Academic literature on the topic 'Chemická předúprava'

CZ: Přítomnost reziduí plastů v životním prostředí je v poslední době diskutována napříč společností kvůli zamořování oceánů a nedostatečné recyklaci plastových výrobků. Okem nepostřehnutelné mikroplasty, které se do vody dostávají užíváním produktů osobní péče a rozkladem syntetických polymerů nejsou v současnosti dostatečně odstraňovány při úpravě vody a mohou se dostávat do trávicího traktu konzumentů. Zdravotní rizika pro člověka nejsou doposud známá, přesto lze předpokládat, že bude výskyt mikroplastů ve vodách monitorován. Naším cílem bylo vypracování finančně dostupné a dostatečně přesné metody pro následnou analýzu mikroplastů ve vodách, jež by mohla být rutinně prováděna v kontrolních laboratořích. Vzorky vláken byly podrobeny předúpravě sloužící k izolaci syntetických mikrovláken od ostatních materiálů, které mohou způsobit zkreslení kvantitativní analýzy mikroplastů. Byla sledována reakce dvou testovaných materiálů na jejich expozici různým teplotním a oxidačním podmínkám s využitím peroxidu vodíku jako oxidačního činidla a změna barvy vláken. Jako optimální se jeví osmihodinová expozice vzorku v 30% roztoku peroxidu vodíku při teplotě 60 °C s následnou analýzou mikroplastů infračervenou spektroskopií (ATR-IR). Naše výsledky by mohly být využity při vytváření komplexní metodiky kvalitativního a kvantitativního hodnocení mikroplastů. EN: Occurrence of plastics in the natural environment is one of the hot topics in the area of environmental studies due to the ocean contamination and insufficient amount of plastics' recycling. Microplastics which cannot be seen by the naked eye are not effectively removed from the water during drinking water treatment and afterwards they enter the human body through the digestive tract. Even though there is no evidence of harmful effects on health, it is assumed that the presence of microplastics in water will be monitored. Our work was aimed on the development of a methodology for the pretreatment of synthetic microfibers based microplastics followed by their subsequent infrared analysis, which can be routine performed in laboratories. Microfibers were subjected to various thermal and oxidative conditions, where hydrogen peroxide was used as an oxidizing agent. Effects of the exposure on changes in chemical structure and colour of fibres were analysed. Optimal exposure conditions for plastic microfibers' pretreatment concerns the exposure in 30% solution of hydrogen peroxide at 60 °C for 8 hours followed by infrared spectroscopy (ATR-IR). We believe that our results can be utilized for the creating complex methodology of qualitative and quantitative microplastics' evaluation.

This diploma thesis is focused on study of chemical and enzymatical hydrolysis of raw wood material. The aim of this work was to find the suitable method for pretreatment of selected lignocellulose materials. The theoretical part deals with characterization of lignocellulosic material and its components. There are also subscribed various pretreatment methods and their effect on hydrolysis of sawdust. In experimental part of the work the most appropriate approach of pretreatment and hydrolysis of sawdust was studied. Criteria for the selection of suitable method was concentration of saccharides as desired product of hydrolysis and also concentration of the most important microbial inhibitors - polyphenols. Application of 96% ethanol or 5% H2O2 were identified as the most promising pretreatment methods which enhanced yields of fermentable sugars about 30 %. Further, we also performed cultivation of bacteria Burkholderia cepacia and bacteria Burkholderia sacchari using solution obtained by hydrolysis of lignocellulose material.

This diploma thesis deals with various procedures of surface pretreatment of steel and aluminum alloy for subsequent application of powder coating substance. The work begins with an overview of the general characteristics of the materials used. The core part of the work is then a summary of the individual methods of pretreatment that can be used to modify the material surface. A special chapter is devoted to methodologies for the application of powder substances. Before separate application, the sample must first be carefully pretreated to ensure removal of organic compounds (e.g. oils from primary processing - grinding, cutting), or dust impurities to ensure the correct barrier effect. After dividing the individual methods of surface preparation, a powder paint system with a total thickness of approximately 50 µm is applied to the test material. Samples with different surface pretreatments will be compared both in terms of mechanical properties and in terms of electrochemical properties.

Theoretical part PhD thesis describes bending of sheets especially with a small bend radius and the distribution of deformation and describes the parameters of bent sheet. As the test sheets were treated by cataphoretic coating is this method described together with pretreatment of sheet. The practical part is focused on the principle multi-jet plasma system and treatment of the steel surface and examines the bent surfaces of the steel sheets with different variants of applying the coating. Selected samples are bent on the multifunction graduated bending jig and subjected to the Erichsen test and deduced results using plasma system and without the use of plasma system. In the experimental part were examined samples treated by multi-jet plasma system and subsequently bent on the multifunction graduated bending jig. Compares the results of individual experiments in system steel – base coat – plasma – topcoat. And also compares mutual combinations of various kinds of modifying the surfaces of steel samples with different coatings. Selected samples were tested for tensile test and the results were processed from this test. For selected samples was calculated hardening exponent. Another experiment consists in applying a circle at equal samples and subsequently the samples were bent under a defined radius and were determined tensile and compressive deformation. Samples of sheets were then embedded in the resin and then examined under a microscope, where they were divided into several categories and was determined optimal composition multi-jet plasma system for selected samples and the specific coatings on sheet plate with a maximum adhesion of the coating to the steel base. Selected measured values were subjected statistical control.

This thesis resumes both theoretical and practical knowledge with surface protection by wet painting which the student achieved during her studies and within her practice which she got in the painting shop of cabs for building, handling and agricultural machines. In her thesis the student has found out that one of current trends focuses on the method which is ecologically friendly and preserves paint lifetime. To achieve that, ED-coat painting is used first and then followed by the painting of waterborne paint. Within the scope of her thesis objective she has also optimised the process of surface protection respective technological pre-treatments and parameters which are carried out during ED-coat and e-coat painting, such as optimal thickness of coating, temperatures or technological time outs.

The content of this master’s thesis are methods of pretreatment and coating of the surface of PET to produce conductive copper structure and quality control. Thesis also includes theoretical analysis of these methods. Physical and chemical techniques of surface pretreatment methods are discussed in the theoretical part as well as methods making surface of substrate conductive, the subsequent galvanic copper plating and quality control of coating and testing of the adhesion between layers. The experimental part focuses on two methods of the polymer material surface pretreatments. The properties of these pretreatments were evaluated by using the atomic force microscopy and detection of surface energy by wetting and contact angle measurements. The surface is making conductive with cathode sputtering and electrochemical coating of copper. Adhesion of layers is tested mainly with scratch test and other methods. The results of these sub-operations are used for the realization of multi-layer conductive structures.