bonding and quantitative analysis, providing insights into the distribution and compatibility of the copolymer components. Differential Scanning Calorimetry (DSC) analysis revealed a single glass transition temperature (Tg), indicating the effective plasticizing effect of PCL on PEF, which enhances the flexibility of the copolymers. X-ray Diffraction (XRD) studies highlight the complex relationship between PCL content and crystallization in PEF-PCL block copolymers, emphasizing the need to balance crystallinity and mechanical properties for optimal material performance. Broadband Dielectric Spectroscopy (BDS) confirmed excellent distribution of PEF-PCL without phase separation, which is vital for maintaining consistent material properties. Mechanical properties were evaluated using Nanoindentation testing, demonstrating the potential of these copolymers as flexible packaging materials due to their enhanced mechanical strength and flexibility. The study concludes that PEF-PCL block copolymers are promising candidates for sustainable packaging solutions, combining environmental benefits with desirable material properties.
Ključne besede: poly(ethylene furanoate), poly(ε-caprolactone), block copolymers, thermal properties, molecular dynamics, crystallinity, mechanical properties, flexible packaging
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 5
Celotno besedilo (4,73 MB)
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Opis: Following the banning of expanded polystyrene packaging material, the fast food restaurant industry was serendipitously plunged into green sourcing initiatives for its packaging materials leading to heightened efforts on evaluating the suitability of various suppliers of green packaging material. This study therefore sought to assess the performance of selected suppliers on supplier performance metrics of total cost of ownership, quality of sourced material and delivery performance, in Zimbabwe’s restaurant industry. Methodology: Data was collected from senior procurement officers of 30 officially registered fast food restaurants in Zimbabwe. Each restaurant randomly selected 5 suppliers from their supplier lists. Each unit was asked to rate their 5 major suppliers of packaging material leading to an effective sample size of 150 suppliers. Structural Equation Modeling (SEM) was used to analyse data in AMOS. The five steps in SEM, that is: model specification, model identification, parameter estimation, model evaluation and modification were done. Findings: The findings in this study revealed that green sourcing leads to improved procurement performance in terms of total cost of ownership, quality of the materials sourced, and delivery performance. Implications for theory and practice: It was therefore recommended that practically the restaurant industry should explore various options of green packaging material ranging from recyclable and reusable plastic, paper, aluminium and steel material. Originality and value: Although the study was done in a single market, there is dearth in literature on green sourcing in frontier markets, of which the study provides empirical evidence from the restaurant industry in SubSaharan Africa.
Ključne besede: green sourcing, supplier evaluation, fast food restaurant, frontier markets, supplier performance metrics, green packaging material, total cost of ownership, quality of sourced material, delivery performance
Objavljeno v DKUM: 23.08.2024; Ogledov: 80; Prenosov: 7
Celotno besedilo (1,33 MB)
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Opis: UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.
Ključne besede: chitosan, plant extracts, polypropylene, active packaging, surface characterization, bioactivity
Objavljeno v DKUM: 27.05.2024; Ogledov: 241; Prenosov: 22
Celotno besedilo (4,75 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: 28
Celotno besedilo (5,51 MB)
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