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Development of a new ion-selective carbon paste electrode for the potentiometric determination of active pharmaceutical ingredient : doctoral thesis
No full textU ovoj disertaciji opisan je detaljan tijek razvoja ionsko-selektivnog potenciometrijskog senzora na bazi paste od ugljikovog materijala za određivanje antimuskarinskog lijeka triheksifenidila. Osmišljeno je i u laboratoriju izrađeno tijelo elektrode kojim je omogućen niz mjerenja uz minimalnu potrošnju kemikalija koje sačinjavaju membranu. Pripravljeno je i testirano 235 membrana prosječne mase 101,6 ± 7,9 mg. Kao optimalna pokazala se membrana pripravljena od 40,6% grafita, 45,0% dibutilftalata kao veziva, 10,2% triheksifenidilovog tetrafenilborata kao ionsko-asocijacijskog kompleksa, 0,3% natrijevog tetrafenilborata kao ionskog aditiva te 3,9% reduciranog grafenovog oksida prethodno sintetiziranog iz grafita kao polazišnog materijala, a potom i karakteriziranog različitim analitičkim tehnikama. Pod optimiziranim eksperimentalnim uvjetima, elektroda je ostvarila Nernstovu promjenu potencijala od 58,9 ± 0,2 mV po dekadi promjene koncentracije uz koeficijent regresije od 0,9992. Pokazala je dobru selektivnost i ponovljivost, brzo vrijeme odziva (unutar 5 s) kao i širok raspon linearnog dinamičkog područja od 4,0×10 −7 do 1,0×10 −2 mol L -1 . Donja granica dokazivanja iznosi 2,5 × 10 −7 mol L -1 . Elektroda je primjenjiva u pH području od 2,4 do 5,2, a vrijeme života joj iznosi 19 dana. Analitičke primjene pripravljene kemijski modificirane elektrode na bazi paste od ugljikovog materijala dale su jako dobra iskorištenja u rasponu od 96,8 do 101,7% što ovu elektrodu svrstava u koristan analitički alat za brzo, jeftino i jednostavno određivanje triheksifenidila u čistim otopinama, otopinama farmaceutika odnosno u ljudskom urinu uz minimalnu predobradu uzorka. Razvijen je opći matematički model za metodu standardnog dodatka u potenciometriji prikazan segmentnim oblikom jednadžbe pravca.This dissertation analyzes the detailed course of development of an ion-selective potentiometric sensor based on a carbon paste electrode for the determination of the antimuscarinic drug trihexyphenidyl. An electrode body, which enables a series of measurements with minimal consumption of chemicals that make up the membrane, was designed and made in the laboratory. 235 membranes with an average mass of 101.6 ± 7.9 mg were prepared and tested. A membrane prepared from 40.6% graphite, 45.0% dibutyl phthalate as a binder, 10.2% trihexyphenidyl-tetraphenylborate as ion-associated complex, 0.3% sodium tetraphenylborate as an ionic additive and 3.9% reduced graphene oxide previously synthesized from graphite as a starting material, and then characterized by various analytical techniques, proved to be optimal. Under optimized experimental conditions, the electrode achieved a Nernst potential change of 58.9 ± 0.2 mV per concentration decade with a regression coefficient of 0.9992. It showed good selectivity and repeatability, fast response time (within 5 s) as well as a wide linear dynamic range from 4.0×10 −7 to 1.0×10 −2 mol L -1 . The lower limit of detection is 2.5×10 −7 mol L -1 . The electrode is applicable in the pH range from 2.4 to 5.2, and its lifetime is 19 days. Analytical applications of prepared chemically modified carbon paste electrode gave a very good recovery in the range of 96.8 to 101.7%, which makes this electrode a useful analytical tool for fast, cheap and easy determination of trihexyphenidyl in pure solutions, pharmaceutical suspensions and in human urine with minimal sample pretreatment. A general mathematical model presented by the intercept form of equation of a line has been developed within the standard addition method in potentiometry
Phenolic antioxidants of the Adriatic sea fennel flowers : diploma thesis
