Synthesis of PEDOT/ZnO Photocatalyst: Validation of Photocatalytic Activity by Degradation of Azo RR45 Dye Under Solar and UV-A Irradiation

To study the photocatalytic efficiency of wastewater treatment processes, the nanocomposites of conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) and ZnO nanoparticles were prepared by in-situ synthesis. ZnO is an excellent photocatalyst under UV light, but due to high band gap, photons of visible light have insufficient energy to excite electrons from valence to conductive band, which limits its activity under visible light and therefore practical usage is limited. The PEDOT conductive polymer was used to increase the photocatalytic activity of ZnO since conductive polymers are known as efficient electron donor and good electron transporters upon visible-light excitation. Polymerization of pure PEDOT and PEDOT/ZnO nanocomposites was carried out at varying monomer:oxidant ratio (1:2; 1:3; 1:5) with the ammonium persulfate (APS) used as the oxidant. Samples were characterized by FTIR spectroscopy, XRD analysis, SEM microscopy, UV-Vis spectroscopy and TG analysis. Photocatalytic activity was assessed through removal of C.I. Reactive Red 45 (RR45) azo dye under simulated Solar and UV-A irradiation. Photocatalysis was monitored by measuring discoloration of RR45 using UV/Vis spectroscopy. The results indicate that very low concentration of PEDOT conductive polymer in PEDOT/ZnO nanocomposite can significantly contribute to the efficiency of the photocatalytic process during wastewater treatment. This work is licensed under a Creative Commons Attribution 4.0 International License

Reduced Water Permeability of Biodegradable PCL Nanocomposite Coated Paperboard Packaging

In this work, we studied the properties of printed paperboard samples coated with biodegradable PCL polymer, which was considered to overcome the disadvantages (barrier properties) of a paper-based material. Additionally, the samples were coated with PCL modified with SiO2 and Al2O3 nanoparticles. The characterization of the coated paperboard (with print) samples was made by determination of water vapor transmission rate (WVTR), contact angle of water and its evolution over time, and mechanical and visual properties. The samples were also examined by SEM microscopy. The results show that PCL and PCL coatings modified with SiO2 and Al2O3 nanoparticles slow down the water vapor transmission rate when compared to the paperboard without coatings. The water contact angle measurements show an increase in hydrophobicity in paperboard coated with PCL-SiO2, while PCL-Al2O3 shows a decrease when compared to neat paperboard and paperboard coated with neat PCL. The studied coated samples also improve mechanical properties of paperboard while preserving the visual properties of print. This work is licensed under a Creative Commons Attribution 4.0 International License

Chemical Recycling of Postconsumer Poly(ethylene-terephthalate) Bottles – Depolymerization Study

Poly(ethylene-terephthalate), PET bottles waste was chemically recycled by glycolysis process. The glycolysis reaction was carried out at three temperatures 170, 180 and 190 °C in different time intervals (1, 3, 6 hours) with a weight ratio of ethylene glycol (EG) to PET 1 : 18 and the zinc acetate as a catalyst. The glycolysis reaction leads to formation of monomers bis(2 hydroxyethyl)terephthalate (BHET) and ethylene glycol as well as various types of PET oligomers. Depolymerization products were further characterized by infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). From the results it can be seen that remained PET products i.e. oligomers are thermally very stable and they are suitable for obtaining other polymers

