Iskanje po katalogu digitalne knjižnice

Opis: The objective of the master thesis is to determine the filling properties of injection moulding process for newly created material, and to understand how the variation of processing parameters affects the flow possibilities. In thesis two materials were analysed, i.e. neat PLA material, which was used as a benchmark material and newly created composite CitrusPLA that is based on biodegradable PLA matrix and reinforced with citrus fibres. To fulfil the aim, the virtual and experimental design of experiment with the Taguchi methodology was conducted with use of spiral flow test, where the flow length of material through mould cavity was observed. The experimental results were the basis for the accuracy validation of numerical results and also to determine the optimum process parameters for injection moulding products with best flow conditions through statistical evaluation. It has been concluded that the newly created composite has lower viscosity compared to benchmark virgin PLA which results in better flow conditions in spiral flow test analysis. Both materials have the same optimal conditions in terms of flow conditions. The contribution of mould temperature is in both cases negligible. However, other two variated parameters i.e. melt temperature and injection speed have higher influence on filling characteristics for both materials.
Ključne besede: injection moulding optimization, material characterization, Moldflow, injection moulding simulations, Taguchi DOE, bio-composites, citrus waste fibres, PLA
Objavljeno v DKUM: 07.06.2019; Ogledov: 1665; Prenosov: 40
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Opis: The aim of this research was to apply three different types of zeolites and the combination thereof in the form of a very fine powder, together with different chemicals and additives on polyamide knitted fabric according to an industrially acceptable exhaustion procedure in order to study changes in the morphology, optical properties and wettability of surfaces. Zeolites were analysed using Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and gas physiosorption. Additionally, the morphology of zeolite-coated surfaces was examined closely using SEM, while changes in molecular-chemical level were examined by means of IR spectroscopy. Optical properties were studied using CIE colour measurement and diff use reflectance profi le determination, while the hydrophilic/hydrophobic character was examined using goniometry. The obtained results show the suitability of the employed exhaustion procedure, depending on the type of zeolite and the composition of the treatment bath. The results also provided evidence of the enhanced wettability of PA fabrics using 4A and 13X zeolites in combination with selected additives.
Ključne besede: zeolites, polyamide fibres, exhaustion, surface modification, wettability
Objavljeno v DKUM: 31.08.2017; Ogledov: 2368; Prenosov: 442
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Opis: Wettability and sorptivity improvements for different textile materials are the major tasks during textile finishing. In order to improve the sorption characteristics of a cellulose fabric, different pre-treatment processes are applied, usually washing, bleaching and mecerisation. Differences in the sorption properties of untreated and pretreated (washed and bleached) regenerated cellulose fibres were obtained using tensiometry and compared with the classical method for determining moisture adsorption. Results show that compared to raw fibres, viscose fibres have the highest moisture and the smallest contact angle whilst modal fibres have the biggest contact angle. Pretreatment increases the sorption abilities and makes the material more accessible to chemicals used in the finishing process. Using the conventional method, it can be confirmed that fibres with the highest moisture have the smallest contact angle (tensiometry).
Ključne besede: textile materials, regenerated cellulose fibres, sorption, pretreatment, tensiometry
Objavljeno v DKUM: 05.07.2017; Ogledov: 1223; Prenosov: 136
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Opis: The aim of this dissertation was to develop a novel medical tampon for alternative gynaecological treatment using chitosan nanoparticles as an antimicrobial agent or as a drug delivery system. For this purpose viscose tampon band was used and functionalized with chitosan and trimethyl chitosan nanoparticles. A comprehensive of interactions between chitosan and cellulose as well as characterization of prepared materials were done. At the beginning, chitosan (CS) and trimethyl chitosan (TMC) solutions, as well as nanoparticles synthesised by ionic gelation were studied. Their characterization was focused on determining the charge and antimicrobial properties against common pathogenic microorganism. The influence of cationic charge on the inhibition of microbial growth was confirmed. Since CS and TMC solutions and nanoparticles dispersions exhibited antibacterial activity against Lactobacillus, a detailed investigation in chitosan’s antimicrobial mode of action was performed using a novel diffusion nuclear magnetic resonance (D-NMR). D-NMR allowed the monitoring of intra- and extracellular water exchange from the cells indicating the membrane alteration and leakage of intracellular constituencies. Further, in order to study the adsorption phenomena and molecular interactions between CS/TMC (solution or nanoparticles) and cellulose material, model cellulose surfaces were used, and adsorption was studied by quartz crystal microbalance with dissipation. CS and TMC were favourably deposited onto cellulose model surface at higher ionic strength, higher pH values, i.e. factors causing lower solubility, where the presence of electrostatic interactions was negligible and non-electrostatic interactions were dominant. The knowledge gained from the model surfaces was extremely helpful in characterization of real systems, i.e. functionalized cellulose fibres and for understanding the obtained results. Immobilization of CS and TMC (in the form of solution and/or nanoparticles) onto cellulose viscose fibres was confirmed with several analytical methods. The attachment of chitosan onto fibres was reversible, as endorsed with desorption studies mimicking the conditions of vaginal usage. Evaluation of antimicrobial properties was performed using two different techniques, both revealing a high inhibition of the tested microorganism. In addition, Lactobacillus susceptibility testing has shown that chitosan-coated fibres do not have any negative influence on the resident microbiota. Assessment of in-vitro cytotoxicity demonstrated that samples do not cause a cytotoxic effect in direct contact. Additionally, model drug was incorporated into chitosan nanoparticles and subsequently attached onto fibres in order to create modern, vaginal drug delivery systems. Antimicrobial medical textiles investigated in the scope of this dissertation show the potential for their exploitation in gynaecological field as preventive or curative treatment without triggering any adverse effects for the user.
Ključne besede: chitosan, N, N, N-trimethyl chitosan, nanoparticles, antimicrobial activity, cellulose model films, regenerated cellulose fibres, diffusion nuclear magnetic resonance, quartz crystal microbalance, vaginal infections, drug delivery systems, cytotoxicity
Objavljeno v DKUM: 13.02.2014; Ogledov: 3877; Prenosov: 204
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Opis: The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.
Ključne besede: textiles, PA 6 fibres, dyeing, dyeability, fibre structure, crystallinity, chemical modification
Objavljeno v DKUM: 01.06.2012; Ogledov: 2331; Prenosov: 36
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