Development of controlled release fertilizer systems for KCl using glycerol-based polymers

Abstract

Controlled release systems were developed using biodegradable polymers/copolymers via polycondensation of glycerol with acids (citric, adipic, and succinic) with potassium chloride (KCl) 0, 10, 20, and 40 wt% followed by crosslinking at 120°C. Polymers were characterized by thermogravimetry, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and UV-Vis spectroscopy. All are thermally stable up to 200°C, therefore suitable for release in countries where temperatures reach 50°C. Fractographic analysis showed rubbery (rough and ductile) and hard (smooth and brittle) polymers depending on the acid used. The release profiles showed that hydrophilic (polar) polymers are easily hydrolyzed, generating faster release reaching 52% in 120 h. Less polar polymers delay KCl release below 20% at the same time. Therefore, it was possible to adjust the release by controlling the fertilizer content and the type of polymer, designing a fast or slow release to meet the needs of a given crop.