Modification of PE/PP Polymer Blend Nanocomposites with EPR and EVA Copolymers

U ovom radu ispitivan je utjecaj nanopunila silicijeva dioksida (SiO2) kao i kompatibilizatora etilen/ propilen kopolimera (EPR) te etilen/vinil-acetata (EVA) na svojstva polimerne mješavine polietilen/polipropilen (PE/PP). Morfološke promjene pripremljenih uzoraka praćene su skenirajućom elektronskom mikroskopijom (SEM) i rendgenskom difrakcijom (XRD) te su određena fizikalno-mehanička svojstva i granični indeks kisika (LOI). Uspostavom privlačnih međudjelovanja poboljšava se adhezija između faza PE i PP, što ima za posljedicu finiju dispergiranost čestica u polimernim mješavinama. Što je dispergiranost nanopunila bolja povećava se postojanost polimerne mješavine i smanjuje gorivost polimernog materijala. Iz rezultata je vidljivo da je dodatkom kompatibilizatora i punila morfologija pripremljenih polimernih mješavina finija u usporedbi s čistim mješavinama. Dodatkom punila i kompatibilizatora povećava se elastičnost, što je posebno vidljivo kod uzoraka pripremljenih dvostupanjskim procesom ekstrudiranja gdje je prvo ekstrudirano punilo s matricom PE, a zatim su u drugom stupnju dodane preostale komponente mješavine. Rezultati određivanja graničnog indeksa kisika pokazali su da sastav ispitivanih polimernih mješavina ima neznatan učinak na gorivost.During the last decade, the use of polyolephinic polymers has been growing in a wide range of fields of applicability and the most widely used polymers are polyethylene and polypropylene. They can be processed separately to produce items with certain properties as well as in the form of blends, where special combinations of properties and price are intended. As it is known, polyethylene (PE) and polypropylene (PP) are incompatible and the weak interfacial bond strength between the phases directly linked to the blend morphology and results in poor mechanical properties. The properties of many polymer blends arise from the fine-scale structural arrangements or blend morphologies obtained during processing in addition to the proportion of each polymer type present. Compounding PE/PP blends with a single compatibilizer or their combination or some other additives as nanofiller, results in multi-component composites of great interest to research as they enable simultaneous improvement in the final properties of the blend. In addition, it is well known that the extrusion process has a significant effect on the dispersion of the filler in the blends. In this work, the mutual effect of the nanofiller silicium-dioxide (SiO2) and the compatibilizers ethylene-propylene copolymer (EPR) and ethylene-vinyl acetate copolymer (EVA) on the properties of blends based on polyethylene and polypropylene were studied. The morphology of the samples prepared with nanofiller and compatibilizers is much finer in comparison to the virgin blend. Better dispersion of nanofiller will result in better stability of the polymer blend and decrease in polymer flammability. The addition of the nanofiller and compatibilizers produced an increase in the elasticity especially for the samples prepared in the two-stage extrusion process where the nanofiller was first extruded with PE matrix and then with other polymers of the blends. SEM micrographs confirm finer morphology of samples prepared with compatibilizer and filler, which is the result of improved interactions between polymer components. The morphology also showed finer dispersion when EPR was used as compatibilizer, meaning that it has more effect in the investigated blends than EVA. Further, a slight increase in the limiting oxygen index was found in the blend prepared with EVA and nanofiller, which means that this blend has higher flame resistance, and it can be concluded that the nanofiller in combination with different amounts of the components in the formulations affects flammability

Characterization of Casein Fractions – Comparison of Commercial Casein and Casein Extracted from Cow’s Milk

Biopolymer casein was isolated from cow’s milk by acid coagulation, which was initiated by acetic acid and sodium acetate in the first, and hydrochloric acid in the second process. The casein isolated by acid coagulation, i.e. by first process, and commercial casein were separated on α-, β-, (α+κ)- and κ casein by urea fractionation. The aim of this study was to compare various properties of commercial casein fractions with casein fractions isolated from cow’s milk. The structure of casein and casein fraction samples were monitored by Fourier transform infrared spectroscopy (FTIR), and the obtained vibrational bands showed structural differences between isolated and commercial casein (presence of various amino acids), as well as their fractions. Differential scanning calorimetry (DSC) was used to determine glass transition temperature. The results showed that the glass transitions of the isolated and commercial casein were below room temperature (Tg = 2–30 °C) due to the destruction of the samples structure that provides molecules mobility and leads to a phase transition. Thermal degradation obtained by thermogravimetric analysis (TGA) of all samples occurred in multiple steps. From the results, it is evident that 5 mass % of the each sample degraded at significantly different temperatures (T95), and it can be concluded that isolated casein and its fractions showed better heat stability than commercial casein and its fraction

