MACHINERY | ALTERNATIVE EXTRUDERS
Images show dispersion quality for 0.5% BaSO4 nanoparticles added as powder and in liquid suspension using
Gneuss Nano Compounding
Source: Gneuss
low wear on the machinery side achieved in the compounding process. This results in the overall cost of production being particularly attractive,” he says.
Dispersion gains Gneuss claims that its MRS Extruder is particularly well suited to specialty compounding tasks. “As a result of the extremely homogeneous distribution of particles in the MRS Extruder, it is possible to introduce the smallest particles in polymers via a suspension,” says Andrea Kossmann, Marketing Manager. “Consequently, it is possible to make major reductions in the quantity of additive needed to achieve the required results. This has the additional advantage of making the polymer easier to recycle.”
Achieving this high level of distribution requires
a different approach. “Currently, many additives are introduced into polymers in powder form. Around 20% of powder (by weight) consists of agglomer- ates, which reduces the active surface area of the additive. The effectiveness of the additive particles is in relation to their active surface area. Therefore, the proportion of additive needed should not only be determined by weight. If the size of the additive particles can be reduced, then the quantity by weight can also be considerably reduced,” he says. Kossmann says this not only reduces the cost but
increases recycling possibilities as, if the additive level used is too high, it is not always possible to reprocess the polymer. Being able to effectively incorporate smaller, nano-scale particles can also result in high value recycled products with an acceptable margin. “In order to use additives with an extremely small size distribution, it is necessary to include them in a liquid suspension before working them into the polymer. Only in this way can agglomer- ates be avoided, so that the particles remain as individual particles. As a result, if the combined
30 COMPOUNDING WORLD | October 2020
surface area of all the individual, separate parti- cles can be increased, then the quantity of particles for the required effect can reduced significantly,” he says. The MRS Extruder is a key element in the Gneuss
Nano Compounding Technology for incorporation of nano-particles into polymer melts. Nano particles in powder form with a high proportion of agglomerates have the disadvantage that the potential total area offered by the nano particles cannot be realised and the potential positive benefits to the polymer are often not obtained. The Nano Compounding Technology is an industrial scale process that permits the introduction of individual nano particles into polymers without agglomerates and with completely safe handling.
Nano suspension Kossmann says the introduction of nano particles (less than 100 nm) into polymers takes place by means of a liquid suspension, in which the particles are safely contained so cannot get into the environ- ment. After the polymer is plasticised, it flows through a mixing and hydrolysis chamber where the suspension is injected into the polymer under pressure. The mixture of polymer and suspension flows on into the devolatilising MRS Extruder. This extruder is designed so that, with a mixture of polymer greater than 70% and suspension less than 30%, the suspension is removed in less than five seconds to leave the nano particles completely embedded in the polymer. Because of the ex- tremely fast extraction of the liquid suspension carrier, there is practically no damage to the polymer, Gneuss says. The company adds that nano-scale additives are
characterised by extremely high surface area in relation to their mass. Depending on the additive, this permits a range of significant changes to the properties of the finished compound. These include modification of the crystallisation tempera-
www.compoundingworld.com
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