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

Abstract

The release of volatile bioactive molecules, such as fragrances, can be controlled by microencapsulation in core-shell polymeric delivery systems. Currently, most of the available polymers are based on melamineformaldehyde materials, and the release is generally triggered by the rupture of the brittle and stiff shell.However, formaldehyde-based chemistry may often be undesirable in applications for consumer goods such as personal care products or detergents for fabrics, and there is a strong need for formaldehydefree microcapsules in these applications. In this article, formaldehyde is successfully substituted by glyoxal and its derivatives to allow the polymerization of melamine and other amines to prepare oligomers as starting point for core/shell polymerization. The oligomer synthesis is optimized via the reactant composition and towards an enhanced potential cross-linking density. The formulations with the most branched oligomers are applied at the interface of oil-in-water emulsions to prepare microcapsules. Their capacity to retain volatile molecules is measured by thermogravimetry and their mechanical properties are measured by micromechanical testing using compression-retraction cycles on multiple individual microcapsules. The results reveal an excellent retention capacity for volatile molecules and tunable mechanical properties that make these capsules highly suitable as a formaldehyde-free alternative to conventional aminoplast microcapsules.

Cross-linking of double oil-in-water-in-oil emulsions: A new way for fragrance encapsulation with tunable sustained release

“…Note that polymerization did not induce shrinkage or swelling. The size and size distribution width are governed by the initial double emulsion and they are rather well defined compared to other capsules [39,40]. As a consequence, the expected initial load of fragrance (15wt% with respect to total sample) is the same for all the capsules.…”

“…Alternatively, the pressure could be released and the liquid remaining outside analyzed by GC ( Figure 20 The comparison of the proposed capsules with all the existing ones without focus on the goal and application is just an impossible task in the frame of an original paper. Therefore, the ambitious of this paragraph is limited to a comparison with some recent and novel systems [19,20,23,39,40,[52][53][54][55][56][57][58][59][60][61][62][63]] that aims at reducing or avoiding the use of formaldehyde, most of them being core-shell capsules. Also depending on the considered application, either a provoked sudden release of the cargo is aimed at [19,20,[54][55][56][60][61][62] or, on the contrary, a slow and sustained released is preferred or observed as it was the goal herein [39,40,52].…”

Quantification of Residual Perfume by Py-GC-MS in Fragrance Encapsulate Polymeric Materials Intended for Biodegradation Tests

“…Core shell microcapsules containing fragrance oil were prepared according to literature procedures [10,12,23].…”

“…Different delivery systems have been developed across the years, notably in order to control the kinetic release of odorant molecules, increase storage stability and/or improve deposition on different substrates [4][5][6][7]. Core-shell microcapsules are the most used, thanks to the possibility of perfume release as a result of an external stimulus, e.g., mechanical rubbing [8][9][10], light exposure [11][12][13] temperature [14,15] or pH change [16][17][18]. They consist of a spherical shell of cross-linked polymer (e.g., polyurea, polyurethane, melamine-formaldehyde, polyamides, etc.)…”

Developing Multi Stimuli‐Responsive Core/Shell Microcapsules to Control the Release of Volatile Compounds

“…In the latter case, fragrance release can be triggered by enzymes, changes in temperature or pH, or the action of oxygen or light and combinations thereof (chemical stimulus), whereas in the former case, release is mainly based on the mechanical rupture (e.g., by rubbing) of the delivery system in the application and/or diffusion of the fragrances out of the polymer matrix (physical stimulus). Because of their performance, mechanical properties, and cost‐efficiency, the most common systems that rely on a physical stimulus for fragrance release comprise core/shell microcapsules based on aminoplasts, polyurea/polyurethanes, poly(meth)acrylates, or others prepared by interfacial polymerization, as well as nanoparticles obtained by miniemulsion polymerization of methacrylates and/or styrene . A few encapsulation systems that deliver fragrances in response to temperature, hydrolysis (pH), or light have also been reported.…”