Polilaktid kao komponenta ekološki prihvatljivih kompozitnih materijala

The biodegradable linear aliphatic thermoplastic polyester poly(L-lactide) (PLA) is producible from agricultural products, such as corn. This polymer has been widely used as a biocompatible material for applications in surgical suture, medical implants and controlled drug delivery. Owing to its good mechanical properties and versatile fabrication processes the PLA has tremendous potential in traditional applications such as food packages, industrial devices, fibers, and green composites The goal of this work was to modify the mechanical properties of composite materials based on different PLA types and silica nanoparticles using thermoplastic elastomer.Biodegradabli linearni alifatični termoplastični poliestar poli(L-laktid) (PLA) se dobija iz poljoprivrednih proizvoda kao što su kukuruz ili šećerna repa. Ovaj polimer se intenzivno upotrebljava kao biokompatibilni materijal za primene kao što su hirurški konci, medicinski implantati i sistemi za kontrolisano otpuštanje lekova. Zahvaljujući dobrim mehanickim svojstvima i mogućnostima različitih postupaka prerade, PLA ima ogroman potencijal u tradicionalnim primenama kao sto su ambalaža za hranu, industrijska oprema, vlakna i zeleni kompoziti. Cilj ovog rada je bio da se primenom termoplastičnog elastomera modifikuju mehanička svojstva kompozitnih materijala na osnovu različitih tipova PLA (za ekstruziju, za duvane filmove, za biaksijalno orijentisane filmove) i nano čestica silicijum dioksida

Dobijanje razgranatih kopoliestara od ricinusovog ulja kao inicijatora

Using renewable feedstocks, such as biomass, for the production of polymers can have both environmental and economic benefits. The goal of this project was to synthesize the renewable copolymers from monomer l-lactide and castor oil as an initiator. In sample formulation the mass ratio of the monomer to the initiator was in the range from 4,53 to 21,5. The ring-opening polymerization was carried in a microwave reactor using tin(II)2- ethylhexanoate as a catalyst. The molar masses of obtained star-shaped polymers were assessed using SEC method. The thermal properties of the branched polymer were evaluated using differential scanning calorimetry. The molecular mass of the branched polymer increased with increasing the feed ratio of lactide and castor oil.Korišćenje obnovljivih sirovina, kao što je biomasa, za proizvodnju polimera može da ima i ekološke i ekonomske prednosti. Cilj ovog rada je bila sinteza obnovljivih kopolimera na osnovu monomera L-laktida i ricinusovog ulja kao inicijatora. U sirovinskom sastavu uzoraka maseni odnos monomera L-laktida i inicijatora ricinusovog ulja bio je u opsegu od 4,53 do 21,5. Polimerizacija otvaranjem prstena je izvršena u mikrotalasnom reaktoru primenom kalaj(II)etilheksanoata kao katalizatora. Molske mase dobijenih zvezdastih polimera su određene pomoću SEC metode. Toplotna svojstva razgranatih polimera određena su metodom diferencijalne skenirajuće kalorimetrije. Molske mase razgranatog polimera rastu sa porastom masenog odnosa laktida i ricinusovog ulja

Razvoj postupaka polimerizacije L-laktida

To determine the appropriate conditions for the polymerization of (Llactide), to obtain poly(L-lactide) a few different methods were applied: in closed vials under vacuum, in the reactor under high pressure, in the microwave reactor and in a reactor with solvent using the initiator. The molecular masses of prepared samples were determined using GPC method. It was assessed that by microwave synthesis method for the polymerization time less than 30 minutes the resulting polymer have the highest molecular mass, 178.000 g mol-1. It was estimated that the samples synthesized with trifluoromethanesulfonic acid as initiator have the best thermal stability.Za određivanje optimalnih uslova za polimerizacije (L- laktida), za dobijanje poli (L-laktida) (PLLA) primenjene su različite metode polimerizacije: u zatvorenim posudama pod vakumom, u reaktoru pod visokim pritiskom, mikrotalasnom polju i u rastvoru sa inicijatorom. Za određivanje molekulskih masa korišćena je GPC metoda. Ustanovljeno je da je mikrotalasna sinteza postupak sa najkraćim vremenom polimerizacije (manjim od 30 minuta) pri čemu je nastaje polimer koji ima najveću molarnu masu 178.000 g mol-1. Najbolju termičku stabilnost imao je uzorak PLLA sintetisan sa trifluorometansulfonskom kiselinom kao inicijatorom

