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Testing the activity of ceramic monolithic catalysts for the catalytic oxidation of BTEX compounds
No full textCilj ovog rada bio je ispitati učinkovitost različitih monolitnih katalizatora za katalitičku oksidaciju smjese aromatskih hlapljivih organskih BTEX spojeva. U BTEX spojeve ubrajaju se benzen, toluen, etilbenzen i ksilen. BTEX spojevi pripadaju hlapljivim organskim spojevima (VOCs) koji vrlo lako dospijevaju u okoliš i imaju štetan učinak na zdravlje ljudi zbog svojih toksičnih i kancerogenih svojstava. Katalitička oksidacija jedna je od dostupnih i često upotrebljavanih metoda za smanjenje koncentracije hlapljivih organskih spojeva. Nosači na koje su se nanosile katalitički aktivne komponente izrađeni su tehnikama aditivne proizvodnje, odnosno tehnikama proizvodnje rastaljenim filamentom i stereolitografije
(3D ispisani nosači). Za usporedbu korišteni su i komercijalni kordijeritni nosači izrađeni tehnikom ekstruzije. Kao katalitički aktivne komponente upotrijebljeni su miješani metalni oksidi mangana i željeza (MnFeOx), mangana i cinka (MnZnOx), mangana i bakra (MnCuOx), mangana i kroma (MnCrOx), mangana i kobalta (MnCoOx) te mangana i cinka (MnZnOx). Katalitička oksidacija provedena je u monolitnom reaktoru u uvjetima atmosferskog tlaka, u širokom rasponu temperature te uuz konstantan volumni protok reaktanata i zraka
(92 cm^3 min^-1). Za kriterij usporedbe učinkovitosti monolitnih katalizatora korištene su vrijednosti T10, T50 i T90 (°C) koje odgovaraju temperaturama za postizanje 10 %-tne,
50 %-tne i 90 %-tne konverzije BTEX spojeva. Na temelju usporedbe vrijednosti T10, T50 i T90 (°C) kordijeritnih nosača istih geometrijskih površina (29 cm^2) s nanesenim različitim katalitički aktivnim komponentama, uočeno je da je najučinkovitiji katalizator kordijeritni nosač s nanesenim MnFeOx kao katalitičkim slojem. Usporedbom vrijednosti T10, T50 i T90 (°C) za 3D ispisane monolitne nosače s nanesenim katalitičkim slojem MnFeOx zaključuje se da je najveća učinkovitost postignuta uz ZDP-FFF nosač, pri čemu je bila potrebna najniža vrijednost temperatura za postizanje 90 %-tne konverzije benzena.Testing the activity of ceramic monolithic catalysts for the catalytic oxidation of BTEX compounds The aim of this work was to examine the effectiveness of different monolithic catalysts for the catalytic oxidation of a mixture of aromatic volatile organic BTEX compounds. BTEX compounds include benzene, toluene, ethylbenzene and xylene. BTEX compounds belong to volatile organic compounds (VOCs) that easily reach the environment and have a harmful effect on human health due to their toxic and carcinogenic properties. Catalytic oxidation is one of the available and frequently used methods for reducing the concentration of volatile organic compounds. The carriers on which the catalytically active components were applied were made using additive manufacturing techniques, i.e. molten filament production techniques and stereolithography (3D printed carriers). For comparison, commercial cordierite supports made using the extrusion technique were also used. Mixed metal oxides of manganese and iron (MnFeOx), manganese and zinc (MnZnOx), manganese and copper (MnCuOx), manganese and chromium (MnCrOx), manganese and cobalt (MnCoOx) and manganese and zinc (MnZnOx) were used as catalytically active components. Catalytic oxidation was carried out in a monolithic reactor under conditions of atmospheric pressure, in a wide temperature range and with a constant volume flow of reactants and air (92 cm^3 min^-1). The T10, T50 and T90 values (°C) corresponding to the temperatures for achieving 10%, 50% and 90% conversion of BTEX compounds were used as a criterion for comparing the effectiveness of monolithic catalysts. Based on the comparison of the T10, T50 and T90 values (°C) of cordierite supports with the same geometric surfaces (29 cm^2) with different catalytically active components applied, it was observed that the most effective catalyst is the cordierite support with applied MnFeOx as a catalytic layer. By comparing T10, T50 and T90 values (°C) for 3D printed monolithic supports with a deposited MnFeOx catalytic layer, it is concluded that the highest efficiency was achieved with the ZDP-FFF support, while the lowest temperature value was required to achieve 90% benzene conversion
