• Reinforced rubbers show higher tensile strength, elongation, abrasion resistance and better aging stability.
• Fillers such as carbon black (e.g. CNTs, MWNTs), graphene, or silica must be homogeneously dispersed in the matrix to provide the desired material properties.
• Power ultrasonics gives superior distribution quality of monodispersed nanoparticles with highly reinforcing properties.

Ultrasonic Dispersion

Ultrasonication is widely employed for dispersing nano materials such as monodispersed nanoparticles and nanotubes, since ultrasonics enhances separation and functionalization of the particles and tubes greatly.
Ultrasonic dispersing equipment creates cavitation and high shear forces to disrupt, deagglomerate, detangle and disperse nano particles and nanotubes. The intensity of sonication can be precisely adjusted and controlled so that the ultrasonic processing parameters are adapted perfectly, taking concentration, agglomeration, and alignment/entanglement of the nano material into account. Thereby, nano materials can be optimally processed regarding their specific material’s requirements. Optimal dispersion conditions due to individually adjusted ultrasonic process parameters result in a high-quality final rubber nanocomposite with superior reinforcing characteristics of the nano-additives and -fillers.
Due to the superior dispersion quality of ultrasonics and the thereby achieved uniform dispersion, a very low filler loading is sufficient to obtain excellent material characteristics.

Ultrasonically Carbon Black-Reinforced Rubber

Carbon black is one of the most important filler in rubbers, especially for tires, to give the rubber material abrasion resistance and tensile strength. Carbon black particles are heavily prone to form aggregates which are difficult to disperse homogeneously. Carbon black is commonly used in paints, enamels, printing inks, nylon and plastic colorings, latex mixtures, wax mixtures, photo coatings, and more.
Ultrasonic dispersion allows to deagglomerate and blend uniformly with a very high monodispersity of the particles.
Click here to learn more about ultrasonic dispersion for reinforced composites!

Ultrasonically CNT- / MWCNT-Reinforced Rubber

Ultrasonic homogenizers are powerful dispersing systems which can be precisely controlled and adjusted to the process and material requirements. The precise control of the ultrasonic process parameters is especially important for dispersing nanotubes such as MWNTs or SWNTs since the nanotubes must be detangled into single tubes without being damaged (e.g. scission). Undamaged nanotubes offer a high aspect ratio (up to 132,000,000:1) so that they give exceptional strength and stiffness when formulated into a composite. Powerful, precisely adjusted sonication overcomes the Van der Waals forces and disperses and detangles the nanotubes resulting in a high performance rubber material with exceptional tensile strength and elastic modulus.
Furthermore, ultrasonic functionalization is used to modify carbon nanotubes in order to attain desired properties that can be used in manifold applications.

Ultrasonically Nano-Silica-Reinforced Rubber

Ultrasonic dispersers deliver a highly uniform particle distribution of silica (SiO₂) nano particles in rubber polymer solutions. Silica (SiO₂) nano particles must be homogeneously distributed as mono-dispersed particles in polymerized styrene-butadiene and other rubbers. Mono-dispersed nano-SiO₂ acts as reinforcing agents, that improves toughness, strength, elongation, bending and anti-aging performance, significantly. For nano particles applies: The smaller the particle size, the larger is the specific surface area of the particles. With a higher surface area/volume (S/V) ratio, better structural and reinforcing effects are obtained, which increases the tensile strength and hardness of rubber products.
Ultrasonic dispersion of silica nano particles allows to control the process parameters exactly so that a spherical morphology, precisely adjusted particle size, and very narrow size distribution is obtained.
Ultrasonically dispersed silica results in highest material performance of thereby reinforced rubber.
Click here to learn more about the ultrasonic dispersing of SiO₂!

Ultrasonically Dispersion of Reinforcing Additives

Sonication has been proven to disperse many other nanoparticulated materials to improve modulus, tensile strength, and fatigue properties of rubber composites. Since particle size, shape, surface area and surface activity of fillers and reinforcing additives are crucial for their performance, powerful and reliable ultrasonic dispersers are one of the most frequently used methods to formulate micro- and nano-sized particles into rubber products.
Typical additives and fillers, which are incorporated by sonication as uniformly distributed or monodispersed particles in rubber matrices, are calcium carbonate, kaolin clay, fumed silica, precipitated silica, graphite oxide, graphene, mica, talc, barite, wollastonite, precipitated silicates, fumed silica and diatomite.
When oleic acid-functionalized TiO₂ nanoparticles are ultrasonically dispersed in styrene-butadiene rubber, even a very small amount of the oleic-SiO₂ results in significantly improved modulus, tensile strength, and fatigue properties and functions as protective agent against photo and thermo degradation.

• Alumina trihydrate (Al₂O₃) is added as flame retardant, to improve thermal conductivity, and for tracking and erosion resistance.
• Zinc oxide (ZnO) fillers increase the relative permittivity as well as the thermal conductivity.
• Titanium dioxide (TiO₂) improves thermal and electrical conductivity.
• Calcium carbonate (CaCO₃) is used as additive due to its mechanical, rheological and flame retarding properties.
• Barium titanate (BaTiO₃) increases the thermal stability.
• Graphene and graphene oxide (GO)give superior mechanical, electrical, thermal and optical material characteristics.
• Carbon nanotubes (CNTs) improve mechanical properties such as tensile strength, electrical and thermal conductivity significantly.
• Multi-walled carbon nanotubes (MWNTs) improve Young`s modulus and yield strength. For instance, as little as 1 wt.% of MWNTs into an epoxy result in an increased Young`s modulus and yield strength respectively, 100% and 200%, compared to the pure matrix.
• Single-walled carbon nanotubes (SWNTs) improve mechanical properties and thermal conductivity.
• Carbon nanofibers (CNF) add strength, heat resistance and durability.
• Metallic nanoparticles such as nickel, iron, copper, zinc, aluminium, and silver are added to improve electrical and thermal conductivity.
• Organic nanomaterials such as montmorillonite improve the mechanical and flame retardant properties.

Ultrasonic Dispersion Systems

Hielscher Ultrasonics offers a wide product range of ultrasonic equipment – from smaller bench-top systems for feasibility test up to heavy-duty industrial ultrasonicator units with up to 16kW per unit. Power, reliability, precise controllability as well as their robustness make Hielscher’s ultrasonic dispersing systems the “work horse” in the production line of micron- and nano-particulated formulations. Our ultrasonicators are capable to process aqueous and solvent-based dispersions up to high viscosities (up to 10,000cp) easily. Various sonotrodes (ultrasonic horns), boosters (intensifier/decreaser), flow cell geometries and other accessories allow for the optimal adaption of the ultrasonic disperser to the product and its process requirements.
Hielscher Ultrasonics’ industrial ultrasonic processors can deliver very high amplitudes. Amplitudes of up to 200µm can be continuously run in 24/7 operation promptly. For even higher amplitudes, customized ultrasonic sonotrodes are available. The robustness of Hielscher’s ultrasonic equipment allows for 24/7 operation at heavy duty and in demanding environments. Hielscher`s ultrasonic dispersers are installed worldwide for large-scale commercial production.

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