Optimization of ethyl cellulose-coated urea for high-performance controlled release

The development of controlled-release urea (CRU) using ethyl cellulose (EC) represents a significant strategy for advancing the green and sustainable development of agriculture. However, limited research on EC-coated urea preparation was reported before. This study employed EC/ethanol to develop CRU through fluidized bed technology and investigated the effects of the coating processes, material plasticization modification and surface treatment on the film structure and nitrogen release properties of CRU. The results demonstrated that the fluidizing gas temperature significantly influenced both the film structure and release performance. When the coating temperature was 50 °C, a continuous and uniform dense film was formed, resulting in optimal controlled-release performance lasting up to 7 days. Additionally, the effects of the peristaltic pump rate and coating liquid concentration were minimal. The plasticization effect of DBS was validated through XRD analysis, which demonstrated a reduction in the crystallinity of the EC, an enhanced fracture elongation of the film, and an extended controlled-release performance to 10 days. Furthermore, surface treatment with 1 % and 2 % paraffin wax improved the water barrier properties of the film, increasing its water contact angle from 100° to 130°. Consequently, the controlled-release period of the coated urea was extended to 50 days, meeting the ISO 18644:2016 standard. This study is valuable for fertilizer production and provides a reference for cellulose-coated fertilizers.