Studij međudjelovanja komponenata u polimernim mješavinama poli(vinil-klorid)/poli(etilen-oksid)

Istraživana su međudjelovanja u mješavinama amorfnog poli(vinil-klorida) (PVC) i kristalastog poli(etilen-oksida) (PEO) različite molekulske mase u otopini, taljevini i čvrstom stanju. Istraživana je i toplinska postojanost mješavina bez i s dodatkom poli(etilen-glikola) (PEG). Podatci dobiveni viskozimetrijskim mjerenjima ukazuju da su PVC i PEO različitih molekulskih masa u otopini mješljivi u svim omjerima, pri čemu se interakcije (međudjelovanje) u mješavini smanjuju povećanjem molekulske mase PEO-a. Analizom spektara istraživanih mješavina snimljenih infracrvenom spektroskopijom s Fourierovom transformacijom (FT-IR) nije potvrđeno postojanje vodikove veze α-vodikovog atoma iz CHCl skupine PVC-a i kisikovog atoma iz PEO-a, kao ni utjecaj molekulske mase PEO-a na interakcije istraživanih mješavina. Nisu uočene značajnije promjene na FTIR spektrima koje bi ukazivale na utjecaj dodatka PEG-a na interakcije u istraživanim mješavinama. Temeljem postojanja dvaju staklišta koja odgovaraju staklištima čistih polimera i činjenici da dodatak PVC-a značajno ne snižava talište i kristalište, kao ni stupanj kristalnosti PEO-a u mješavini, može se zaključiti da su PVC i PEO različite molekulske mase djelomično mješljivi, ali samo pri znatnom udjelu PVC-a u mješavini. Nadalje, na osnovi postojanja dvaju staklišta na spektrima dobivenim dinamičko mehaničkom analizom (DMA) istraživanih mješavina koji se međusobno približavaju, može se potvrditi da su PVC i PEO različite molekulske mase djelomično mješljivi. Dodatak PVC-a mješavini PVC/PEO poboljšava njena mehanička svojstva. Dodatak PEG-a u mješavine PVC/PEO rezultira djelomičnom mješljivosti u cijelom području istraživanih sastava, a uočene interakcije su izraženije kod mješavina s PEO-om veće molekulske mase. Rezultati toplinske i termooksidacijske razgradnje istraživanih polimera i njihovih mješavina pokazali su da je PEO toplinski stabilniji od PVC-a i da se dodatkom PEO-a poboljšavaju toplinska i termooksidacijska stabilnost istraživanih mješavina. Dodatak PEG-a pogoršava toplinsku stabilnost mješavina PVC/PEO, odnosno ubrzava proces dehidrokloriranja PVC-a. Međutim, kod mješavina s PEO-om veće molekulske mase uočeno je da se dodatkom PEG-a poboljšava toplinsku stabilnost. Proces dinamičke termogravimetrijske (TG) razgradnje svih istraživanih mješavina odvija se po Avrami-Erofeevom kinetičkom modelu. Izračunate su konstante brzine (k) procesa dinamičke TG razgradnje istraživanih mješavina, a njihova ovisnost oeksperimentalnim temperaturama razgradnje ukazuje na toplinsku stabilnost mješavina. Dodatak PEO-a stabilizira sustav, što je u skladu sa zaključcima analize izotermne i dinamičke TG razgradnje u inertu. Dodatak PEG-a također snižava odgovarajuće vrijednosti konstante brzine reakcije.The interaction of amorphous poly(vinyl chloride) (PVC) in a blend with a semicrystalline poly(ethylene oxide) (PEO) of different molecular weights in solution, melt and solid state were investigated. The thermal stability of the blends and the effect of poly(ethylene glycol) (PEG) addition on the thermal stability, were invetigated as well. The results obtained by dilute solution viscosimetry measurements indicated that PVC and PEO of different molecular weights are miscible in the solution in all proportions, and that interactions in the blends decreases with the increase of PEO molecular weight. Analysis of the Fourier transform infrared spectroscopy (FT-IR) spectra of the investigated blends has not confirmed the existence of hydrogen bonds, as well as the effect of PEO molecular weight. There were no significant changes in the FT-IR spectra that would indicate the effect of PEG addition on interaction in the investigated blends. Based on the existence of two glass transition temperatures, which corresponds to the PVC and PEO glass transition temperatures and the small depression of the PEO melting and crystallization temperature, as well as the degree of crystallinity, it can be concluded that PVC and PEO of different molecular weight are only slightly miscible in the melt at elevated PVC content. Furthermore, based on the existence of two glass transition temperatures in the spectra that are approaching each other, obtained by dynamic mechanical analysis (DMA), it can be confirmed that the PVC and PEO of different molecular weight are partially miscible. PVC addition improves the mechanical properties of the blends. PEG addition resulted in partially miscibility and observed interactions are more pronounced in blends of PEO with higher molecular weight. Results of thermal and thermooxidative degradation of the investigated polymers and their blends showed that PEO is thermally more stable than PVC and that PEO addition improved thermal and thermooxidative stability of the blends. PEG addition deteriorates thermal stability of investigated blends and can accelerate the dehydrochlorination of PVC, respectively. However, PEG addition into blends of PEO with higher molecular weight improved the thermal stability of investigated blends. The process of non-isothermal thermogravimetry (TG) degradation of the investigated blends occurs through mechanism like those represented by the Avrami-Erofeev kinetic model. Rate constant (k) of the non-isothermal degradation were calculated, indicating blendthermal stability. The addition of PEO reduces the rate constant what is in accordance with results obtained from TG and DTG curves. PEG addition reduces the rate constant, as well