No full textObalni petrovac (Crithumum maritimum L.) je višegodišnja halofitna biljka iz porodice štitarki (Apiaceae). Raste na priobalnim podruĉjima Mediterana, Crnog mora te Atlantskog oceana. Kroz povijest se petrovac u narodnoj medicini koristio kao lijek, a danas predstavlja veliki potencijal za prehrambenu i farmaceutsku industriju zbog visokog sadržaja bioaktivnih komponenti. Cilj ovog rada bio je odrediti spektrofotometrijski udio ukupnih fenola i antioksidacijsku aktivnost ekstrakata cvijeta petrovca sa deset razliĉitih lokacija duž Jadranske obale, pomoću metode redukcije 2,2-difenil-1-pikrilhidrazil radikala (engl. 2,2-Diphenyl-1-picrylhydrazyl, DPPH) i metode odreĊivanja snage redukcije željeza (engl. Ferric Reducing Antioxidant Power, FRAP). Koncentracija klorogenske kiseline i njezinih derivata odreĊena je tekućinskom kromatografijom visoke djelotvornosti (engl. High Performance Liquid Chromatography, HPLC) sa UV/Vis detektorom. Rezultati su pokazali da cvjetovi petrovca sadrže visok udio ukupnih fenola te posjeduju izrazitu antioksidacijsku aktivnost što potvrĊuje potencijal iskoristivosti ne samo listova, već i cvjetova biljke. Najvišu koncentraciju fenolnih kiselina i antioksidacijsku aktivnost pokazao je uzorak sakupljen na podruĉju Senja, a najnižu uzorci sakupljeni na podruĉju Cavtata i Splita.Sea fennel (Crithmum maritimum L.) is a perennial halophytic plant of the umbellifers family (Apiaceae). It grows along the coastal areas of the Mediterranean, the Black Sea and the Atlantic Ocean. Throughout history, it has been used in folk medicine, but today it represents a great potential for the food and pharmaceutical industries due to its high content of bioactive compounds. The aim of this work was to determine by spectrometry the content of total phenolics and the antioxidant activity of sea fennel flower extracts from ten different locations along the Adriatic coast using the method of reduction of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assay. The concentrations of chlorogenic acid and its derivatives were determined using High Performance Liquid Chromatography (HPLC) with UV/Vis detector. The results showed that sea fennel flowers contain a high content of total phenolics and have good antioxidant activity, which confirms the potential of use not only the leaves, but also the flowers of sea fennel. The sample collected in Senj had the highest concentration of phenolic acids and antioxidant activity, while the samples collected in Cavtat and Split areas had the lowest concentration
Fluormetric study of the complexation of the phenantridine calixarene derivate with alkaline earthmetal cations : bachelor thesis
No full textU ovom završnom radu dan je teorijski uvid u supramolekulsku kemiju, kaliksarene i fluorimetriju te njihovu primjenu. Eksperimentalno je fluorimetrijskim titracijama istraživano koji od kationa elemenata iz zemnoalkalijske skupine ima najveći afinitet za stvaranje kompleksa s fenantridinskim derivatom kaliksarena5,11,17,23-tetra-tert-butil-25,27-bis(6-fenantridinilmetiloksi)-26,28- dimetoksikaliks[4]arenom, L. Zbog slabe topljivosti spoja L u polarnom otapalu, korišten je sustav otapala acetonitril/diklormeta, a od kationa su korišteni: magnezijev, kalcijev, stroncijev te barijev kation. Na temelju dobivenih eksperimentalnih podataka fluorimetrijskom titracijom zaključeno je da ligand L od svih spojeva najbolje kompleksira s kationom barija, odnosno prema njemu ima najveći afinitet pri čemu nastaje kompleks čija konstanta stabilnosti iznosi logK / dm 3 mol -1 = 4,90 ± 0,01.Od svih ispitivanih kationa, jedino za stroncijev kation s ligandom L fluorimetrijski nije uočeno stvaranje kompleksa. Utjecaj solvatacije i ionskog sparivanja imao je znatan utjecaj na afinitet kationa prema kompleksiranju s ligandom L, što se reflektira i u vrijednostima dobivenih konstanti stabilnosti odgovarajućih kompleksa, a pri tom veličina kationa ima važnu ulogu i za jačinu solvatacije i stvaranje ionskih parova, kao i za stabilnost kompleksa.This thesis provides a theoretical insight into supramolecular chemistry, calixarenes, and