Structurally stable polyvinyl alcohol/sodium alginate-based optimally designed electrospun mats as mechanistically robust controlled-urea-release-systems

The present study deals with the development of uniform, bead-free, and urea-loaded PVA/SA-based sustainable electrospun fibrous constructs as a controlled release fertilizer system. Taguchi L9 OA was used to predict the optimal level of control parameters i.e., urea loading (∼ 45 phr), flow rate (∼ 1 ml/h), polymeric concentration (∼ 8 wt%), and an applied voltage of ∼ 25 kV, to fabricate EMs with minimum fiber diameter (∼ 0.208 µm) and diametral variation (∼ 0.017 µm). Microstructural analysis confirmed the presence of hydrogen bonding interactions between urea and the polymer matrix, as well as successful ionic crosslinking. The contact angle and thermogravimetric analysis indicated an increase in hydrophobicity (from ∼ 30.64º to ∼ 74.13º) and thermal stability (from 164 ºC to ∼ 290 ºC) for PVA/SA-based EMs upon urea incorporation and post crosslinking, respectively. Further, the effect of urea loading and crosslinking on swelling and degradation behavior revealed a subsequent increase in water absorption capacity up to ∼ 296 % accompanied by a decrease in degradation rate up to ∼ 13%. The swelling behavior of EMs exhibited a desirably good level of pH level, salt/alkali solution sensitivity, and water retention potential lasting up to ∼16 days in soil. Spectroscopic analysis revealed a non-Fickian diffusion-induced sustained release of urea in water (> 21 days) and soil media (> 30 days). Soil burial studies of crosslinked urea-loaded EMs exhibited excellent biodegradability (> 80 % in 60 days) and structural stability (∼30 days). Thus, the study demonstrated the design of mechano-functionally engineered urea-loaded optimized PVA/SA-based EMs as potential controlled nutrient release substrates with improved and sustainable physicomechanical performance for agricultural practices.