Photochemical transformations of diverse biologically active resveratrol derivatives in batch and flow reactor
No full textRezveratrol je stilbenoidni polifenol s različitim antioksidativnim, antitumorskim, neuroprotektivnim i kardioprotektivnim svojstvima, a zbog niske bioraspoloživosti, razvijaju se njegovi biološki aktivni derivati koji pokazuju značajan antioksidativni potencijal i inhibicijsku aktivnost za enzime kolinesteraze, što je dokazano nižim IC50 vrijednostima u odnosu na standardni inhibitor galantamin. U ovom su radu Wittigovom reakcijom sintetizirani heteroaromatski derivati rezveratrola koji su poslužili kao početni spojevi 1-5 za daljnje fotokemijske transformacije u šaržnom i protočnom reaktoru. Fotokemijske transformacije provedene su izravnim osvjetljavanjem početnih spojeva na različitim valnim duljinama ili uz prisutstvo porfirinskog fotokatalizatora s četiri različite LED lampe. Osim valne duljine i fotokatalizatora, u protočnom se reaktoru još mijenjalo vrijeme zadržavanja i temperatura.
Iz rezultata je najviše vidljivo dobivanje cikličkih produkata i trans-cis izomerizacija, a računalnim istraživanjem fotoreaktivnosti početnog spoja 1 utvrđeni su glavni putevi njihova dobivanja. Uspoređujući produktivnost i selektivnost reakcije te iskorištenja fotoprodukata, zaključilo se kako je protočni reaktor svakako bolji izbor u odnosu na šaržni reaktor.Resveratrol is a stilbenoid polyphenol with various antioxidant, antitumor, neuroprotective and cardioprotective properties, and due to low bioavailability, its biologically active derivatives are being developed. These analogs show significant antioxidant potential and inhibitory activity for the cholinesterase enzyme, which is proven by lower IC50 values compared to standard inhibitor galantamine. In this work, heteroaromatic derivatives of resveratrol were synthesized by the Wittig reaction, which served as starting compounds 1-5 for further photochemical transformations in batch and flow reactors. Photochemical transformations were carried out by direct illumination of the initial compounds at different wavelengths or in the presence of a porphyrin photocatalyst with four different LED lamps. In addition to the wavelength and the photocatalyst, the residence time and temperature also varied in the flow reactor. The results mainly show cyclization products as well as trans-cis isomerization, and computational study of the photoreactivity of the starting compound 1 determined the main paths of their obtaining. Comparing the productivity and selectivity of the reaction and yields of photoproducts, it was concluded that the flow reactor is a better choice compared to the batch reactor
Properties and application of wood-plastic composites
No full textDrvno-plastični kompoziti izrađuju se od plastičnog materijala kao matrice i drva kao punila. Primjena drvno-plastičnih kompozita sve je veća zbog njihovih dobrih konačnih svojstava. Drvo ugrađeno u plastičnu matricu poboljšava mehanička svojstva dok plastika u
drvno-plastičnim kompozitima smanjuje bubrenje u vodi. Različiti drvni i poljoprivredni ostaci povezani s polimernom matricom, osim što daju kompozit dobrih svojstava, pomažu u zbrinjavanju otpada. U posljednje vrijeme, sve je više nastojanja da se postigne učinkovito recikliranje otpadnih polimernih i drugih materijala. Jedan od prikladnih načina zbrinjavanja polimernog otpada i različitih drvnih, tj. općenito celuloznih ostataka upravo su
drvno-plastični kompoziti. Ovaj rad analizira različite postupke pripreme i primjene
drvno-plastičnih kompozita kao i njihova svojstva.Wood-plastic composites are prepared of plastic material as a matrix and wood as a filler. The use of wood-plastic composites is increasing due to their good final properties. Wood embedded in a plastic matrix improves mechanical properties, while plastic in wood-plastic composites reduces swelling in water. Various wood and agricultural residues combined with the polymer matrix, providing a composite with good properties, help also in a waste treatment. Recently, there has been an increasing effort to achieve efficient recycling of waste polymers and other materials. Wood-plastic composites are one of the suitable ways to use polymer waste as well as various wood or cellulose residues. This paper analyzes various methods of preparation, properties and application of wood-plastic composites
Artificial neural networks in chemical engineering