Recikliranje otpadnih PET boca: utjecaj reekstrudiranja na strukturu, toplinska svojstva i prividnu energiju aktivacije

In this work, post-consumer poly(ethylene terephthalate) (PET) bottles were gathered, separated from other materials, and re-extruded. In order to evaluate the effect of re-extrusion on the structure of PET, Fourier transform infrared spectroscopy was utilised. No significant effect of the re-extrusion process on the structure of the PET sample was noticed. Obtained samples were also characterised by differential scanning calorimetry (DSC) in order to determine characteristic thermal transitions of PET. DSC results indicated the influence of re-extrusion; extruded PET started to melt at lower temperatures, and the crystallisation of re-extruded PET took place at significantly higher temperatures in comparison to PET. Likewise, thermogravimetric analysis (TG) was used to evaluate the effect of re-extrusion process on the thermal stability of samples. TG analysis revealed that the re-extrusion process had no effect on the thermal stability of the investigated PET samples. Finally, the activation energy of thermal degradation of the investigated samples was calculated using iso-conversional Flynn-Wall-Ozawa and Friedman method. Consequently, higher activation energies were noticed for the re-extruded PET sample in comparison to the PET bottle sample, which is a good argument in support of PET bottle recycling.U ovom radu prikupljene su otpadne PET (poli(etilen-tereftalat)) boce, odvojene od ostalih materijala i reekstrudirane. S ciljem utvrđivanja utjecaja reekstrudiranja na strukturu PET-a primijenjena je infracrvena spektroskopija s Fourierovom transformacijom. Nije utvrđen značajan utjecaj procesa reekstrudiranja na strukturu PET-a. Uzorci su također karakterizirani primjenom diferencijalne pretražne kalorimetrije (DSC) s ciljem određivanja karakterističnih toplinskih prijelaza PET-a. Rezultati DSC analize ukazali su na to da se ekstrudirani PET započinje taliti pri nižim temperaturama, odnosno kristalizacija započinje pri znatno višim temperaturama u odnosu na PET. Termogravimetrijska analiza (TG) primijenjena je s ciljem procjene utjecaja reekstrudiranja na toplinsku stabilnost uzoraka. TG analizom potvrđeno je da reekstrudiranje nije utjecalo na toplinsku stabilnost istraživanih PET uzoraka. Konačno, primjenom izokonverzijskih Flynn-Wall-Ozawa i Friedman metoda analize izračunate su energije aktivacije toplinske razgradnje istraživanih uzoraka. U usporedbi s uzorkom PET boce, reekstrudirani PET uzorak pokazuje višu vrijednost energije aktivacije, što je dodatan argument u prilog recikliranja PET boca

