Prediction of Release Characteristics of Film‐Coated Urea from Structure Characterization Data of the Film

Abstract

An efficient method for the prediction of the release characteristics of film-coated urea from its film structure is proposed. A model spray-coating apparatus was built to prepare a plane film to directly measure the film permeability coefficients by simulating the characteristics of randomness, intermittence and multiple layers of the coating, and eliminating particle collision effects. From analysis, the spraycoated film structure can be modeled as comprising a dense structure and a defect structure. Both structures contributed to the penetration flux and the apparent permeability coefficients of the film for water and urea diffusion. The permeability coefficients of the plane films were calculated from the film structure model, and were shown to be close to the measured values.

Photodegradation of Polymer Materials Used for Film Coatings of Controlled‐Release Fertilizers

“…S1 in the Supporting Information [29]. A film with a diameter of 40 mm was fixed in the central connector of the U-shaped tubes.…”

Implementation of Biodegradable Liquid Marbles as a Novel Controlled Release Fertilizer

“…The presence of micro-scale defects in thinner polymeric shells will thus have a much larger effect on the release of nutrients relative to those found in thicker coatings, i.e., there is an inverse relationship between the coating thickness and the effective diffusivity through the material itself. , This likely explains the increased diffusivities observed for the thinner polymer shells investigated in this work. It is understood that a “threshold thickness” can eventually be realized where the material essentially becomes “defect-free” and a constant diffusivity is obtained . Unfortunately, this could not be confirmed in this work due to not having polymer particles of greater size to create thicker polymeric shells.…”

“…It is understood that a "threshold thickness" can eventually be realized where the material essentially becomes "defect-free" and a constant diffusivity is obtained. 31 Unfortunately, this could not be confirmed in this work due to not having polymer particles of greater size to create thicker polymeric shells. More detailed modeling works on the effects of defects in fertilizer coatings can be found elsewhere in the literature.…”

“…It is interesting to note that the calculated diffusion coefficient for the urea/PCL shell was found to change linearly with variations in shell thickness, as detailed in Table . As diffusion coefficients are principally an intrinsic and unchanging value of a specified polymeric material (i.e., thickness independent), this was not an anticipated result; however, it is regularly observed in the literature when polymeric materials are used as fertilizer coatings. ,,− …”

“…Unfortunately, this could not be confirmed in this work due to not having polymer particles of greater size to create thicker polymeric shells. More detailed modeling works on the effects of defects in fertilizer coatings can be found elsewhere in the literature. , …”