Encapsulation of acidified chitosan within partially cross-linked natural rubber matrices and their potential slow-release application

Abstract

Biocomposites comprising acidified chitosan (CTS) encapsulated in partially cross-linked natural rubber (NR) matrices (CTS-e-NR) were prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FE-SEM). The results of FT-IR, TGA and FE-SEM revealed that CTS was merely encapsulated within partially cross-linked natural rubber, and no chemical interaction was observed between CTS and NR. Soil burial biodegradation studies indicated that CTS-e-NR was degraded beyond any doubt, and weight loss of 48.98% was observed within 8 months. The release behaviour of CTS-e-NR was investigated in distilled water, where the naphthols (pesticide precursors) 1-hydroxynaphthalene (1-N), 2-hydroxynaphthalene (2-N), 1,4-dihydroxynaphthalene (1,4-N) and 2,6-dihydroxynaphthalene (2,6-N) were used as model pesticides. The percentage released in the first 24 h was found to be 7.38, 4.39, 2.96 and 6.95%, while 62.69, 60.64, 22.68 and 40.985% was released at the 35th day, for 1-N, 2-N, 1,4-N and 2,6-N, respectively. The release of naphthols followed non-Fickian diffusion: the combination of both polymer erosion and diffusion release mechanisms. In addition, the release behaviour was found to be consistently controlled and prolonged over a period of 35 days. Therefore, CTS-e-NR is strongly recommended for the controlled-release application of real pesticides.