Thermal Analysis of the Biodegradable Polymer PVA/PEO Blends

Poly(vinyl alcohol) (PVA) and poly(ethylene) oxide (PEO) are widely used water-soluble and biodegradable polymers that possesses high biocompatibility. In this work PVA/PEO blends were prepared via solution casting method, where the solvent was water. After drying, samples were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). Since DSC could not confirm the possible intermolecular interaction between PVA and PEO, infrared spectroscopy with Fourier transform (FT-IR) was utilized. Finally, the TG analysis revealed that degradation of PVA/PEO blends proceeds through tree stages, similar as neat PVA. Contrary, neat PEO thermally degrade through only one stage showing better thermal stability in comparison to PVA

Influence of Researchers on the Results of Kinetic Analysis of Thermal Degradation of Polymers

U ovom radu ispitivan je utjecaj istraživača na rezultate kinetičke analize neizotermne toplinske razgradnje četiri polimera. Analizirani polimeri imaju različite stupnjeve složenosti razgradnog procesa. Kinetičku analizu provelo je troje istraživača, jedan znanstveni savjetnik, jedan znanstveni suradnik te jedan doktorand, a svi su se koristili istim eksperimentalnim termogravimetrijskim podatcima te istim kinetičkim programom (Netzsch Thermokinetics Professional). Rezultati nedvojbeno pokazuju da istraživači imaju značajan utjecaj na rezultate kinetičke analize, budući da su procese neizotermne toplinske razgradnje svih uzoraka opisali različitim kinetičkim shemama i time različitim kinetičkim parametrima. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.In this paper, the influence of researchers on the results of kinetic analysis of non-isothermal thermal decomposition of four polymers was investigated. Four polymers having different degrees of complexity of the degradation process were analysed. The kinetic analysis was performed by three researchers: one scientific advisor with tenure, one research associate and one doctoral student, all of whom used the same experimental thermogravimetric data. Kinetic analysis was performed using the Netzsch Thermokinetics Professional program. The results unequivocally showed that the researchers have a significant influence on the results of kinetic analysis, since they described the processes of the non-isothermal thermal decomposition of all samples by different kinetic schemes, and thus by different kinetic parameters. This work is licensed under a Creative Commons Attribution 4.0 International License

Mehaničko recikliranje jednokratnih zaštitnih maski

Disposable protective face masks, the most used personal protective tools during the Covid-19 pandemic, have become a serious environmental concern that needs urgent attention. In this study, disposable protective face masks were disassembled into their components and mechanically recycled through extrusion. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to investigate the effect of recycling on the structure and morphology of the mask material. Microscopy revealed morphological differences among the layers of the mask. Differential scanning calorimetry and thermogravimetric analysis were used to characterise the thermal properties of the samples before and after recycling. Although the mechanical recycling process had minor effect on the thermal properties and stability of the mask material, thermal methods verified differences between the layers of the mask.Jednokratne zaštitne maske (DPM), kao najčešće upotrebljavani alat tijekom SARS-Covid-19 pandemije, postale su ozbiljan ekološki problem koji je potrebno riješiti. U ovom radu jednokratne zaštitne maske razdvojene su na sastavne komponente i mehanički reciklirane ekstrudiranjem. Infracrvena spektroskopija s Fourierovom transformacijom i pretražna elektronska mikroskopija primijenjene su za određivanje utjecaja recikliranja na strukturu i morfologiju materijala maske. Mikroskopija je ukazala na postojanje morfoloških razlika između slojeva maske. Toplinska svojstva istraživanih uzoraka prije i poslije recikliranja karakterizirane su primjenom diferencijalne pretražne kalorimetrije i termogravimetrijske analize. Iako su toplinske metode analize potvrdile razliku između slojeva maske, može se zaključiti da mehaničko recikliranje nije znatno utjecalo na toplinska svojstva i toplinsku stabilnost materijala maske

With food to health : proceedings of 11th International symposium

Proceedings contains 13 original scientific papers, 10 professional papers and 2 review papers which were presented at "10th International Scientific and Professional Conference WITH FOOD TO HEALTH", organised in following sections: Nutrition, Dietetics and diet therapy, Functional food and food supplemnents, Food safety, Food analysis, Production of safe food and food with added nutritional value

Ružička days : International conference 18th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Proceedings contains articles presented at Conference divided into sections: chemical analysis and synthesis, chemical and biochemical engineering, food technology and biotechnology, medical chemistry and pharmacy, environmental protection and meeting of young chemists