INVESTIGADORES
MARTUCCI josefa Fabiana
congresos y reuniones científicas
Título:
Relationship between crosslinking degree and fracture toughness of gelatin gels.
Autor/es:
M. CZERNER; J. F. MARTUCCI; L.A. FASCE; R.A. RUSECKAITE; P.M. FRONTINI
Reunión:
Congreso; 14 Congreso Internacional en Ciencia y Tecnología de Metalurgia y Materiales SAM ? CONAMET.; 2014
Resumen:
Gelatin is a biopolymer with the ability to form thermoreversible physical gels. Gelatin based gels are well-known for their several uses in photography, ballistic, food and pharmaceutical industries as well as novel applications in the biomedical field. When cooling, gelatin solutions undergo a conformational transition from coil to helix and a tridimensional physical network is progressively formed. Then, the gel is constituted by ordered triple helical collagen-like sequences (physical crosslinking points) interconnected by flexible protein chains. The amount of triple helices developed depends on several parameters such as protein source (indeed chemical composition), molecular weight, gelatin concentration, modifications of the environment (pH, salts, solvents, etc) and thermal history, between others. However, it has been established that the storage modulus of gelatin gels is determined by the sole helix concentration, leading to a master curve valid for different samples investigated. Inspired by this study, the aim of this work is to explore if fracture toughness of gelatin gels is also governed by helix concentration. For this, several gel samples differing in gelatin concentration, source (bovine or porcine), solvent (water or water-glycerol, water-sorbitol mixtures) and crosslinking type (physical or chemical induced by glutaraldehyde) were studied. Fracture toughness (Gc) is determined by the wire cutting method and the helix concentration is estimated trough the crosslinking degree. Samples were characterized by the number-average molecular weight between two crosslinking points, determined by using the Flory?Renher equation. The ultra-structures of the gels were analyzed by SEM. Increasing gelatin concentration leads to higher Gc values and porcine gelatin gels series exhibit higher fracture toughness than bovine gelatin gels ones. These results are consistent with a more crosslinked structure. The addition of glycerol and sorbitol in gel formulations appears to promote a large number of bridging sites in the gel main network and is reflected in higher Gc values. The results obtained in our experiments identify the relevance of triple helix concentration as key parameter determining fracture toughness values of gelatin gels.