No full textTopljivost različitih organskih spojeva u vodi je važna za razvoj lijekova u farmaceutskoj i novih kemijskih spojeva u kemijskoj industriji. Pomoću umjetnih neuronskih mreža možemo predvidjeti kako će različiti organski spojevi biti topljivi u vodi na temelju njihovih karakteristika i na taj način odlučiti kakva vrsta spoja je potrebna za projekte. Umjetne neuronske mreže djeluju na sličan način kao ljudski mozak. Umjetne neuronske mreže u kemijskom inženjerstvu se koriste za predviđanje rezultata nepoznatih vrijednosti nakon procesa treniranja. U ovom radu fokus je na primjeni umjetnih neuronskih mreža za predviđanje topljivosti organskih spojeva u vodi.Solubility of various organic compounds in water is very important for drug development in pharmaceutical and the creation of new chemical compounds in the chemical industry. Using artificial neural networks, we can anticipate how the solubility of different organic compounds will be based on the characteristics of said compounds and which type of compound is needed for specific projects. Artificial neural networks work on a similar principle to the human brain, enabling the prediction of unknown values after the training process.
This paper focuses on the use of artificial neural networks to predict the solubility of organic compounds in water
The effect of the broom fibres content on the mechanical and morphological properties of composites based on thermoplastic polymers
No full textU posljednjih nekoliko godina primjećen je porast interesa za komercijalnom upotrebom kompozita na osnovi prirodnih vlakana, odnosno biokompozita. Interes za ovim materijalima javlja se uslijed zabrinutosti ljudi zbog potencijalne štetnosti i problema zbrinjavanja otpada koji nastaje upotrebom materijala na osnovi neobnovljivih izvora energije. Prirodna vlakna predstavljaju održive materijale, lako dostupne u prirodi, s nizom prednosti poput niske cijene, male težine, obnovljivosti, biorazgradivosti te visokih specifičnih svojstava. Istraživanje je usmjereno na ispitivanje mehaničkih i morfoloških svojstava kompozita termoplastičnog polimera i vlakana brnistre. Kao termoplastični polimeri za pripravu kompozita korišteni su polikarbonat (PC), akrilonitril butadien stiren (ABS) i polipropilen (PP) te vlakna brnistre
u udjelima od 0, 5, 10, 15 i 20 mas. %.In the last few years, there has been a growing interest in the commercial use of composites based on natural fibers, i.e. biocomposites. Interest in these materials stems from the growing concern of people about potential harm and the problem of waste disposal arising from the use of materials based on non-renewable sources of energy. Natural fibers represent sustainable materials, easily available in nature, with several advantages such as low cost, light weight, renewability, biodegradability and high specific properties.
The mechanical and morphological properties of the composite of thermoplastic polymer and Spartium junceum L. fibers were investigated. Polycarbonate (PC), acrylonitrile butadiene styrene (ABS) and polypropylene (PP) were used as thermoplastic polymers for composite preparation as well as Spartium junceum L in the content of 0, 5, 10, 15 and 20 wt. %
Testing the self-healibility of conductive films based on poly(3,4-ethylenedioxythiophene)
No full textOtkrivanje vodljivosti u određenim vrstama polimera otvorilo je nove mogućnosti u znanstvenim istraživanjima, značajno povećavši interes za ovo područje. Elektrovodljivi polimeri, sa svojim jedinstvenim optičkim i električnim svojstvima predstavljaju izuzetno svestrane organske materijale. Njihova kemijska stabilnost, mehanička fleksibilnost, izvrsna obradivost, podesiva vodljivost i biokompatibilnost omogućuje široku primjenu u elektronici i mikroelektronici, medicini, biotehnologiji, senzorskim tehnologijama te fleksibilnoj elektronici. Posebno se ističe poli(3,4-etilendioksitiofen) (PEDOT), koji se zbog svoje visoke vodljivosti smatra jednim od najvažnijih predstavnika elektrovodljivih polimera. Kopolimerizacijom PEDOT-a s drugim polimerima moguće je značajno modificirati i prilagoditi svojstva konačnog proizvoda, što omogućuje razvoj inovativnih rješenja za suvremene tehničke izazove, osobito u području nosive elektronike. Svrha ovog rada je istražiti samozacjeljivost elektrovodljivih filmova na bazi PEDOT-a, sintetiziranih iz EDOT i ThBr monomera te termoplastičnog elastomera SEBS-a, koji doprinosi povećanju elastičnosti polimerne mješavine.
