Effect of Salt Addition in Porcine Plasma Protein-based Bioplastics as a Strategy To Obtain Superabsorbent Materials

In recent years, there has been a growing interest in high-porosity materials, such as polyurethane foams, used alone or in combination with other polymers, for applications in various fields, including hygienic-sanitary, biomedical, agricultural, and food packaging. To replace non-biodegradable plastic materials with new-generation bioplastics that meet consumer expectations in terms of both performance and eco-sustainability, this work developed and tested porous composite materials based on porcine plasma protein (PPP), a biowaste from the meat industry. The bioplastics were obtained by blending PPP with a plasticizer (i.e., glycerol), keeping a PPP/glycerol ratio equal to 1, and then injection moulding was employed using two different mould temperatures (60 and 120 °C). In particular, the impact of using three different salts (i.e., ammonium bicarbonate, sodium bicarbonate, and sodium carbonate) at 5 w/w% content on the absorption performances of the bioplastics was evaluated. Chemical-physical characterizations, mechanical and rheological analyses, as well as liquid absorption tests (in different media and/or conditions) on all the obtained bioplastics were carried out. The bioplastic including sodium carbonate moulded at 60 °C gave the best material in terms of water uptake values at 24 h (3000 ± 200%), reaching similar values to those of a commercially available foam employed in female hygienic napkins (2800 ± 100%). Water uptake values ranging from 400 to 2250% were obtained for the rest of the PPP-based systems. In saline solution, tests carried out following the official protocols supplied encouraging results (i.e., FSC = 10.6 ± 0.4 g/g, CRC = 2.8 ± 0.7 g/g, AUL = 3.0 ± 0.1 g/g, and rewet = 0.86 ± 0.06 g), although there is still a gap between commercially available products and proposed bioplastics in terms of CRC and AUL. SEM evaluation confirmed this similarity as this system displayed a complex microstructure, characterized by a porous and interconnected structure. Therefore, the obtained results represent a significant step towards creating eco-friendly superabsorbent materials that meet industrial requirements.