fluorimetry as well as their applications. It was experimentally investigated by fluorimetric titrations which of the cations of elements from the alkaline earth group has the highest affinity for the formation of a complexe with the phenanthridine derivative of calixarene 5,11,17,23-tetra-tert-butyl-25,27-bis(6- phenanthridinylmethyloxy)-26,28 -dimethoxycalix[4]arene, L. Due to the poor solubility of compound L in polar solvents, the solvent system acetonitrile/dichloromethane was used, while magnesium, calcium, strontium, and barium were used as cations. Based on the obtained experimental data by fluorimetric titration, it was concluded that, among the studied cations, ligand L has the highest affinity towards the barium cation, resulting in a complex whose stability constant is log K / dm 3 mol -1 = 4.90 + 0,01. Of all the tested cations, only for the strontium cation with the ligand L the formation of a complex was not observed fluorimetrically. The influence of solvation and ion pairing had a significant effect on the affinity of cations towards complexation with ligand L, which is reflected in the values of the obtained stability constants of the corresponding complexes, while the size of the cation plays an important role in the strength of solvation and formation of ion pairs, as well as in the stability of the complex
Recycling of waste packaging material : bachelor thesis
No full textMehaničko recikliranje je jedan od najučinkovitijih i najčešće korištenih pristupa za rješavanje problema plastičnog otpada. Iz inženjerske perspektive, izazovi u recikliranju polimera uključuju poteškoće u postizanju ujednačenih svojstava materijala zbog varijabilnosti kvalitete izvora i primijenjenog postupka oporabe. U ovom istraživanju, višestruko je ekstrudiran otpadni reciklirani ambalažni materijal kako bi se ispitali učinci termomehaničkog naprezanja na njegovu strukturu i toplinsku stabilnost. Ispitivanje je provedeno primjenom infracrvene spektroskopije s Fourierovom transformacijom (FT-IR) i termogravimetrijskom analizom (TGA). FT-IR spektri analiziranih uzoraka pokazuju da nakon trećeg ciklusa ekstrudiranja dolazi do značajnih promjena u strukturi, koje upućuju na oksidacijske i razgradne procese. TGA rezultati također ukazuju na značajnije pogoršanje toplinske stabilnosti materijala nakon treće ekstruzije. Očituje se razgradnjom reciklata u dva stupnja, pri čemu je temperatura početka razgradnje prvog stupnja niža u odnosu na početni reciklat. Dodatno, istraženi su struktura i toplinska svojstva mješavina izvornog PE-HD i reciklata petog ciklusa ekstrudiranja u masenim omjerima 30/70 i 50/50. Utvrđeno je da dodatak izvornog PE-HD-a smanjuje koncentraciju produkata razgradnje polimera i utječe na smanjenje gubitka mase u prvom razgradnom stupnju. Dobiveni pozitivan učinak miješanja izvornog i recikliranog polimera na svojstva reciklata ukazuje na potencijal reciklata za daljnje korištenje.Mechanical recycling is one of the most effective and widely used approaches to solving the problem of plastic waste. From an engineering perspective, challenges in polymer recycling include the difficulty in achieving uniform material properties due to the variability in source quality and recovery process applied. In this research, waste recycled packaging material was repeatedly extruded to investigate the effects of thermomechanical stress on its structure and thermal stability. The measurement was carried out using Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). FT-IR spectra of the analyzed samples show that after the third extrusion cycle, significant changes in the structure can be observed, which indicate oxidation and degradation processes. The TGA results also indicate a significant deterioration of the thermal stability of the material after the third extrusion. It can be concluded by the decomposition of recyclate in two degradation steps, where the onsent degradation temperature of the first step is lower compared to the initial recyclate. Additionally, the structure and thermal properties of mixtures of virgin PE-HD and recyclate from the fifth extrusion cycle in mass ratios of 30/70 and 50/50 were investigated. It was found that the addition of virgin PE-HD reduces the concentration of polymer degradation products and affects the reduction of mass loss of the first degradation step. The obtained positive effect of mixing the original and recycled polymer on the properties of the material indicates the potential of the recycled material for further use