Poli(akrilat-uretan) (PAU) je ugrađen u lanac PEDOT-a naknadnom radikalskom polimerizacijom putem prijenosa atoma (ATRP). Zahvaljujući vodikovim vezama, PAU omogućuje fizikalno umrežavanje, čime se postiže svojstvo samozacjeljivanja filmova. Dobiveni produkti analizirani su pomoću infracrvene spektroskopije s Fourierovom transformacijom (FTIR) te pomoću sonde s 4 točke (4PP), a provedena su i ispitivanja stabilnosti te ispitivanja mehaničkih svojstavaIzrađeni polimerni filmovi pokazali su izvrsna mehanička svojstva, istezljivost, stabilnost, električnu provodnost i sposobnost samozacjeljivanja, što im otvara mogućnost primjene u nosivoj elektronici. Potvrđena električna vodljivost pruža priliku za daljnju optimizaciju ovih filmova u tu svrhu.The discovery of conductivity in certain types of polymers has opened new possibilities in scientific research, significantly increasing interest in this field. Conductive polymers, with their unique optical and electrical properties, represent exceptionally versatile organic materials. Their chemical stability, mechanical flexibility, excellent processability, tunable conductivity, and biocompatibility enable wide application in electronics and microelectronics, medicine, biotechnology, sensor technologies, and flexible electronics. Particularly noteworthy is poly(3,4-ethylenedioxythiophene) (PEDOT), which is considered one of the most important representatives of conductive polymers due to its high conductivity. By copolymerizing PEDOT with other polymers, it is possible to significantly modify and tailor the properties of the final product, allowing the development of innovative solutions for contemporary technical challenges, especially in the field of wearable electronics. The purpose of this study is to investigate the self-healing properties of conductive films based on PEDOT, synthesized from EDOT and ThBr monomers, and thermoplastic elastomer SEBS, which contributes to the increased elasticity of the polymer blend. Poly(acrylate-urethane) (PAU) was incorporated into the PEDOT chain via subsequent atom transfer radical polymerization (ATRP). Due to hydrogen bonding, PAU enables physical cross-linking, thereby achieving the self-healing property of the films. The obtained products were analyzed using Fourier-transform infrared spectroscopy (FTIR) and a four-point probe (4PP), and stability and mechanical property tests were also performed. The fabricated polymer films demonstrated excellent mechanical properties, stretchability, stability, electrical conductivity, and self-healing capability, which opens up opportunities for their application in wearable electronics. The confirmed electrical conductivity provides an opportunity for further optimization of these films for this purpose
Bioremediation of water polluted with polystyrene microplastic particles using bacterial culture Pseudomonas alcaligenes
No full textRazgradnja pogrešno zbrinutog ili nezbrinutog polimernog otpada u okolišu dugotrajan je proces s neželjenim i zabrinjavajućim produktima. Na taj način, uslijed klimatskih utjecaja, dolazi do slabljenja fizikalnih i kemijskih svojstava plastičnog materijala, ali i njegova propadanja što pak otvara mogućnost migracije zrakom ili vodom do živih organizama. Takve čestice, kojima se još uvijek ne zna točan rizik, a predstavljaju veliku zabrinutost, nazivamo mikroplastika (MP). MP kategoriziramo kao polimerne čestice veličine manje od 5 mm. Glavni fokus do sada bio je na ekotoksikološkim istraživanjima, a sada i na pokušaj dizajna alternativnog sustava za bioremedijaciju glavnih sastavnica okoliša u svrhu zaštite od potencijalnih štetnih učinaka na ekosustave. Cilj ovog rada bio je razgradnja MP-a polistirena (PS) i poli(vinil-klorida) (PVC) pomoću bakterijske kulture Pseudomonas alcaligenes u vodenom okolišu i evidentiranje potencijalnih štetnih učinaka nepoznatih metabolita koji pritom mogu nastati. Primijenjen je puni faktorski plan (eng. Full factorial design) za postavljanje pokusa s tri čimbenika na tri razine. Glavni ispitivani čimbenici u pokusu s PS-om bili su veličina čestica, broj okretaja i optička gustoća (OG), a s PVC-om pH-vrijednost, koncentracija MP-e i OG. Pokus se provodio tijekom 30 dana, a uzorci za analizu izuzimani su u 0., 3., 7., 14., 21. i 30. danu. U navedenim danima pratila se koncentracija organskog i anorganskog ugljika, OG, CFU i