Biodegradable mulch films obtained from unique combinations of cellulose, polycaprolactone, keratin and calcium carbonate

Abstract

Biodegradable mulch films from cellulose (CELL), cellulose/polycaprolactone (CELL/PCL), cellulose/polycaprolactone/keratin (CELL/PCL/KER) and cellulose/polycaprolactone/keratin/ground calcium carbonate (CELL/PCL/KER/GCC) were prepared using Ionic liquid as a green solvent. Pure cellulose biopolymer is characterised by better mechanical properties (tensile strength - force per unit cross-sectional area at breakage - of 75.3 MPa and modulus of elasticity of 944.4 MPa) than the other studied samples which is attributed to the formation of partially miscible polymer blends. Among samples containing PCL, CELL/PCL/KER/GCC has the highest tensile strength and modulus of elasticity. The addition of KER or KER/GCC to CELL/PCL films resulted in an increment in melting temperature and an improvement of sample crystallinity. The light transmittance of all films was >60 %. The incorporation of KER enhanced the biodegradability of the biocomposites, while KER/GCC addition slightly inhibited degradation due to an increased hydrophobicity and crystallisation growth of semi-crystalline biopolymers. The reported method for mulch film preparation is green and recyclable, and, when including a readily available source of KER, such as by extraction from waste chicken feathers, enables conversion to organic biofertiliser. The findings of this study contributed to sustainable agriculture by providing nutrients that enhance the growth speed of the plant, and hence food production, and reduce environmental pressure. Inclusion of GCC additionally provides not only Ca2+ for plant consumption but also soil pH control.