Preparation of TTO/UF resin microcapsule via in situ polymerisation and modelling of its slow release

For slow release of tea tree oil (TTO), TTO were encapsulated by urea-formaldehyde (UF) resin via in situ polymerisation. The effects of curing time and drying condition on particle size, and TTO loading of the TTO/UF microcapsules were investigated. The results indicated that TTO/UF resin microcapsules with curing time of 80 min had narrow size distribution and good wall cover. Drying at ambient was better to maintain the TTO content than drying at oven. The loading of TTO with curing time of 80 min can be up to 45 wt.% of the mass-proportion to the prepared microcapsules, and more than 90 wt.% of the loaded TTO could be sustainably released in about 5 days. Moreover, the release kinetics of TTO/UF microcapsules was well described by Ritger-Peppas model, revealing non-Fickian diffusion. Promisingly, TTO/UF microcapsules with good stability can be used as a slow release vehicle for antibacterial application.