Thermoplastic Blends Based on Poly(Butylene Succinate-co-Adipate) and Different Collagen Hydrolysates from Tanning Industry: I--Processing and Thermo-mechanical Properties

In this study, blends of a biodegradable thermoplastic polyester, poly (butylene succinate-co-adipate) (PBSA) with twodifferent raw hydrolyzed collagens (HCs), derived from the tannery industry, were investigated in terms of processability,rheological, thermal and mechanical properties. HCs, obtained by alkaline (HCa) and enzymatic (HCe) hydrolysis of the solidwastes generated during the shaving of the tanned leather, were used in PBSA/HC blends, up to 20 wt% of HC, produced bymelting extrusion and processed by injection molding. All the blends up to 20 wt% HCs resulted suitable for the injectionmolding obtaining flexible molded specimens with good tensile properties. The different secondary structure of the two HCsinfluenced the rheology, morphology and mechanical properties of the produced blends. In particular, HCa, due its highercontent of oligopeptides and free amino-acids, showed a good compatibility with the polymeric matrix acting as a plasticizerwith consequent reduction of melt viscosity with increasing its loading. The molded dog-bones specimens containing 20wt% HCa showed a value of elongation at break of 810%. While, HCe, due its higher presence of b-sheet structures, behavedas organic filler, showing a poor interfacial interaction with PBSA with consequent decrease of the tensile properties withincreasing its loading. The good processability and satisfactory mechanical properties obtained encourage the use of bothinvestigated collagen hydrolysates in the production of thermoplastic blends and relative molded products for applicationsin agriculture and plant nurseries, such as pots or small containers with fertilizing properties, due the presence of HCs.