Encapsulation of chlorothalonil with polylactic acid using nanoprecipitation method for rubberwood preservation

IRG/WP 18-30722

T-J Teng, M N M Arip, R Kadir, E-P Ng, H-L Lee

Wood is a very beneficial material for humankind. The current trend is employing organic biocides as wood preservatives to inhibit the wood from biodeterioration caused by fungi and termite. However, these organic biocides are facing some shortcomings when being introduced into the wood using conventional water-based treatment due to their poor water solubility. Polylactic acid (PLA) was employed to encapsulate chlorothalonil, a poor water solubility fungicide using nanoprecipitation method. The nanocomposites were characterised with dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and ultraviolet–visible (UV-vis) spectroscopy. The analysis results showed that chlorothalonil was successfully encapsulated by PLA. The mean diameter of nanocomposites obtained was 188.3 ± 124 nm with polydispersity index of 0.275 ± 0.01. Rubberwood (Hevea brasiliensis) wooden blocks were treated with 0.025% w/v aqueous suspension of nanocomposites by employing vacuum-pressure treatment. The chemical retention was 8.03 ± 5.6 kg/cm3. The biological efficacy of treated wood against termite and fungi were carried out in accordance with Forest Institute of Malaysia (FRIM) In-House Method AK/A4 (no-choice test) and ASTM D2017, respectively. The dry wooden blocks were exposed to subterranean termite (C. Curvignathus) and two decay fungi (Trametes versicolor and Gloeophyllum trabeum) in accelerated condition for four weeks. The weight loss of wooden blocks that attributed to termite attack was reduced from 9.85 % to 2.16%. In addition, the nanocomposites also reduced the weight loss attributed to brown rot fungi (Gloeophyllum trabeum) from 36.73% to 13.13%. Nonetheless, the nanocomposites did not exhibit resistance against white rot fungi (Trametes versicolor). In short, the biological efficacy test has proven that the treatment with low concentration of prepared nanocomposites were sufficient to enhance the resistance of wood against decay fungi and termite.


Keywords: encapsulation, nanoprecipitation, polylactic acid, chlorothalonil, rubberwood

Conference: 18-04-29/05-03 Johannesburg, South Africa


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