Investigation of deep eutectic solutions as plasticizers in polymer blend films

Deep eutectic solutions (DES), one of the green solutions, are mixtures of two components that can bond with each other to form an eutectic mixture and have a final melting point lower than the melting point, and have properties that respond to the expectations of green chemistry. Deep eutectic solutions are emerging as a new generation of solvents with great potential for a variety of applications. In recent years, they have received considerable attention as promising alternatives to flammable organic solutions. Plasticizers with toxic effects such as phthalate and adipate are used extensively in the main petroleum-derived synthetic plastics such as polyethylene, polypropylene, polyvinyl chloride and polyethylene terephthalate, which are used as flexible food packaging. Problems with the impact of low molecular weight plasticizers on humans and the environment have put pressure on the industry to expand the application of other groups of plasticizers and to seek innovative alternatives. It is important to use deep eutectic solutions, which do not have toxic effects but have similar technical properties, instead of these substances, which have many negative effects on human and environmental health. In this study, the usage possibilities of the addition of DES as a plasticizer to the mixed polymer granules, which are used as flexible food packaging, were investigated. By using four different hydrogen bond donors (lactic acid, hexanoic acid, pantoneic acid and urea) with hydrophilic and hydrophobic character and choline chloride as the hydrogen bond acceptor, mixtures of DES were prepared in 1:1 and 1:2 molar ratios and 5-10-20% concentrations, It was added to the granules in a twin screw extruder and flexible films were obtained. The characterization analyzes of the DES were made and the mechanical, barrier and water behavior properties of the sections taken from the films as well as the possibilities of use were examined by applying FTIR and DSC analyzes. Compliance of the films with legal obligations was evaluated by total migration analysis. Multi-Criteria Decision Making (TOPSIS) method was used to determine the most suitable films among 28 different films produced according to the trial design. Viscosities of DES's were found to be 18.7-202.9 mPa.s, densities of 0.95-1.18 g/ml, pH values of 0.05-8.9 and volatility between 0.8-18.9%. The thickness values of the films produced with or without DES additives are 0.12-0.22 mm, breaking force 12.18-19.22 MPa, elongation at break 281.3-656.5%, bursting force 13.19-25.86 N , burst elongation 3.51-5.76 mm, water vapor permeability 0.001-1.9 g/m².h, humidity 0.00-1.88%, water holding capacity 1.02%-4.22%, water solubility 0.00-1.86%, heat seal 1.69-6.52 N, total migration LOD-27 mg/dm². In terms of mechanical properties, improvements in breaking force, elongation at break, bursting force and burst elongation were observed. Statistically expected results were also obtained for barrier properties. The fact that migration analyzes are within the legal limits also shows that DES's are reliable additives. As a result, it has been observed that deep eutectic solutions provide improvements in the properties of the polymer, as predicted.