SINTERING OF MAGNESIUM OXIDE OBTAINED FROM SEAWATER BITTERN : diploma thesis
No full textIzvršeno je ispitivanje utjecaja dodatka poli(vinil-alkohola) kao surfaktanta na veličinu i aglomeraciju čestica magnezijeva oksida dobivenog iz gorke morske vode. Proces taloženja magnezijeva hidroksida provodio se uz zasićenu vodu vapnenicu kao taložni reagens. Poli(vinil-alkohol) dodavao se u masenom omjeru (1:1,5) u odnosu na dobivenu masu magnezijeva hidroksida. Nakon procesa sušenja i kalcinacije uzorku kalciniranog magnezijeva oksida određena je raspodjela veličine čestica i kemijski sastav. Dobiveni rezultati pokazuju da dodatak surfaktanta pozitivno utječe na smanjenje veličine čestica, sprječava njihovo nakupljanje, ali ne sprječava potpuno stvaranje aglomerata. Dobiveni magnezijev oksid zatim je sinteriran pri temperaturama 1400°C, 1500°C i 1600°C uz vrijeme izotermnog zagrijavanja 2 sata. Iz dobivenih rezultata također se može uočiti da povećanje temperature sinteriranja ima pozitivan utjecaj na mikrostrukturu, gustoću, poroznost i smanjenje sadržaja bora u sinteriranim uzorcima magnezijeva oksida dobivenog iz gorke morske vode.The influence of the addition of poly(vinyl ̶ alcohol) as a surfactant on the size and agglomeration of magnesium oxide particles obtained from seawater bittern was tested. The magnesium hydroxide precipitation process was carried out using saturated limestone water as precipitation reagent. Poly(vinyl ̶ alcohol) was added in a mass ratio (1:1,5) in proportion to the magnesium hydroxide mass obtained. After the drying and calcination process, the particle size distribution and chemical composition of the calcined magnesium oxide sample were determined. The results show that the addition of surfactants has a positive effect on the reduction of particle size and prevents their accumulation, but not the complete formation of agglomerates. The magnesium oxide obtained was then sintered at temperatures of 1400 °C, 1500 °C and 1600 °C with an isothermal heating time of 2 hours. The results obtained show that increasing the sintering temperature has a positive effect on the microstructure, density, porosity and reduction of boron content in the sintered magnesium oxide samples from seawater bittern
Maturity and phenolic potential of pomegranate (Punica granatum L.) : bachelor thesis
No full textU ovom radu ispitivana su kemijska svojstva 45 različitih uzoraka soka šipka (14 hrvatskih sorti, 15 američkih sorti, 6 turskih sorti, 5 sorti s područja današnje Rusije, jedna španjolska sorta, dvije sorte divljeg šipka te dvije sorte nepoznatog porijekla) pri čemu je u uzorcima određen udio šećera, pH, ukupnih kiselina, indeks zrelosti te ukupni antocijani i fenoli. Rezultati su međusobno uspoređeni, s posebnim naglaskom na razlike u sastavu između hrvatskih sorti i sorti iz drugih regija. pH vrijednosti uzoraka kreću se u rasponu od 2,19 do 3,56 pri čemu je najniži pH izmjeren kod hrvatske sorte „Slatki tankokorac“ (2,19), a najviša vrijednost kod turske sorte „Fellahyemez“ (3,56). Najviši udio kiselina imali su uzorci soka divljeg šipka s Mljeta (3,84 g/100 mL) i iz Metkovića (3,24 g/100 mL). Najniži udio ukupnih fenola iznosio je 1989 mg GAE/L za sortu „Don Summer South“, dok je najviši određen u soku sorte „Comb’s sweet“ (5959 mg GAE/L) koja je imala i najviši udio antocijana (1201 mg M-3-g/L). Udio suhe tvari kretao se od 12,87 do 17,87 °Brix, dok se indeks zrelosti soka, određen