Formation and Mechanical Characterization of Aminoplast Core/Shell Microcapsules

Abstract

This work aims at establishing a link between process conditions and resulting micromechanical properties for aminoplast core/shell microcapsules. The investigated capsules were produced by the in situ polymerization of melamine formaldehyde resins, which represents a widely used and industrially relevant approach in the field of microencapsulation. Within our study, we present a quantitative morphological analysis of the capsules' size and shell thickness. The diameter of the investigated capsules ranged from 10 to 50 μm and the shell thickness was found in a range between 50 and 200 nm. As key parameter for the control of the shell thickness, we identified the amount of amino resin per total surface area of the dispersed phase. Mechanical properties were investigated using small deformations on the order of the shell thickness by atomic force microscopy with a colloidal probe setup. The obtained capsule stiffness increased with an increasing shell thickness from 2 to 30 N/m and thus showed the same trend on the process parameters as the shell thickness. A simple analytical model was adopted to explain the relation between capsules' geometry and mechanics and to estimate the elastic modulus of the shell about 1.7 GPa. Thus, this work provides strategies for a rational design of microcapsule mechanics.

Preparation and characterisation of user-friendly PMMA microcapsules for consumer care

“…Statistical analysis of the size distributions shows that they can be fitted by Gaussian, with 95% confidence, and there is no significant difference in the size distribution between the oil droplets and microcapsules for each emulsification method. The mean diameter of the microcapsules produced using homogenization is 44.8 ± 0.7 ȝm, slightly smaller than that using membrane emulsification but it could be modified if required [14][15]. Crucially, the CV and SPAN values of the microcapsules made using homogenization are 34.4 ± 0.2 % and 1.12 ± 0.06, which are significantly greater than those using the membrane emulsification.…”

“…For compression of single thin-shell capsules, such as MF [10,[14][15][16][17], the force typically drops to zero after their bursting. Also PMMA microcapsules formed after a polymerisation time of 1 h in this study had the similar bursting behaviour to MF.…”

Formaldehyde-free melamine microcapsules as core/shell delivery systems for encapsulation of volatile active ingredients

“…7,12,13,21 Due to the low cost and the ready availability of the starting materials, to the high yield of encapsulation, and to the mechanical properties of the resulting polymer shells, urea or melamine-formaldehyde microcapsules obtained from aminoplast resins have been developed in various applications, including home care consumer goods. 7 These resins are usually polymerized to form the shell under acidic conditions.…”

Fabrication and Characterization of PMMA/HMX-based Microcapsules via in situ Polymerization

“…Until now, micro-encapsulation has aroused increasing interest and has been frequently used whenever the functionality of an active substance needs to be protected or a controlled release is required [10,11]. Researchers from different study groups have adopted recrystallization or coating technologies to desensitize existing explosives [12][13][14][15], and several strategies have been developed for the creation of polymer coated core-shell microcapsules, but the most commonly applied and industrially relevant method is in situ polymerization [16,17].…”