Miscibility and morphology of kefiran/waterborne polyurethane blend films

Abstract

Biodegradable blends of kefiran with various contents (10-40 wt%) of waterborne polyurethane were successfully synthesized via the casting method. When waterborne polyurethane content is lower than 30 wt%, good compatibility and miscibility were observed; otherwise, phase separation occurs between them. These phenomena can be attributed to intermolecular interactions, which were confirmed by Fourier transform infrared, X-ray diffraction, differential scanning calorimetry analysis, and scanning electron microscopy. Compared with kefiran film, the blends increased in thickness, tensile strength, elongation at break, yellowness, and opacity when the waterborne polyurethane content was increased. Meanwhile, the water vapor permeability and moisture absorption significantly decreased (p < 0.05).

The Effect of Extraction Conditions on the Barrier and Mechanical Properties of Kefiran Films

“…2900 cm −1 corresponds to C-H stretching vibration, and in this zone a decrease is also evident [49]. The increase in glycerol concentration leads to higher numbers of O-H bonds and consequently higher band areas, also resulting in a decrease in the areas that correspond to the C-H bonds [34,50]. The next region, 3000-2800 cm −1 , is representative of the bands attributed to the symmetric and anti-symmetric stretching modes of C-H in the methyl (CH 3 ) and methylene (CH 2 ) functional groups [35].…”

“…The kefiran film denoted as F_80.30 (Figure 2B) has a smooth structure, is homogeneous and free of air bubbles, and represents a continuous matrix without any cracks and with good integrity. In the study conducted by Rad et al, 2018, the samples of waterborne polyurethane and pure kefiran films showed uniform morphology without pores or cracks [34]. The rest of the samples have a porous structure.…”

“…The mixture was then cooled and centrifuged at 10,000 g for 10 min. The polysaccharide dissolved in the supernatant was purified with an equal amount of chilled ethanol [34] by freezing at −20 • C overnight, followed by a slow thawing, avoiding the destruction of the polysaccharide structure. After centrifugation at 5000 g for 10 min at 4 • C, the kefiranrich pellets were dissolved in distilled water at 60 • C. The precipitation procedure was repeated twice.…”

“…Owing to the hydrophilicity of kefiran, the WVP values registered a gradual increase during the testing period. To prevent this drawback, Rad et al (2017) [34] proposed an improvement in the protection against water vapor by adding a polymeric carbohydrate, such as starch.…”

Biotechnological challenges and perspectives of using exopolysaccharides

“…27 Research has shown applicability of this EPS in the food industry: a) increase in the viscosity of aqueous solutions and acid milk gels; 17 b) production of edible and transparent EPS similar to most films based on polysaccharides, applicable to regulate transferring of gas, aroma, flavour and oils in a food system; c) increase in the shelf-life and quality of food products, among others. 28 Levan is a natural (Bacillus subtilis and other microorganisms) Homo-EPS composed of fructose monomers. It has many different properties, such as high solubility in oil and water, adhesiveness, good biocompatibility and film forming capacity, great potential as a new functional biopolymer in food, animal food, cosmetic, pharmaceutical and chemical industries.…”