Green Composite Based on PHB and Montmorillonite for KNO₃ and NPK Delivery System

Controlled release fertilizer (CRF) as a safe system for reducing environmental pollution still remains as demand for the agribusiness. Natural and biodegradable polymer materials have been proposed as a prominent and sustainable controlled delivery system. Composite based on polyhydroxybutyrate (PHB), starch, glycerol and montmorillonite (PHBSGMMt) has been proposed as a carrier for controlled release fertilizers, such as KNO₃ and NPK. PHBSGMMt with 10 wt% of KNO₃ or NPK processed by melting at 162 °C, 60 rpm during 10 min in a mixer chamber of torque rheometer. Composites were characterized according to its structure by FTIR and XRD, in thermal behavior by TGA and DSC, and morphology by SEM. Fertilizers release in water was determined by ionic conductivity. Clay, KNO₃, and NPK increased the PHB/starch compatibility and homogeneity, resulting in a well-interfaced material obtained for PHBSGMMTNPK. MMtKNO₃ was mainly on PHB phase and MMtNPK on the compatible polymeric phase. These behaviors explain the faster release of KNO₃ in water medium since the KNO₃ has high solubility and the phase separation creates fissures that turn in water pathway. Kinetic parameters classified the material as a non-Fickian diffusion or anomalous transport mechanism.