Iskanje po katalogu digitalne knjižnice

Opis: A digital twin of lyophilization units was developed to facilitate the scale-up of the lyophilization process from the laboratory to the commercial scale. Our focus was on ensuring successful technology transfer for manufacture of high-quality drug products. Traditionally, lyophilization models have been specific either to the equipment or to the vial. In this study, we integrated the equipment and the vial models in a way that they mutually influenced each other via boundary conditions (two-way coupling). We conducted two sets of calculations. Firstly, we performed steady-state simulations using Computational Fluid Dynamics (CFD) to simulate an ice slab test, which helped determine the equipment capability curve. Secondly, we carried out transient, coupled simulations using a coupled 3-D CFD and 1-D vial scale simulation model to mimic the primary drying phase in a lyophilizer. Using the coupled 3-D CFD and 1-D vial scale model, we were able to determine the product temperature, the sublimation rate and the cycle time based on the temporal and spatial conditions in the lyophilizer. The coupled approach was then applied to capture the effects of process disturbances and failure conditions in the lyophilizer, which enables a more robust process design.
Ključne besede: lyophilization, freeze-drying, sublimation
Objavljeno v DKUM: 13.03.2025; Ogledov: 0; Prenosov: 9
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Opis: Cellulose nanocrystals (CNCs) and chitosan (Cht) have been studied extensively for oxygen and water vapour barrier coatings in biodegradable, compostable or recyclable paper packaging. However, rare studies have been performed by using scalable, inexpensive, and fast continuous slot-die coating processes, and none yet in combination with fast' and high-throughput near-infrared (NIR) light energy drying. In this frame, we studied the feasibility of a moderately concentrated (11 wt%) anionic CNC and (2 wt%) cationic Cht coating (both containing 20 wt% sorbitol related to the weight of CNC/Cht), by using plain and pigment pre-treated papers. The effect of coating parameters (injection speed, dry thickness settings) were investigated on coating quantity (dry weight, thickness) and homogeneity (coverage), papers' structure (thickness, grammage, density), whiteness, surface wettability, barrier (air, oxygen and water vapour) properties and adhesion (surface strength). The coating homogeneity was dependent primarily on the suspensions' viscosity, and secondarily on the applied coating parameters, whereby CNCs could be applied at 1–2 times higher injection speeds (up to 80 mL/min) and versatile coating weights, but required a relatively longer time to dry. The CNCs thus exhibited outstanding air (4.2–1.5 nm/Pa s) and oxygen (2.7–1.1 cm3 mm/m2 d kPa) barrier performance at 50% RH and 22–33 g/m2 deposition, whereas on top deposited Cht (3–4 g/m2) reduced its wetting time and improved the water vapour barrier (0.23–0.28 g mm/m2 d Pa). The balanced barrier properties were achieved due to the polar characteristic of CNCs, the hydrophobic nature of Cht and the quantity of the applied bilayer coating that can provide sustainable paper-based packaging.
Ključne besede: paper, nanocellulose, chitosan, slot‑die coating, near-infrared (NIR) drying, barrier properties
Objavljeno v DKUM: 06.05.2024; Ogledov: 227; Prenosov: 18
Celotno besedilo (1,59 MB)
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Opis: The vial wall thermal conductivity and thickness effect on freeze-drying speed is simulated. A 2D axisymmetric numerical simulation of Mannitol freeze-drying is employed using the boundary element method. The originality of the presented approach lies in the simulation of heat transfer in the vial walls as an additional computational domain in contrast to the typical methodology without a vial wall. The numerical model was validated using our measurements and the measurements from the literature. Increasing the glass vial thickness from 1 mm to 2 mm has been found as the major factor in primary drying time, increasing the gravimetrical Kv up to 20 % for all the simulated chamber pressures. The effect of thermal conductivity was simulated using a polymer and aluminium vial replacing the standard glass vial of the same thickness. The polymer vial‘s decreased Kv value is 5.6 % at a low chamber pressure of 50 mTorr, and 12.2 % at 400 mTorr, which is in excellent agreement with the experiment. Using higher conductivity materials, for example, aluminium, only 3.7 % and 2.3 % Kv increase were computed for low and high chamber pressures respectively.
Ključne besede: freeze-drying, lyophilization speedup, vial heat conductivity, vial wall thickness, boundary element method
Objavljeno v DKUM: 16.04.2024; Ogledov: 264; Prenosov: 36
Celotno besedilo (1,88 MB)
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Opis: This review provides a concise overview of up-to-date developments in the processing of neat poly(lactic acid) (PLA), improvement in its properties, and preparation of advanced materials using a green medium (CO2 under elevated pressure). Pressurized CO2 in the dense and supercritical state is a superior alternative medium to organic solvents, as it is easily available, fully recyclable, has easily tunable properties, and can be completely removed from the final material without post-processing steps. This review summarizes the state of the art on PLA drying, impregnation, foaming, and particle generation by the employment of dense and supercritical CO2 for the development of new materials. An analysis of the effect of processing methods on the final material properties was focused on neat PLA and PLA with an addition of natural bioactive components. It was demonstrated that CO2-assisted processes enable the control of PLA properties, reduce operating times, and require less energy compared to conventional ones. The described environmentally friendly processing techniques and the versatility of PLA were employed for the preparation of foams, aerogels, scaffolds, microparticles, and nanoparticles, as well as bioactive materials. These PLA-based materials can find application in tissue engineering, drug delivery, active food packaging, compostable packaging, wastewater treatment, or thermal insulation, among others.
Ključne besede: aerogels, drying, foaming, impregnation, particle generation, PLA
Objavljeno v DKUM: 06.02.2024; Ogledov: 395; Prenosov: 31
Celotno besedilo (5,02 MB)
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Opis: Gold nanoparticles (AuNPs) have now been used in skin care creams for several years, with marketed anti-aging, moisturizing, and regenerative properties. Information on the harmful effects of these nanoparticles is lacking, a concern for the use of AuNPs as cosmetic ingredients. Testing AuNPs without the medium of a cosmetic product is a typical method for obtaining this information, which is mainly dependent on their size, shape, surface charge, and dose. As these properties depend on the surrounding medium, nanoparticles should be characterized in a skin cream without extraction from the cream’s complex medium as it may alter their physicochemical properties. The current study compares the sizes, morphology, and surface changes of produced dried AuNPs with a polyvinylpyrrolidone (PVP) stabilizer and AuNPs embedded in a cosmetic cream using a variety of characterization techniques (TEM, SEM, DLS, zeta potential, BET, UV–vis). The results show no observable differences in their shapes and sizes (spherical and irregular, average size of 28 nm) while their surface charges changed in the cream, indicating no major modification of their primary sizes, morphology, and the corresponding functional properties. They were present as individually dispersed nanoparticles and as groups or clusters of physically separated primary nanoparticles in both dry form and cream medium, showing suitable stability. Examination of AuNPs in a cosmetic cream is challenging due to the required conditions of various characterization techniques but necessary for obtaining a clear understanding of the AuNPs’ properties in cosmetic products as the surrounding medium is a critical factor for determining their beneficial or harmful effects in cosmetic products.
Ključne besede: gold nanoparticles, ultrasonic spray pyrolysis, freeze drying, characterization, creams
Objavljeno v DKUM: 19.04.2023; Ogledov: 769; Prenosov: 79
Celotno besedilo (5,34 MB)
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