Search

This study was aimed to prepare material with high porosity and photocatalytic activity by immobilization of TiO2 nanoparticles (NPs) onto poly(lactic acid) (PLA) aerogels. PLA aerogels were prepared in three steps: (1) dissolution of polymer in chloroform at 22 °C, (2) chloroform replacement with ethanol, and (3) supercritical CO2-drying at pressure 19 MPa and temperature 39 ºC. Immobilization of TiO2 NPs was performed by in situ and ex situ methods. Obtained samples were characterized using SEM, EDX, and FTIR analysis. Photocatalytic activity of developed material was tested by following decolorization of dye C.I. Acid Orange 7 in water solution. It was shown that the morphology of PLA aerogels was slightly affected by TiO2 NPs immobilization. PLA aerogels with TiO2 NPs immobilized by ex situ method sustained floatability during test period and provided a complete decolorization of dye solution after 330 minutes of illumination. High photocatalytic activity of the sample was preserved within three repeated cycles of dye decolorization., Cilj ovog istraživanja bio je priprema materijala velike poroznosti i fotokatalitičke aktivnosti imobilizacijom nanočestica TiO2 na aerogelove poli(mlečne kiseline) (PLA). PLA aerogelovi su pripremljeni u tri koraka: (1) rastvaranje polimera u hloroformu na 22 °C, (2) zamena hloroforma etanolom i (3) natkritično sušenje upotrebom CO2 na pritisku 19 MPa i temperaturi 39 ºC. Imobilizacija TiO2 nanočestica izvedena je in situ i ex situ metodama. Dobijeni uzorci su okarakterisani pomoću SEM, EDX i FTIR analize. Fotokatalitička aktivnost razvijenog materijala ispitana je prateći obezbojavanje vodenog rastvora boje C.I. Acid Orange 7. Pokazano je da imobilizacija TiO2 nanočestica ne utiče značajno na morfologiju PLA aerogelova. PLA aerogelovi sa TiO2 nanočesticama imobilisanim ex situ metodom održavali su plutabilnost tokom isitivanja i omogućili su potpuno obezbojenje rastvora boje nakon 330 minuta osvetljenja. Velika fotokatalitička aktivnost uzorka očuvana je tokom tri ponovljena ciklusa obezbojavanja rastvora boje.

Cellulose acetate films were impregnated with carvacrol using supercritical carbon dioxide. The supercritical impregnation process, conducted in a static regime at pressure of 21 MPa and temperature of 50°C, was optimized by variation in the processing time (30 and 120 min) and decompression rate (from 0.3 MPa/min to 36 MPa/min). Characterization of the obtained cellulose acetate films was performed by Atomic Force Microscopy and Differential Scanning Calorimetry. Effects of glycerol and carvacrol on the properties of the films were discussed. Release kinetics from the cellulose acetate film with 31.4% of carvacrol was investigated in a physiological saline solution. In addition, the Higuchi and Korsmeyer-Peppas release models fitted the carvacrol release curve well. Obtained cellulose acetate films impregnated with carvacrol can be of interest for the application in medicine as wound dressings considering their biocompatibility and biodegradability as well as their potential antimicrobial activity or in the food industry as an active food packaging., Filmovi acetata celuloze su impregnirani karvakrolom pomoću natkritičnog ugljenik(IV)-oksida. Proces natkritične impregnacije, izveden u statičkom režimu na pritisku 21 MPa i temperaturi 50°C, je optimizovan varijacijom procesnog vremena (30 i 120 min) i brzine dekompresije (od 0,3 MPa/min do 36 MPa/min). Karakterizacija dobijenih filmova acetata celuloze je izvedena pomoću mikroskopije atomskih sila i diferencijalne skenirajuće kalorimetrije. Efekat glicerola i karvakrola na karakteristike dobijenih filmova je objašnjen. Otpuštanje karvakrola iz filma koji je ima 31,4% primos impregnacije karvakrola je ispitano u fiziološkom rastvoru. Dodatno, Higuči i Korsmejer-Pepas modeli otpuštanja su dobro fitovali krivu otpuštanja karvakrola. Dobijeni filmovi acetata celuloze impregnirani karvakrolom mogu biti značajni za primenu u medicini za previjanje rana uzimajući u obzir njihovu biokompatibilnost i biodegradabilnost kao i potencijalno antimikrobno dejstvo ili u industriji hrane kao aktivno pakovanje.