UTICAJ TEMPERATURE NA PIROLIZU OTPADNE PLASTIKE U REAKTORU SA FIKSNIM SLOJEM

Piroliza, kao jedna od tehnika hemijske reciklaže plastičnih materijala, danas izaziva sve veća intersovanja kao ekološki i ekonomski prihvaljiva opcija obrade otpadnih materijala. Istraživanja ovih procesa se provode pri različitim eksperimentalnim uslovima, u različitim vrstama reaktora i sa različitim sirovinama, što čini poređenje procesa i direktnu primjenu procesnih parametara dosta složenim. U ovom radu dati su rezultati istraživanja uticaja temperature, u intervalu od  450°C do 525°C, na prinos procesa pirolize smjese otpadne plastike u sastavu: polipropilen 40%, polietilen niske gustine 35% i polietilen visoke gustine 25%. Istraživanja su provedena u pilot reaktoru sa fiksnim slojem koji je razvijen za ovu namjenu. Rezultati provedenih istraživanja pokazuju da se pri temperaturi od 500°C  postiže potpuna konverzija sirovine u vremenu od 45 min, uz maksimalni prinos pirolitičkog ulja od 32,80%, prinos gasovitih produkata od 65,75% i čvrsti ostatak od 1,46%. Sa daljim porastom temperature raste prinos gasovitih produkata, na račun smanjenja prinosa pirolitičkog ulja. Dobijeno pirolitičko ulje ima visoku toplotnu moć (45,96 МЈ/kg), te u tom pogledu ima potencijal primjene kao alternativno gorivo

Ambient particulate matter source apportionment using receptor modelling in European and Central Asia urban areas

This work presents the results of a PM2.5 source apportionment study conducted in urban background sites from 16 European and Asian countries. For some Eastern Europe and Central Asia cities this was the first time that quantitative information on pollution source contributions to ambient particulate matter (PM) has been performed. More than 2200 filters were sampled and analyzed by X-Ray Fluorescence (XRF), Particle-Induced X-Ray Emission (PIXE), and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to measure the concentrations of chemical elements in fine particles. Samples were also analyzed for the contents of black carbon, elemental carbon, organic carbon, and water-soluble ions. The Positive Matrix Factorization receptor model (EPA PMF 5.0) was used to characterize similarities and heterogeneities in PM2.5 sources and respective contributions in the cities that the number of collected samples exceeded 75. At the end source apportionment was performed in 11 out of the 16 participating cities. Nine major sources were identified to have contributed to PM2.5: biomass burning, secondary sulfates, traffic, fuel oil combustion, industry, coal combustion, soil, salt and “other sources”. From the averages of sources contributions, considering 11 cities 16% of PM2.5 was attributed to biomass burning, 15% to secondary sulfates, 13% to traffic, 12% to soil, 8.0% to fuel oil combustion, 5.5% to coal combustion, 1.9% to salt, 0.8% to industry emissions, 5.1% to “other sources” and 23% to unaccounted mass. Characteristic seasonal patterns were identified for each PM2.5 source. Biomass burning in all cities, coal combustion in Krakow/POL, and oil combustion in Belgrade/SRB and Banja Luka/BIH increased in Winter due to the impact of domestic heating, whereas in most cities secondary sulfates reached higher levels in Summer as a consequence of the enhanced photochemical activity. During high pollution days the largest sources of fine particles were biomass burning, traffic and secondary sulfates.JRC.C.5-Air and Climat