kao omjer ukupne topljive suhe tvari i sadržaja ukupnih kiselina, kretao u rasponu od 3,99 (divlji šipak s Mljeta) do 102,5 (sorta „Thompson“).In this research work, the chemical properties of 45 different samples of pomegranate juice (14 Croatian varieties, 15 American varieties, 6 Turkish varieties, 5 varieties from the area of todays Russia, one Spanish variety, two wild pomegranate varieties, and two varieties of unknown origin) were analysed, whereby the sugar content, pH, total acids, maturity index, total phenolics and anthocyanins profile of the samples were determined. When comparing the results obtained, particular attention was paid to the differences in the composition of Croatian varieties and varieties from other regions. When determining the pH value, it was found that the pH values of the samples ranged from 2,19 to 3,56, with the lowest pH value measured in the Croatian variety „Slatki tankokorac“ (2,19) and the highest value in the Turkish variety „Fellahyemez“ (3,56). The highest acid content was found in wild pomegranate juice samples from Mljet (3,84 g/100 mL) and Metković (3,24 g/100 mL). The lowest content of total phenols was 1989 mg GAE/L in the „Don Summer South“ variety, while the highest content was found in the juice of the „Comb's sweet“ variety (5959 mg GAE/L), which also had the highest content of anthocyanins (1201 mg M-3-g/L). The dry matter ranged from 12,87 to 17,87 °Brix, while the maturity index, which is determined as the ratio between total soluble solids and total acid content, ranged from 3,99 (wild pomegranate from Mljet) to 102,5 („Thompson“ variety)
Impact of SBT impeller speed on copper sorption on zeolite : diploma thesis
No full textU ovom radu ispitivan je utjecaj brzine vrtnje turbinskog miješala s ravnim lopaticama tzv. SBT miješalo na sorpciju bakra na zeolitu NaX i utrošak snage miješanja pri konstantnoj temperaturi. Eksperiment je proveden u kotlastom reaktoru s razbijalima virova pri četiri različite brzine vrtnje miješala. Korištenjem Ritchievog modela i Weber-Morrisovog modela izvršena je kinetička analiza dobivenih kinetičkih eksperimentalnih podataka. Vrlo dobro slaganje dobivenih podataka s Ritchijevim modelom ukazuje na to da ispitivana reakcija prati kinetiku drugoga reda i da povećanjem brzine vrtnje SBT raste utrošak snage miješanja.The influence of the mixing speed of a turbine impeller with straight blades (SBT) of copper sorption on NaX zeolite and power consumption at constant temperature were investigated. The experiment was conducted in a batch reactor with baffles at four different impeller speeds. A kinetic analysis of the obtained kinetic experimental data was performed by the Ritchie model and the Weber-Morris model. Good agreement of the obtained data with Ritchie's model indicates that the reaction investigated follows the second-order kinetics and that the power consumption increases with increasing SBT speed
Influence of selenium on glucosinolate profile in rocket sprouts : master thesis
No full textGlukozinolati (β-tioglukozidni-N-hidroksisulfati) su velika grupa sekundarnih metabolita koji daju karakterističan gorki i oštri okus kupusnjačama te su njihovi razgradni produkti biološki aktivni spojevi. Razgradnja može biti termička, enzimska ili kemijska pri čemu nastaju brojni razgradni produkti kao što su tiocijanati i izotiocijanati. Klice rikule su nutritivno bogate, a prednost im je vrlo laki uzgoj. Klijanjem se nutrijenti u sjemenci razgrađuju na sastavne dijelove, razvija se klorofil i povećava se količina proteina, minerala i elemenata u tragovima. Dodatna prednost je da su bogate vitaminima, čiji se sadržaj povećava klijanjem, esencijalnim masnim kiselinama i vlaknima te imaju pozitivan učinak na organizam. Biljke nemaju potrebu za selenom i uglavnom ne podnose koncentracije veće od 10-100 μg/g suhe mase u tkivima, no vrste koje pripadaju obitelji Brassicaceae mogu akumulirati selen u tkivima i tolerirati koncentracije do 1000 μg/g suhe mase. Na taj