nastajanje nusprodukata procesa HPLC-MS analizom. Analiza promjena u strukturi čestica PS-a i PVC-a nakon pokusa provedena je FTIR-ATR spektroskopijom, a toksičnost filtrata određena je bakterijom V. fischeri. Svim navedenim analizama potvrđeno je da u procesu uistinu dolazi do promjena u strukturi plastike što indicira da se ona biorazgrađuje. Analizom varijance (ANOVA) potvrđeno je da je model značajan u oba pokusa, a da su optimalni uvjeti za provođenje pokusa s PS-om: broj okretaja od 180 o/min, veličina MP-a 203 μm i OG 0,27. U pokusu s PVC-om idealni su uvjeti pH 7, γMP 50 mg/L i OG 0,3.Decomposition of incorrectly disposed or unmanaged polymer waste in the environment is a long-term process with unwanted and worrying products. In this way, climatic influences enable weakening of physical and chemical properties of plastic material but also its decay, which in turn opens the possibility of migration by air or water to living organisms. Such particles, whose exact risk is still unknown and of great concern, are called microplastics (MP). They are categorized as polymer particles smaller than 5 mm in size. The main focus so far has been on ecotoxicological research, but now also on trying to design an alternative system for bioremediation of the main components of the environment in order to protect the ecosystems against potential adverse effects. The aim of this study was to biodegrade polystyrene and polyvinyl chloride MP by use of Pseudomonas alcaligenes bacterial culture in an aquatic environment and to record the potential adverse effects of unknown metabolites that may occur. A Full factorial design was applied to set up a three-factor experiment on three levels. The main factors in the PS experiment were particle size, number of revolutions, and optical density (OG) and with PVC there were pH value, MP concentration and optical density (OG). The experiment was conducted for 30 days and samples were taken on the 0., 3., 7., 14., 21. and 30. day. In aformentioned days we monitored the concentration of organic and inorganic carbon, OG, CFU and by-products formation with HPLC-MS analysis. Analysis of changes in the PS and PVC particle structure after the experiment was carried out by FTIR-ATR spectroscopy and the toxicity of the filtrate was determined by use of bacteria V. fischeri. All the aforementioned analyzes confirmed that the process actually causes changes in the structure of the plastic, which indicates that it biodegrades. Analysis of variance (ANOVA) confirmed that the model is significant in both experiments and that the optimal conditions for conducting experiments with PS are: number of revolutions of 180 rpm, MP size 203 μm and OG 0,27. In the experiment with PVC, the ideal conditions are pH 7, γMP 50 mg/L and OG 0,3
The influence of pollen on the properties of polymer hydrogels
No full textU ovom su radu pripremljeni hidrogelovi na bazi polimera poli(vinil-alkohola) uz dodatak peludi. Kao komponenta za pripremu hidrogelova, korišten je i natrijev alginat. Hidrogelovi su vrsta materijala pogodna za primjenu u medicini jer su netoksični, imaju mogućnost upijanja i zadržavanja velike količine vode te se mogu regenerirati. Hidrogelovi su pripremljeni metodom zamrzavanje/odmrzavanje. Za karakterizaciju hidrogelova, koristile su se različite metode. Određen im je udio vode, stupanj bubrenja, antimikrobna i mehanička svojstva. Vodljivost hidrogelova određena je elektrokemijskom impedancijskom spektroskopijom (EIS), a za karakterizaciju je korištena i infracrvena spektroskopija s Fourierovom transformacijom (FTIR). Rezultati mjerenja pokazali su da se stupanj bubrenja povećava dodatkom peludi u hidrogelove što predstavlja potencijal primjene hidrogelova s peludi kao obloga i dijelova zavoja za rane. Pokazalo se i da pelud posjeduje antimikrobnu aktivnost. Rezultati mehaničkih ispitivanja pokazali su da hidrogelovi s peludi imaju višu vrijednost lomnog produljenja od čistog polimernog hidrogela što ih čini postojanijima za rukovanje i upotrebu.In this thesis, hydrogels based on the polymer polyvinyl alcohol, with the addition of pollen, were prepared. The preparation of hydrogels also included sodium alginate as a component. Because of their non-toxicity, ability to absorb and keep large amounts of water, and
self-regeneration abilities, hydrogels are a material that is suitable for medical use.
