Biodegradable Hydrophilic Film of Crosslinked PVA/Silk Sericin for Seed Coating: The Effect of Crosslinker Loading and Polymer Concentration

Abstract

Biodegradable polymers are already used in many industries due to their environmental benefits, however their use in agriculture is not yet widespread. Herein, a new biodegradable film of crosslinked poly(vinyl alcohol) (PVA)/silk sericin (SS) was explored and used to coat seeds in order to protect seeds from environmental risk factors with the aim to enhance germination. Films of PVA/SS with different loadings of dimethylurea (DMU, crosslinker) and with different concentrations of PVA were fabricated using an organic solvent free casting process. These crosslinked films were characterized for their thickness, morphology, functional groups, mechanical properties, hydrophilicity and swelling. The results found that the crosslinked film composed of 20% w/w DMU, 10% w/v PVA and 2% w/v SS had good mechanical and physical properties due to higher DMU contents promoting greater crosslinking via hydrogen bonding. This film composition was used to coat on lablab bean seeds by a spray rotary coating machine. Coated and non-coated seeds were compared for their imbibition, water vapor uptake and germination. The coated seeds showed higher imbibition and water vapor uptake than non-coated seeds due to the hydrophilic properties of PVA and SS, which helps to promote higher % germination of the coated seeds. This new biodegradable hydrophilic film of crosslinked PVA/SS has potential for use in seed coating technology.