additives | Functional fillers
bonding with the polymer matrix. The company is also working to bring lower density, higher strength grades to the market, as well as smaller particle size products with a whiter appearance.
Fillers for 3D print 3D printing—or additive manufacturing—can produce complex geometries without the need for moulds or dies, allowing fast production of prototypes and individualised products. However, processing is slow and surface qualities can be less than optimal. The key goals for 3D print system developers is to speed up the process and to improve quality to minimise the amount of post-production processing required. Speaking at the AMI Compounding World Congress
Above: Bags of silica on the filling line at the Huber Engineered Materials plant at Havre de Grace in the US
traditional mineral fillers, engineered glass micro- spheres lower the viscosity of most compounds, acting as miniature internal ball bearings to improve flow. When used in combination with fibres or other particle shapes, mould flow is improved, thus reducing product defects and potentially improving production rates.” Microspheres are available as solid or hollow
spheres. “Functionally, hollow and solid engineered glass microspheres perform in similar ways in thermo- plastics,” Barger says. “Solid engineered glass microspheres at 2.5 g/cc density will improve part performance without weight reduction. Hollow engi- neered glass microspheres (< 1.0 g/cc) offer volume displacement and significant part density reduction.” Aside from density reduction, hollow glass beads are also being considered to improve thermal insulation properties, he says. The glass spheres also have less effect on colour than some tinted mineral fillers. In thermoplastic processing, hollow engineered
glass microspheres demonstrate enough strength to withstand vigorous process conditions without degrada- tion. Compounding is also said to be straightforward. “Due to the smooth, spherical shape of engineered glass microspheres, they require less work to be compounded into resins than angular, irregular, or platelet particles. The engineered glass microspheres have a comparatively low surface area, which keeps working viscosity lower at higher loading levels as well as provides very low resin demand,” Barger says. “Engineered glass materials are extremely durable and capable of handling all types of compounding, yet since they are spherical in shape, they will process less harshly and extend equipment life.” Barger says Potters’ future development work is
focused on development of additional engineered glass microspheres with adhesion promoters to enhance
60 COMPOUNDING WORLD | August 2017
in Cologne, Germany, in April 2017, Péter Sebö, Head of Marketing and Market Development at HPF The Mineral Engineers (a division of Quarzwerke Group) described work it has undertaken to develop a new functional- filler-based masterbatch designed for 3D printing. The type of polymer used for 3D printing depends in part on the printing technology; HPF first focused on fused deposition modeling (FDM) – also called fused filament fabrication (FFF) – and experimented with ABS and a variety of fillers including wollastonite, mica, kaolin, and others. “The minerals are not just the standard ones; you have to adjust the particle size, the shape, and the surface modification, such as a coating,” says Sebö. “One of the key requirements, especially concerning filament printing, is constant grain size distribution due to the diameter of the die,” he said. HPF also developed hybrid filler blends with special properties, which are now available to resin or compound producers as well as in ready-to-use masterbatches for filament extruders. Adding fillers is said to have achieved reduced shrinkage and warpage in printed parts. The next step, says Sebö, is to improve the mechanics of the final part and the adhesion of the layers; HPF is seeking polymer material producers to collaborate on these projects. In addition to FDM, HPF has also experimented with
photopolymers based on epoxy and acrylic for use in the stereolithography (SL) additive manufacturing process. In the coming months, the company will also run experiments with PA6, PA12, and PLA using FDM and will widen its activities to include selective laser sintering (SLS) using PA12 and PA6 materials.
Click on the links for more information: ❙
www.imerystalc.com ❙
www.imifabi.com ❙
www.hubermaterials.com ❙
www.pottersbeads.com ❙
www.hpfminerals.com
www.compoundingworld.com
PHOTO: HUBER ENGINEERED MATERIALS
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