The hydrogels were prepared by the freezing/thawing method. The characterization of prepared hydrogels required different tools and techniques. The hydrogels were characterized by determining their water content, swelling behaviour as well as antimicrobial and mechanical properties. Electrochemical impedance spectroscopy (EIS) was used to measure the conductivity of prepared hydrogels. Fourier transform infrared spectroscopy (FT-IR) was also used for characterization. The measurement results showed that adding pollen to the hydrogels increased the degree of swelling. This represents the potential for applying hydrogels with pollen as medical coatings and parts of wound dressings. It has also been shown that pollen has antimicrobial activity. The results of mechanical tests showed that hydrogels with pollen have a higher value of elongation at break than pure polymer hydrogels, which makes them more stable for handling and use
Effect of multiple mechanical recycling process on properties of polypropylene
No full textPolimerni materijali prisutni su u svim sferama ljudskoga života. Njihovom upotrebnom nastaju i velike količine polimernog otpada koji je potrebno odgovarajuće zbrinuti kako ne bi predstavljao opasnost za ljude i okoliš. Mehaničko recikliranje pokazalo se kao učinkovit postupak prerade termoplastičnih polimernih materijala kojim je omogućeno njihovo ponovno korištenje u različite svrhe. Iako termoplasti teoretski imaju praktično neograničenu mogućnost višestrukog recikliranja bez gubitka svojstava, zbog nečistoća koje se mogu naći u polimernom materijalu potencijalno ipak može doći do negativnog utjecaja na svojstva.
U ovom radu, upravo zbog prethodno navedenog, praćen je utjecaj višestrukih ciklusa mehaničkog recikliranja na svojstva polipropilena (PP). Uzorci čija su se svojstva pratila pripremljeni su miješanjem čistog PP, industrijski recikliranog PP, željezovog(III) oksida te metaliziranog PP dobivenog od ambalažnog otpada. Nakon pripreme smjesa provedena su četiri ciklusa mehaničkog recikliranja ekstudiranjem. U svrhu praćenja utjecaja višestrukih ciklusa mehaničkog recikliranja na svojstva provedena je karakterizacija različitim metodama. Diferencijalnom pretražnom kalorimetrijom (DSC) određene su temperature taljenja (Tm) i kristalizacije (Tc) te toplinski tokovi uslijed endotermnih (ΔHm) i egzotermnih (ΔHc) promjena. Na temelju određenog, izračunat je i stupanj kristalnosti (Xc). Skenirajućim elektronskim mikroskopom praćene su promjene u morfologiji i sastavu ispitivanih uzoraka. Nadalje, određen je maseni protok taljevine (MFR), a na kraju je uslijedilo ispitivanje mehaničkih svojstava uzoraka pomoću mehaničke kidalice. Svojstva su se pratila nakon svakog ciklusa recikliranja. Rezultati istraživanja pokazali su da višestruko mehaničko recikliranje nema značajnog negativnog utjecaja na kemijsku strukturu i svojstva PP koja bi onemogućila njegovu primjenu tj. mehaničko recikliranje pokazalo se kao učinkovita metoda oporabe PP.Polymeric materials are present in all spheres of human life. Their use generates large amounts of polymer waste, which must be properly managed to prevent it from posing a hazard to humans and the environment. Mechanical recycling has proven to be an effective way to process thermoplastic polymer materials, allowing their reuse for various purposes. Although thermoplastics theoretically have a virtually unlimited potential for multiple recycling cycles without loss of properties, impurities that may be present in the polymer material can potentially have a negative impact on properties. In this study, the effect of multiple cycles of mechanical recycling on the properties of polypropylene (PP) was investigated for this very reason. The samples whose properties were studied were prepared by mixing pure PP, industrially recycled PP, iron(III) oxide and metallized PP from packaging waste. After the mixtures were prepared, four cycles of mechanical recycling by extrusion were performed.
