HPMC Layered Tablets Modified with Chitosan and Xanthan as Matrices for Controlled-Release Fertilizers

MARIANA A. MELAJ; MARTA E. DARAIO

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2014 vol. 131 p. 1 - 7

0021-8995

Polymeric matrices based on hydroxypropyl methylcellulose (HPMC) with xanthan (X) or chitosan (Q) and using KNO3as a model fertilizer were prepared as three-layered tablets and assayed as controlled release fertilizers (CRFs). The dynamic swellingbehavior was analyzed in order to interpret the water uptake mechanism, which in general proved to be non-Fickian. The presence ofHPMC allows a substantially constant rate of fertilizer release. The release mechanism of KNO3 was analyzed and can be described asnon-Fickian diffusion, with release exponents ranging from 0.85 to 1.01, suggesting polymer relaxation as the major process controllingfertilizer release. Durability in soil indicates the blend Q-HPMC as the more long-lasting matrix of those tested, remaining atleast 34 weeks. Both blends improve HPMC properties for agronomical applications, with X-HPMC increasing the swelling rate andQ-HPMC extending the permanence in the soil. Therefore, layered X-HPMC and Q-HPMC matrices can be proposed as suitablematerials for the development of CRFs