An Investigation in Poly (Lactic Acid)‐Cellulose Acetate Composites Used for the Controlled Release of Potassium Fertilizers

Abstract

Biodegradable polymer–based controlled‐release fertilizers (CRFs) offer an environmentally friendly approach to enhancing nutrient use efficiency while minimizing ecological impacts. In this study, poly (lactic acid) (PLA), cellulose acetate (CA), and their blends were investigated as carrier matrices for potassium (K + ). Composites containing 10 wt% potassium sulfate (KS) were produced by melt compounding, followed by comprehensive characterization of their physical, thermal, rheological, mechanical, and K + release performances. The density results confirmed uniform dispersion of KS throughout all formulations. Melt flow index and rheological behaviors revealed that CA content governed melt fluidity, while KS slightly reduced viscosity without compromising processability. Differential scanning calorimetry showed that increasing CA content suppressed PLA crystallinity (from 4% to 2.9% for the blends with no KS loaded and from 5.4% to 3.7% for KS blends) and promoted predominantly amorphous structures, with CA further modulating chain mobility depending on the material composition. The tensile behaviors indicated that PLA contributed strength and stiffness, while CA enhanced ductility; however, limited interfacial compatibility resulted in non‐linear responses, and KS incorporation caused a moderate decline in tensile strength (~17.4%). The K + release studies demonstrated strong dependence on both polymer composition and release environment, where PLA40‐CA60/10% KS exhibited enhanced and tunable K + release, while soil condition produced slower and more complicated release profiles ( n values > 0.5) compared with water condition ( n values < 0.5). Overall, these findings demonstrate that PLA–CA composites effectively mitigate nutrient losses from leaching and percolation, while offering excellent processability and environmental sustainability.