način, biljke proizvode razne seleno metabolite koji mogu imati ulogu kao sredstva za sprječavanje raka. Istraživanja su pokazala da se u bočni lanac glukozinolata umjesto sumpora može ugraditi atom selena. U ovom diplomskom radu uzgojene su klice rikule te zalijevane otopinama selena različitih koncentracija (1; 2,5; 5; 7,5; 10 ppm). Razvoj biljaka praćen je tijekom 7 dana i jedino pri najvišoj koncentraciji selena nije došlo do razvoja biljke. Nakon sabiranja glukozinolati su izolirani ekstrakcijom 70%-tnim metanolom te analizirani UHPLC-DAD-MS/MS, a njihovi hlapljivi razgradni produkti su izolirani ekstrakcijom diklormetanom i identificirani GC-MS tehnikom. Identificirana su 4 glukozinolata: glukorafanin, glukoerucin, dimer glukosativina i 4-metoksiglukobrasicin, dok je GC-MS tehnikom identificiran erucin kao razgradni produkt glukoerucina.Glucosinolates (β-thioglucoside-N-hydroxysulfates) are a large group of secondary metabolites that give a characteristic bitter and pungent taste to cabbages and their degradation products are biologically active compounds. Degradation can be thermal, enzymatic, or chemical and it forms several degradation products such as thiocyanates and isothiocyanates. Rocket sprouts are nutritionally rich, and their advantage is very easy cultivation. By germination, the nutrients in the seed are broken down into their main components, chlorophyll develops and the amount of proteins, minerals and trace elements increases. An additional advantage is that they are rich in vitamins whose content increases with germination, essential fatty acids and fiber and have a positive effect on the body. Plants do not need selenium and generally do not tolerate concentrations higher than 10-100 μg/g dry weight in tissues, but species belonging to the Brassicaceae family can accumulate selenium in tissues and tolerate concentrations up to 1000 μg/g dry weight. In this way, plants produce various selenium metabolites that can play a role as a means of preventing cancer. Studies have shown that a selenium atom can be incorporated into the side chain of glucosinolates instead of sulfur. In this diploma thesis, rocket sprouts were grown and watered with selenium solutions of different concentrations (1; 2.5; 5; 7.5; 10 ppm). The development of the plants was monitored for 7 days, and only at the highest concentration of selenium the plant did not develop. After collection, glucosinolates were isolated by extraction with 70% methanol and analyzed by UHPLC-DAD-MS / MS, and their volatile degradation products were isolated by extraction with dichloromethane and identified by GC-MS technique. 4 glucosinolates were identified: glucoraphanin, glucoerucine, glucosatin dimer and 4-methoxyglucobrasicin, while GC-MS technique identified erucin which originate from degradation of glucoerucin
Seawater as a potential source of lithium : bachelor thesis
No full textObzirom na smanjenje mineralnih kopnenih rezervi, morska voda postaje dominantan izvor za iskorištavanje vrijednih metala i minerala. Budući da je element litij sastavni dio litij-ionskih baterija koje napajaju brojne elektroničke uređaje, a čija se potražnja svakim danom povećava proizvodnjom električnih automobila, svijet se suočava s potencijalnom nestašicom litija. U tu svrhu pokušavaju se pronaći i usavršiti alternativne metode njegova dobivanja iz morske vode, slane otopine zaostale nakon desalinizacije i gorke morske vode zaostale nakon dobivanja morske soli. U ovom radu napravljen je pregled dosadašnjih metoda dobivanja koje uključuju solarno isparavanje, adsorpciju, difuzijsku dijalizu, precipitaciju, ekstrakciju pomoću otapala i ionsku izmjenu. Također, predstavljena je metoda elektrodijalize u kojem se ioni prenose kroz polupropusnu membranu pod utjecajem električnog potencijala, a kojoj se teži budući da nudi obećavajuća rješenja njegova dobivanja. Buduća ispitivanja usmjerena su na povećanje trajnosti membrana i selektivnosti u svrhu primjene elektrodijalize za