C. Peña

Enhancing water repellence and mechanical properties of gelatin films by tannin addition

In order to reduce pollution caused by traditional non-biodegradable plastic films, renewable raw materials from plants and wastes of meat industries have been employed in this work. A hydrolysable chestnut-tree tannin was used for gelatin modification. Films of gelatin and gelatin-tannin were obtained by casting at room conditions. Transition temperatures of both gelatin and gelatin-tannin systems were determined by differential scanning calorimetry (DSC). Glass transition temperatures of modified gelatin occurred at higher temperatures than for neat gelatin. Enthalpy and temperature of helix-coil transition decreased when tannin content increased due to variations in the helical structure of gelatin as a consequence of tannin presence in agreement with X-ray analysis. Mechanical and thermal behaviour varied as a function of the content of tannin, showing optimum values for films modified with 10 wt% tannin. The transparency of films was maintained after modification with tannin. Solubility and swelling tests of the films revealed that the presence of tannin reduced the water affinity of gelatin.

Diels-Alder "click" chemistry for the cross-linking of furfuryl-gelatin-polyetheramine hydrogels†

This paper deals with the design of biopolymeric hydrogels after the chemical cross-linking of gelatin through the Diels–Alder (DA) reaction. Furan modified gelatin (Gel-FGE) was prepared by the reaction of furfuryl glycidyl ether with the free amino groups present in the gelatin. A Jeffamine®-based bismaleimide was employed as a cross-linking agent and the influence of the amount of cross-linker used on the final hydrogel properties was studied. The DA and retro-DA reactions were followed by ultraviolet spectroscopy and the final properties of the hydrogel assessed. Scanning Electron Microscopy was used to analyze the structure of the final material and rheology studies confirmed the formation of a chemically cross-linked network. The swelling behavior in response to external stimuli such as pH and salt concentration was also studied. By virtue of the DA “click” reaction, biopolymer-based cross-linked hydrogels, with promising properties for biomedical applications, were obtained in a simple one step procedure free of catalysts, additives or coupling agents.

Bionanocomposites based on thermoplastic starch and cellulose nanofibers

The goals of this work are to obtain thermoplastic starch (TPS) with different glycerol/water ratios, verify its characterization by different techniques, and study the influence of addition of cellulose nanofibers in the matrix of TPS. The general procedure for processing starchy materials involves granular alteration with the combination of temperature, shear, and plasticizers. Distilled water and glycerol are used as plasticizers, and the influence of both of them has been studied in tensile properties. By infrared spectroscopy analysis, the addition of plasticizers created new physical links (hydrogen bonds) with starch molecules thereby shifting the characteristic peaks of native corn starch to higher wave number. The most suitable composition for the elaboration of bionanocomposites has been determined and bionanocomposites with different content of cellulose nanofibers have been obtained and their mechanical properties have been studied.