Characterization of Waste Poly(Ethylene-Terephthalate) after Alkali Treatment

U radu je proveden postupak obrade otpadnog PET-a prije samog recikliranja, koji osim sakupljanja i mljevenja uključuje i alkalno pranje PET-a. Postupak pranja PET-a proveden je pri sljedećim uvjetima: temperaturama od 70 i 75 °C te u različitom trajanju (15, 18, 21, 25 i 30 minuta). Uzorci otpadnog PET-a okarakterizirani su prije i nakon alkalnog pranja infracrvenom spektroskopijom (FTIR), diferencijalnom pretražnom kalorimetrijom (DSC) i metodom kontaktnog kuta. FTIR-spektroskopijom potvrđeno je nastajanje karboksilnih i hidroksilnih skupina na ṽ =3428 cm-1 tijekom alkalnog pranja. Smanjenje intenziteta karakterističnih vibracijskih vrpci (CO, COO i CH2) također ukazuje na depolimerizaciju PET-a odnosno nastajanje kraćih polimernih lanaca. DSC-om su određene temperature kristalizacije i taljenja te se iz dobivenih rezultata može zaključiti da je tijekom pranja došlo do djelomične depolimerizacije PET-a. Metodom kontaktnog kuta određena je površinska energija, a povećanje polarne komponente površinske energije ukazuje na postojanje skupina -OH i -COOH na površini PET-a. Općenito se može zaključiti da tijekom postupka alkalnog pranja dolazi do djelomične promjene u strukturi PET-a zbog utjecaja alkalnog medija koji uzrokuje hidrolizu tj. djelomičnu depolimerizaciju, ali je PET na kraju postupka pranja ipak prikladan za recikliranje i dobivanje recikliranog materijala zadovoljavajuće kvalitete.Poly(ethylene terephthalate), PET, recycling represents one of the most successful and widespread examples of polymer recycling. This material is fully recyclable and may be used for manufacturing new products in many industrial areas. Nevertheless, the excellent properties of PET needed for its many applications are also responsible for the difficult degradation of PET and an accumulation of polymer waste, which in turn creates serious environmental problems connected to littering and illegal landfilling or incineration. The main goal of this study was to examine the effect of alkali pretreatment on the properties of PET flakes. PET flakes were washed at two temperatures, 70 °C and 75 °C and in various time intervals of 15, 18, 21, 25, and 30 min. All samples were characterized by FTIR spectroscopy, differential scanning calorimetry and by contact angle measurements. The results showed that during the alkali treatment the partial depolymerization of PET was obtained, which resulted in the formation of various types of oligomers with hydroxyl and carboxyl end groups, which were the result of loss of high molecular structure. Decrease of intensity of characteristic vibrational bands (CO at 1717, COO at 1265 and CH2 at 722 cm-1) with extended time was observed (Figs. 1 and 2). Further on, the formation of hydroxyl groups at ṽ = 3428 cm-1 was also observed as a result of PET depolimerization during the alkali treatment, which behaviour was better visible for samples washed at 75 °C and with extended washing time (Fig 2b). During the DSC thermal analysis, multiple melting peaks were observed in some studied samples which could be linked to partial melting and re-crystallization of PET or to the occurrence of new polymer fractions of lower molecular mass (Figs. 3 and 4). It is evident that the contact angle of PET samples (Fig. 5) decreases in comparison to the PET 0, which points to the changes on the PET surface during the alkali treatment. Decrease in contact angle (which is measured with water) indicates an increase in surface hydrophilicity and increase in the number of present polar -OH and -COOH groups formed during the partial degradation. Also, the values of total surface energies and their polar and dispersive components indicate that during the alkali treatment the surface characteristics of PET flakes were slightly changed due to depolymerization (Table 3). Generally, it can be concluded that partial depolymerization of PET flakes occurs during the alkali treatment but the material retains its good properties and it is appropriate for the further recycling process

Modification of PE/PP Polymer Blend Nanocomposites with EPR and EVA Copolymers

During the last decade, the use of polyolephinic polymers has been growing in a wide range of fields of applicability and the most widely used polymers are polyethylene and polypropylene. They can be processed separately to produce items with certain properties as well as in the form of blends, where special combinations of properties and price are intended. As it is known, polyethylene (PE) and polypropylene (PP) are incompatible and the weak interfacial bond strength between the phases directly linked to the blend morphology and results in poor mechanical properties. The properties of many polymer blends arise from the fine-scale structural arrangements or blend morphologies obtained during processing in addition to the proportion of each polymer type present. Compounding PE/PP blends with a single compatibilizer or their combination or some other additives as nanofiller, results in multi-component composites of great interest to research as they enable simultaneous improvement in the final properties of the blend. In addition, it is well known that the extrusion process has a significant effect on the dispersion of the filler in the blends. In this work, the mutual effect of the nanofiller silicium-dioxide (SiO2) and the compatibilizers ethylene-propylene copolymer (EPR) and ethylene-vinyl acetate copolymer (EVA) on the properties of blends based on polyethylene and polypropylene were studied. The morphology of the samples prepared with nanofiller and compatibilizers is much finer in comparison to the virgin blend. Better dispersion of nanofiller will result in better stability of the polymer blend and decrease in polymer flammability. The addition of the nanofiller and compatibilizers produced an increase in the elasticity especially for the samples prepared in the two-stage extrusion process where the nanofiller was first extruded with PE matrix and then with other polymers of the blends. SEM micrographs confirm finer morphology of samples prepared with compatibilizer and filler, which is the result of improved interactions between polymer components. The morphology also showed finer dispersion when EPR was used as compatibilizer, meaning that it has more effect in the investigated blends than EVA. Further, a slight increase in the limiting oxygen index was found in the blend prepared with EVA and nanofiller, which means that this blend has higher flame resistance, and it can be concluded that the nanofiller in combination with different amounts of the components in the formulations affects flammability