ABSTRACTDEVELOPMENT OF A POLY(LACTIC ACID) PACKAGING MATERIAL ABLE TO SCAVENGE CARBON DIOXIDE AND ETHYLENE BY INCORPORATION OF ZEOLITESByAnna Szwedzińska Poly(lactic acid) is a biobased polymer and known to biodegrade reasonably quickly in commercial compost. There has been a growing interest in using it as a replacement for petrochemical based polymers due to its environmental-friendliness. Zeolites are crystalline hydrated aluminosilicates of alkali and alkaline earth elements. They can be natural minerals or produced synthetically. Depending on their framework they can have different structures and different pore sizes which makes them sorption-specific systems for various volatiles. There is a growing interest in their application in food packaging as they can adsorb and absorb gases crucial for extending shelf life of fresh produce, like ethylene and CO2. Active packaging systems are efficiently used in food packaging. Studies show that PLA and zeolites can be combined into one material by extrusion. Now the question is if they can act as an efficient active packaging system. Results obtained showed that two chosen zeolites, natural clinoptilolite and synthetic type 4A, have high sorption capacities for ethylene and carbon dioxide. Experimental conditions were varied, temperatures of 230C and 70C, relative humidities of 0% and 100%, headspace gases composed of varying combinations and concentrations of ethylene, carbon dioxide, nitrogen, and oxygen. Although low temperature and the presence of water in the system decreased sorption capacities of the zeolites, most measured amounts of adsorbed ethylene and carbon dioxide were relevant to concentrations produced and higher than concentrations tolerated by fresh produce, and were promising enough to continue investigating these two zeolites when incorporated into/onto PLA films. Two techniques to produce PLA/zeolite films were tested, extrusion (followed by injection molding and compression)and bar solution coating. The second method resulted in films with higher sorption potential for the two investigated gases since extrusion resulted in the zeolites being too deeply incorporated into the polymer matrix and having PLA as the polymer with good barrier properties towards ethylene did limit their sorption capacities. Further development of the most efficient coating solution and coating method resulted in production of two zeolite coated PLA films. The newly developed films were compared in sorption studies to two commercially available bags that are claimed to be ethylene scavengers and as a result to extend fresh produce shelf life. PLA films proved to be comparable to one of the commercial bags comprised of LDPE impregnated with zeolites. The second commercial product did not show significant sorption of either of the two gases of interest. All film samples were tested in two conditions (230C, 0% RH and 70C and 100% RH).Although in both cases sorption of ethylene and carbon dioxide was smaller than for powder zeolites, with even higher decrease in low temperature and in the presence of water, the resulting sorbed amounts were still relevant to real life situations. Experiments designed to determine whether those films could be reused showed that both zeolite coated PLA films could be successfully reused in room temperature, the same as for the commercial film.
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