Effect of citric acid on porcine plasma protein bioplastics processed through injection moulding

The replacement of petrochemicals by biopolymers in the production of plastics has some limitations, such as the poorer mechanical properties of the latter. Thus, when using porcine plasma protein (PPP) as raw material for developing bioplastics, the use of strengthening agents is required. Common additives currently used for that purpose, such as glutaraldehyde, negatively impact the biodegradability and toxicity of those materials. This study evaluates the effect of a green crosslinker like citric acid (CA) on PPP-based bioplastics. Therefore, using glycerol (gly) as a plasticizer, CA was added to the blend at different contents (0, 2.5, 5, 10%), either keeping the PPP/gly or (PPP + CA)/gly ratios at 1/1. Then, blends were injection moulded into biodegradable plastics, for which both mechanical properties and thermal stability improved as CA content was higher, as water absorption was hindered. However, it increased as CA content got higher, due to the acidification of the immersion media, but being always lower than the system without crosslinker. These findings suggest that citric acid, a natural, non-toxic, and abundant substance, could replace synthetic crosslinking agents in the development of PPP-based bioplastics.