Nanoparticle-in-Wax Dispersions – Make Stable Formulations!

Dispersing nanoparticles into wax matrices is an important, yet challenging application in coatings, cosmetics, pharmaceuticals, and phase-change materials. Given the intrinsic viscosity of molten waxes, their hydrophobicity, and the tendency of nanoparticles to agglomerate due to high surface energies, the preparation of nanoparticle-wax dispersion requires know-how. Hielscher sonicators provide the dispersing power, precise controllability and scalability for the production of stable nanoparticle-wax dispersions in bench-top and industrial production.

Challenges in Nanoparticle Dispersion into Wax

Nanoparticles – whether metallic, ceramic, or carbon-based – readily form aggregates due to strong van der Waals interactions. In wax, these interactions are exacerbated by the lack of polar solvents or stabilizers. Mechanical stirring or rotor-stator homogenizers often prove insufficient, especially when nanoparticles are below 100 nm in diameter or when high loadings are required. A homogeneous dispersion demands an energy input capable of breaking apart agglomerates at the nanoscale while simultaneously wetting the particle surface with the wax medium.

Mechanism of Ultrasonic Nano-Dispersion

The significant effectiveness of ultrasonic dispersion lies in the unique working mechanism of acoustic cavitation. Probe-type sonicators generate intense cavitational forces when high-intensity, low-frequency ultrasound waves propagate through liquid, e.g., molten wax. Bubble collapse during cavitation produces localized hotspots with extreme shear gradients, shock waves, and microjets. These transient forces overcome interparticle adhesion and efficiently deagglomerate nanoparticle clusters.
In addition, ultrasonication enhances wetting of nanoparticle surfaces by the wax melt. The repeated collapse of cavitation bubbles reduces interfacial tension, enabling wax molecules to penetrate between particles and stabilize them sterically.

Applications for Ultrasonically-Prepared Wax Nanodispersions

The ability to homogeneously disperse nanoparticles in wax opens the ways for manifold applications:

• Coatings and polishes: Addition of silica or alumina nanoparticles enhances hardness, scratch resistance, and gloss.
• Cosmetic formulations: Titanium dioxide or zinc oxide nanoparticles impart UV protection, while maintaining transparency.
• Phase-change materials (PCMs): Graphene, carbon nanotubes, or metal oxides increase thermal conductivity, improving heat storage efficiency in energy systems.
• Drug delivery: Lipophilic nanoparticles embedded in wax act as slow-release reservoirs in topical or oral formulations.

Ultrasonic Dispersers for Wax-Nanoparticle Formulations

Ultrasonic dispersing using with Hielscher high-performance probe-type sonicators is a robust and scalable technique for the production of stable wax nano-dispersions.
Hielscher probe-type ultrasonic systems are widely used for nanoparticle processing due to their high processing capability, precise parameter control, and linear scalability. Whether you need to prepare wax nanoparticle dispersions in batch or in continuous inline production, Hielscher Ultrasonics offers the ideal sonication setup: ultrasonic lab homogenizers are the perfect tool for research and product development, whilst ultrasonic industrial flow cells allow for the production of stable wax nano-dispersions fulfilling highest quality standards.
Built to the highest quality standards, Hielscher ultrasonicators combine robustness, user-friendliness, and easy integration into industrial processes. Designed to withstand demanding environments, they feature state-of-the-art technology, are ISO certified, and comply with CE, UL, CSA, and RoHS requirements.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

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