ADDITIVES | FUNCTIONAL FILLERS
Development specialist Dr Friedrich Wolff. “For thermoplastic applications the Glass Bubbles grade iM16k is typically the material of choice. Its main key features are a low density of 0.46 g/cm³, an isostatic crush strength of 1,100 bar and a median diameter of 20 microns,” he says. US compounder RTP Company is using glass
sphere technology in its LT (Light and Tough) series of PP, PA and PBT compounds, which it introduced earlier this year to provide “drop-in” part weight savings of 5-10% with minimal loss of me- chanicals compared to traditional glass reinforced grades (Figure 4). Senior Product Development Engineer
Structural Products Karl Hoppe says the new grades have resulted from develop- ments in the strength of the glass spheres and optimisation of the compounding process, which has minimised breakage. “Previously with spheres we focused on maximis- ing the weight saving but you lost the properties,” Hoppe says. “The LT compounds are target- ing the same properties that customers want with 30% glass filled PP or PA.”
Above: Wine bottle stoppers are a relatively new applica- tion for
AkzoNobel’s Expancel microspheres
Polymer microspheres Akzo Nobel also makes microspheres, but of thermoplastic rather than glass. Its Expancel microspheres consist of a polymer shell – a copolymer based on acrylonitrile and methlymeth- acrylate – encapsulating a gas. When the micro- spheres heat up during processing, the internal pressure from the gas increases and the shell softens, resulting in a dramatic increase of the volume of the microspheres. The gas remains inside the spheres.
Figure 3: Effect of different fillers on melt viscosity showing that glass microspheres allow higher loading levels when compared to other fillers, providing greater flexibility in formulation and greater resin extension Source: Potters Engineered Glass Materials
“The main reason why our customers are using Expancel microspheres in thermoplastic applica- tions is – beside the fact to reduce density and in many cases the costs of the end product – that it is possible to achieve a non-visible closed cell-struc- ture,” says Klaus Rosskothen, Key Account Manager for Expancel. “A quite new application is the use of microspheres in food applications, for example thermoplastic wine stoppers.” Akzo Nobel offers grades that fulfil the requirements of regulations for food packaging, he says. “The main reason for using Expancel in wine stoppers is the improved sealing properties. When the stoppers are squeezed into the bottle, the spheres are squeezed as well. But the gas inside provides a counter-pressure that improves the sealing properties. The stoppers are mostly produced in PE and EVA,” he says. “Expancel microspheres can be used in all kinds of thermo- plastic applications, as long as the process param- eters – process temperature and time for example – allow for their use.”
Figure 4: Tensile strength and density of 30% glass reinforced PP, PA66 and PBT compounds against LT equivalents with glass microsphere reinforcement Source: RTP Company
64 COMPOUNDING WORLD | August 2018
CLICK ON THE LINKS FOR MORE INFORMATION: �
www.arcticminerals.com �
www.hubermaterials.com �
www.imerys.com �
www.imifabi.com �
www.hybridplastics.com �
www.resinenterprise.com �
www.pqcorp.com (Potters) �
www.3m.com �
www.aschulman.com �
www.rtpcompany.com �
www.expancel.akzonobel.com
www.compoundingworld.com
PHOTO: AKZONOBEL
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