The present work was aimed to study swelling kinetics of polylactic acid (PLA) and its impregnation with thymol in supercritical carbon dioxide (scCO2) medium. The influences of temperature and soaking time on the swelling kinetics and impregnation yield of PLA cylindrical disc and film were investigated. Swelling experiments were performed in a high pressure view cell at 10 MPa and temperatures of 40°C, 60°C and 75°C for 2 to 24 h. On the basis of swelling kinetics, pressure of 10 MPa and temperature of 40°C were chosen for supercritical solvent impregnation (SSI) of the PLA samples during 2 to24 h. The highest swelling extent was observed for the PLA monolith after 24 h treatment with pure scCO2 (7.5%) and scCO2 with thymol (118.3%). It was shown that sufficiently high amount of thymol can be loaded into both PLA monolith and film using SSI after only 2 h (10.0% and 6.6%, respectively). Monolith and film of PLA impregnated with thymol could be suitable for active food packaging and sterile medical disposables., Prikazana studija je namenjena ispitivanju kinetike bubrenja polilaktida (PLA) i njegovoj impregnaciji timolom u natkritičnom ugljenik(IV)-oksidu (nkCO2). Praćen je uticaj temperature i operativnog vremena na kinetiku bubrenja i prinos impregnacije PLA cilindričnog diska i filma. Eksperimenti bubrenja su izvedeni u ćeliji za rad pod visokim pritiscima na 10 MPa and 40°C, 60°C i 75°C od 2 h do 24 h. Na osnovu kinetike bubrenja, natkritična impregnacija uzoraka PLA timolom je izvedena na pritisku od 10 MPa i temperaturi od 40°C tokom 2 do 24 h. Najveći stepen bubrenja je imao PLA disk na 10 MPa i 40°C nakon 24 h (7,5%) u sistemu sa čistim nkCO2 i u sistemu sa timolom (118,3%). Pokazano je da se dovoljno visok prinos impregnacije timola može postići nakon 2 h (10,0% za disk i 6,6% za film). PLA u formi diska i filma impregnirani timolom su pogodni materijali za aktivno pakovanje hrane i za sterilni medicinski pribor.

The impregnation of differently prepared chitosan gels with thymol using supercritical carbon dioxide (scCO2) was studied in order to obtain new materials with added value without the use of organic solvents. The optimum conditions of supercritical impregnation (15 MPa, 35 °C and 24 h) were defined based on previously investigated thymol solubility in scCO2. Cross-linkers formaldehyde and glutardialdehyde were used to prepare chitosan hydrogels. The obtained hydrogels of chitosan were converted in acetogels and then dried with air or by using scCO2 in order to obtain xerogels and aerogels. The best results, in terms of morphology and yield of impregnation with thymol, have been achieved for the aerogel of chitosan (11.30%) which was obtained with cross-linker formaldehyde and dried with scCO2 at 15 MPa and 50 °C., U radu je ispitivana impregnacija različito pripremljenih hitozan gelova sa timolom pomoću natkritičnog ugljenik(IV)-oksida (nkCO2) u cilju dobijanja novih materijala sa dodatom vrednošću bez upotrebe organskih rastvarača. Optimalni uslovi natkritične impregnacije (15 MPa, 35 °C i 24 h) su definisani na osnovu prethodno ispitane rastvorljivosti timola u nkCO2. Za pripremu hidrogelova hitozana korišćeni su umreživači formaldehid i glutardialdehid. Dobijeni hidrogelovi hitozana su prevedeni u acetogelove, a potom sušeni na vazduhu ili pomoću nkCO2 kako bi se dobili kserogelovi ili aerogelovi. Najbolji rezultati u pogledu morfologije i prinosa impregancije sa timolom postignuti su za aerogel hitozana (11,30%) koji je dobijen umrežavanjem sa formaldehidom i sušenjem sa nkCO2 na 15 MPa i 50 °C.