dobivanje litija i drugih minerala iz morske vode u komercijalne svrhe.Due to the decline of terrestrial mineral deposits, seawater is becoming the most important source for the extraction of valuable metals and minerals. Since the element lithium is a component of lithium-ion batteries that power numerous electronic devices, and their demand is increasing daily with the production of electric cars, the world is facing a potential lithium shortage. For this reason, efforts are being made to find and perfect alternative methods for extracting lithium from seawater, from brine remaining after desalination, and from the sea bittern remaining after sea salt extraction. This paper presents an overview of current extraction methods, which include solar evaporation, adsorption, diffusion dialysis, precipitation, solvent extraction, and ion exchange. A method of electrodialysis, in which ions are transported through a semipermeable membrane under the influence of an electric potential, was also presented and should be pursued as it offers promising solutions for their recovery. Future experiments will focus on increasing the durability and selectivity of membranes for electrodialysis applications to recover lithium and other minerals from seawater for commercial purposes
Kinetic analysis of thermal degradation of the PEO/ES composite : master thesis
No full textU ovom diplomskom radu istraživana je termogravimetrijska razgradnja kompozita PEO/ES različitih sastava pri tri različite brzine zagrijavanja u struji dušika. Temeljem vrijednosti karakterističnih temperatura kompozita PEO/ES dodatak mljevenih ljuskica jaja neznatno utječe na toplinsku stabilnost PEO-a. Primjenom izokonverzijskih Flyn- Wall-Ozawa i Friedman metoda izračunate su prosječne energije aktivacije (E a ) toplinske razgradnje navedenih kompozita. Na osnovu ovisnosti energije aktivacije toplinske razgradnje o konverziji (α) može se zaključiti da energija aktivacije u cijelom području konverzija ovisi o konverziji odnosno da je mehanizam složen. Dodatkom ljuskica jaja prosječna vrijednost energije aktivacije toplinske razgradnje se snižava, ali dodatak ne utječe na sam mehanizam razgradnje. Posebno se može izdvojiti kompozit PEO/ES sastava 90/10 koji sadrži najveći udio ljuskica jaja, zbog čega je vidljivo smanjenje E a te promjena ovisnosti E a o α što sugerira da dolazi do promjene mehanizma reakcije. Na temelju promjene ostatne mase u ovisnosti brzine zagrijavanja kompoziti sastava 99/1 i 90/10 razgrađuju se drugačijim mehanizmom u odnosu na kompozite ostalih sastava.In this thesis, the thermogravimetric decomposition of PEO/ES composites of different compositions was investigated at three different heating rates in a stream of nitrogen. Based on the values of the characteristic temperatures of the PEO/ES composite, the addition of ground eggshells slightly affects the thermal stability of PEO. Using isoconversional Flyn-Wall-Ozawa and Friedman methods, the average activation energy (E a ) of the thermal decomposition of the mentioned composites was calculated. Based on the dependence of the activation energy of thermal decomposition on the conversion (α), it can be concluded that the activation energy in the whole area of conversion depends on the conversion, suggesting that the mechanism is complex. With the addition of eggshells, the average value of the thermal decomposition activation energy is lowered, but the addition does not affect the decomposition mechanism itself. The composite PEO/ES composition 90/10, which contains the largest proportion of eggshells, can be singled out in particular, which is why there is a visible decrease in E a and a change in the dependence of E a on α, which suggests that there is a change in the reaction mechanism. On the basis of the change of the remaining mass in the dependence of the heating rate, the composites of the composition 99/1 and 90/10 are degraded by a different mechanism compared to the composites of the other compositions