Amino resin microcapsules. IV. Surface tension of the resins and mechanism of capsule formation

Dietrich, K.; Bonatz, E.; Nastke, R.; Herma, H.; Walter, Marie V.; Teige, W.

doi:10.1002/actp.1990.010410205

Cited by 28 publications

(17 citation statements)

References 3 publications

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“…For the calculation of the theoretical mean droplet diameters first of all the interfacial tension between the resin solution and tetradecane was measured. The interfacial tension at 60°C was found to be 11.2 ± 0.4 mN m −1 ( c resin = 50 g L −1 ) which is close to an interfacial tension of 8.6 mN m −1 for a triethanolamine modified melamine/formaldehyde resin (0.05 mol triethanolamine per mol melamine, measured at 20°C against xylene) published by Dietrich et al10 The interfacial tension together with the stirrer diameter ( L = 9 × 10 −3 m), the density of the liquid ρ f = 931 kg/m 3 and the phase volume fraction of 0.43 was used to calculate the Sauter diameter in dependence of the stirrer speed (Fig. 8).…”

Section: Resultssupporting

confidence: 80%

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

Sgraja

Blömer

Bertling

et al. 2008

J of Applied Polymer Sci

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Microcapsules of tetradecane enclosed by a polymeric wall of amino resin were synthesized by the in situ polymerization using melamine-formaldehyde precondensates. It was found that resin concentrations of 60-240 g L -1 for a phase volume fraction of 0.14 and 0.29 and concentrations of 50-240 g L -1 for a phase volume fraction of 0.43 lead to stable microcapsules. Furthermore, the dependence of the shell thickness from the resin concentration for a phase volume fraction of 0.29 was investigated whereas the shell thickness was calculated from the density and the mean diameter of the capsules. It was found that below a concentration of 100 g L 21 the density and thus the shell thickness increases linear with the resin concentration whereas at higher concentrations it almost remains constant and only the amount of the resin precipitated in solution increases. Additionally, it was shown that the mean droplet size (which is almost equal to the capsule size) in dependence of the stirring speed can be derived from the theory of droplet disruption. Thereby the coherence beginning with the stirring speed and the mean diameter to the total surface and the shell thickness is described.

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Section: Resultssupporting

confidence: 80%

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

Sgraja

Blömer

Bertling

et al. 2008

J of Applied Polymer Sci

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“…Melamine can react with aldehydes to give aminoplast copolymers. 27,28 In the presence of 2,2-dimethoxyacetaldehyde (DME or 1, Fig. 1), this polymerization can be controlled by the pH as observed with formaldehyde.…”

Section: Resultsmentioning

confidence: 99%

“…7 These resins are usually polymerized to form the shell under acidic conditions. 27,28 The high valency of melamine leads to highly cross-linked barrier materials at the oil-water interface. 13 The main drawback of melamine-formaldehyde resins and capsules is the capability of these materials to release formaldehyde.…”

Section: 2122mentioning

confidence: 99%

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

et al. 2017

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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.

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“…The polycondensation of the amino resin occurs in the continuous phase, and the phase separation is linked to the pH and the melamine-formaldehyde molar ratio. [23][24][25][26][27][28] Finally, the objective of this research is the evaluation of Melaleuca alternifolia (tea tree) oil as natural antimicrobial agent and its microencapsulation for footwear applications, including the study of the effect of some variables, such as the oil to polymer ratio, upon the characteristics of microcapsules.…”

Section: Introductionmentioning

confidence: 99%

Microencapsulation ofMelaleuca alternifolia(Tea Tree) Oil as Biocide for Footwear Applications

Sánchez-Navarro

Cuesta-Garrote

Arán-Aı́s

et al. 2011

Journal of Dispersion Science and Technology

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Functional materials with antimicrobial properties are being investigated in order to provide shoes with new properties and added value by incorporating natural antimicrobial agents to conventional materials (leather, fabrics, foams, etc). Microencapsulation is an effective method to protect these functional natural biocides from reactions with moisture, light, and oxygen. If a footwear material is treated with microencapsulated biocide agents, higher durability of functionality is expected. This article reports the evaluation of Melaleuca alternifolia (tea tree) oil which is a natural essential oil, as an antimicrobial agent for footwear application. Furthermore, microcapsules containing this essential oil were synthesized by in situ polymerization method using a melamine-formaldehyde resin as shell material in order to increase the durability of this natural biocide in footwear materials. Microcapsule characterization, such as particle size, morphology, and chemical properties was carried out for different oil to polymer ratios. Finally, the incorporation of the microencapsulated biocides into different footwear materials was also evaluated.

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Amino resin microcapsules. IV. Surface tension of the resins and mechanism of capsule formation

Cited by 28 publications

References 3 publications

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

In situ encapsulation of tetradecane droplets in oil‐in‐water emulsions using amino resins

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

Microencapsulation ofMelaleuca alternifolia(Tea Tree) Oil as Biocide for Footwear Applications

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