Encapsulation of acidified chitosan within partially cross-linked natural rubber matrices and their potential slow-relea
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ORIGINAL PAPER
Encapsulation of acidified chitosan within partially cross‑linked natural rubber matrices and their potential slow‑release application Muhammad Rahim1 · Mas Rosemal Hakim Mas Haris1 · Norhidayah Abu1 Received: 28 February 2020 / Accepted: 2 September 2020 © The Malaysian Rubber Board 2020
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. Keywords Biocomposite · Chitosan · Encapsulation · Naphthols · Natural rubber · Slow release
Introduction Pesticides have been used increasingly over the past 60 years to improve both yield and quality of agricultural production [1]. The widespread use of pesticides is a major problem, with about three million metric tons of pesticides applied annually [2]. Pesticides are toxic compounds that can cause serious environmental and human health problems. They have been widely recognized as a contaminant in the natural environment due to high concentration which can kill or adversely affect natural communities [3]. Freshwater contamination due to leaching of pesticides is a critical environmental issue that has appeared within the past few decades, while runoff is considered the main source of surface water contamination [4]. Pesticide exposure can cause cancer, damage to the immune system, kidney problems and adverse reproductive effects in humans [5]. * Muhammad Rahim [email protected] 1
School of Chemical Sciences, Universiti Sains Malaysia, 11800 Pulau Penang, Malaysia
Increased attention has been focused recently on developing a slow-release formulation which can produce the active chemical compounds over a long period. The use of a slow-release formulation can minimize
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