In order to monitor the effects of multiple cycles of mechanical recycling on the properties, characterization was performed using different methods. Differential scanning calorimetry (DSC) was used to determine the melting temperature (Tm) and crystallization temperature (Tc), as well as the heat flows due to endothermic (ΔHm) and exothermic (ΔHc) changes.
The degree of crystallinity (Xc) was also calculated based on the data. Changes in the morphology and composition of the tested samples were observed by scanning electron microscopy. In addition, the melt flow rate (MFR) was determined and finally the mechanical properties of the samples were tested using a universal testing machine. The properties were monitored after each recycling cycle. The research results showed that multiple mechanical recycling cycles did not have significant negative effects on the chemical structure and properties of PP that would hinder its application. Mechanical recycling has been shown to be an effective method for the recovery of PP
Synthesis and spectroscopic characterization of novel imidazo[4,5-b]pyridines as potential sensors for pH in solutions
No full textU ovom radu sintetizirane su Schiffove baze imidazo[4,5-b]piridina. Kako bi se priredili željeni derivati imidazo[4,5-b]piridina 10-12 korištene su klasične reakcije organske sinteze. Sinteza željenih spojeva započeta je sintezom N-metil-3-nitropiridin-2-amina 3 koji je priređen reakcijom 2-klor-3-nitropiridina 1 s metilaminom u etanolu uz zagrijavanje reakcijske smjese. Redukcijom, zagrijavanjem etanolne otopine spoja 3 s SnCl2×2H2O, priređen je
2-N-metilpiridin-2,3-diamin 4. Iz spoja 4 i p-aminobenzojeve kiseline 5, priređen je glavni amino-supstituirani prekursor 6. Schiffove baze 10-12 priređene su iz prekursora 6 i odgovarajućih aldehida 7-9, u apsolutnom etanolu uz dodatak octene kiseline. Strukture priređenih spojeva potvrđene su 1H i 13C NMR spektroskopijom, a spojevi 10-12 dodatno su okarakterizirani UV/Vis spektroskopijom u otapalima različite polarnosti. Ispitana je i mogućnost primjene Schiffovih baza 10-12 kao optičkih pH senzora, praćenjem promjene intenziteta apsorbancije spojeva ovisno o različitim pH vrijednostima pufera. Provedenim ispitivanjima utvrđena je mogućnost korištenja priređenih Schiffovih baza 10-12 kao optičkih pH senzora.The aim of this work was the sythesis of imidazo[4,5-b]pyridine Schiff bases. Classic organic reactions were used for preparation of novel imidazo[4,5-b]pyridine derivatives 10-12. Their synthesis began with synthesis of N-methyl-3-nitropyridin-2-amine 3, which was prepared from 2-chloro-3-nitropyridine 1 and methylamine in ethanol by heating the reaction mixture. Within the reduction of ethanol solution of compound 3 and SnCl2×2H2O, the
2-N-methylpyridine-2,3-diamine 4 was prepared. Furthermore, from compound 4 and p-aminobenzoic acid 5, the main amino substitued precursor 6 was prepared. Schiff bases 10-12 were prepared from precursor 6 and aldehydes 7-9 in absolute ethanol with an addition of acetic acid. Structures of prepared compounds were confirmed with 1H and 13C NMR spectroscopy. Schiff bases 10-12 were also characterized by UV/Vis spectroscopy in solvents with different polarity. The possibility of using prepared Schiff bases 10-12 as optical pH sensors was also tested by tracking change in absorbance intensity of the compounds depending on the different pH values of buffer solutions. Conducted experiments have proven possibility of using prepared Schiff bases 10-12 as optical pH sensors