Modeling Approach To Assess Clustering Impact on Release Rates of Pesticides from Microencapsulated Products

Abstract

The pesticide release rate from polymer-encapsulated microcapsules is controlled by diffusion across the polymer membrane, membrane thickness, and pesticide loading. However, conditions for microcapsule clustering following conventional application practices and the impact of clustering on the overall release rate are often ignored. Microcapsules are delivered to target surfaces using water droplets as a carrier, and capillary-driven velocities arise within the deposited sessile drop as the water evaporates. This work describes experimental observations and a quasi-static mathematical approach used to elucidate microcapsule clusters that remain following the drop-drying process, along with the anticipated patterns for pesticide release as a function of cluster geometries. The dynamic behavior of a drying sessile drop was modeled as a trajectory of constrained quasi-static equilibrium shapes having a fixed contact line. Observed monolayer clustering of microcapsules was a function of the initial contact angle and size of the sessile drop, evaporation rate, and the microcapsule number density within the drop. The net pesticide release rate from microcapsule clusters was calculated from superposition of smaller decomposed cluster geometries for which release rates were determined by numerical solution to the mass balance governing equation, thereby coupling the self-assembly of microcapsule and microcapsule clustering with environmental release rate predictions.

Microencapsulation of essential oils with biodegradable polymeric carriers for cosmetic applications

“…Nevertheless, the release of the active agent from delivery systems can be classified based on other mechanisms, such as, erosion (the product gradually dissolves in membrane shell), diffusion (the oil diffuses out of delivery system), extraction (mechanical forces during chewing or processing enlarge area of oil) and burst (a reservoir system ruptures under influence of mechanical or osmotic forces) [115]. Several diffusion models have been proposed in the literature to describe the release of an active agent from microcapsules [86,[116][117][118][119][120][121][122][123]. Table 5 presents a summary of the model release related to the diffusion of active agents through the polymeric membranes of microcapsules.…”

Preparation and characterization of enzyme-responsive emamectin benzoate microcapsules based on a copolymer matrix of silica–epichlorohydrin–carboxymethylcellulose

“…[12][13][14][15] Due to the conservation and selective permeation properties of semi-permeable membranes, the use of pesticide microcapsules has been widely applied. [16][17][18][19][20] However, the active ingredient release of the existing pesticide microcapsules occurs typically through passive diffusion release, erosion of the capsule wall, or active diffusion via osmotic pressure, which results in poor control of the release of the core materials. Therefore, the development of new and advanced stimuli-responsive pesticide microcapsules with intelligently controlled release by internal and external stimuli has broad prospects.…”

Matrix-Based Fertilizers Reduce Pesticide Leaching in Soil

“…Commercial slow-release pesticide formulations have been encapsulated with a hydrophobic barrier often from various styrene compounds, combined with mono-or di-carboxylic acids anhydride carboxyl groups. These carboxyl groups are crosslinked with aromatic amines, aliphatic amines, and aromatic isocyanates (Asrar et al 2004;Cryer and Wilson, 2009). Celis et al (2005) tested the efficacy of organoclays to bind hexazinone to reduce offsite movement of pesticides in soil.…”