Compounding World Forum | event review
(SWCNTs) form an electrically conductive network at ultra-low concentrations, making them effective for conductive and electrostatic dissipative applications, explained Christian Maus, Development and Support Leader at the company. OCSiAl’s SWCNTs are optimally dispersed by using a two-step melt-mixing process that involves making a masterbatch that is then diluted using a twin-screw extruder to formulate a compound. The company said it supplies masterbatches in PP and PE now and is developing masterbatches in other polymers. Heroflon’s Herolub fluorinated micro-powder additives
(FMA) are produced by irradiating and milling polytetra- fluoroethylene (PTFE) so that it chemically bonds with a host polymer. This improves mechanical properties as well as tribological properties such as coefficient of friction, lubrication, and wear-resistance, said Salvatore Alvoisio, General Manager at Heroflon USA.
Bio-based developments Interest in bio-based polymers and bio-based fillers and reinforcing additives is currently at a high level. Don Beuke, Technical Development Leader at Mitsui Plastics, described the use of BioPBS, a biodegradable and bio-based polymer produced by PTTMC Biochem, a joint venture of PTT and Mitsubishi Chemical. Although the polymer’s largest market is paper coating, it can be used in flexible packaging and mulching films and Beuke said BioPBS is also a good modifier for PLA. Mitsui also distributes Bylox, a bio-based filler from Genarex that works well in BioPBS and PBS/PLA blends. The filler has a round particle shape, similar to calcium carbonate, but is lighter in weight. A higher-temperature version, Bylox HT, is thermally stable up to 275 °C. Growth in natural-fibre reinforced compounds for
automotive composites is being driven by the need for weight reduction, said Jeremy Warnes, Business Development Manager at Scion. While many of these compounds incorporate agricultural fibres (such as flax or kenaf), he said softwood fibres from wood pulp have emerged over the past five years as an alternative that offers a more consistent supply without odour issues. Woodforce fibres, from Scion and Sonae, are supplied in an easily dispersible wood fibre dice form. Warnes explained there are some processing challenges for all natural fibres; screw configuration and processing variables must be designed to avoid burning and vent moisture, for example. Performance Biofilaments is a biomaterials
company that is commercialising a technology from FPInnovations for cellulose filaments, which are very high aspect ratio particles produced by delaminating Northern Bleached Softwood Kraft (NBSK) wood fibres.
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Gurminder Minhas, Managing Director at Performance Biofilaments, described NBSK/cellulose filament blends in which the cellulose filaments reinforced the NBSK fibers and produced PP compounds with mechanical properties said to be competitive with glass-fibre reinforced compounds.
Processing improvements There are many aspects to optimising the compounding process. Andy Hoffman, Manager of Entek’s pilot plant, explained the use of side feeders to add fragile fillers after the polymer is melted and the use of vent stuffers to ensure that vents remain open. Andy Kovats, Senior Application Engineer at Brabender Technologie, explained that liquid loss-in-weight feeders are typically designed for a specific application. For example, parameters such as viscosity, lubricity, and corrosivity affect the pump design. The feed rate determines the pump size and affects the selection of the load cell. Although the refill process is not as critical for liquids as it is for solids because the bulk density of the liquid does not change, it is still important to determine the optimal refill rate and to properly size the weigh tank, he explained. Eric Procunier, Product Development Manager for
Sun Plastech, which manufactures ASACLEAN Purging Compound, dispelled some common myths about purging and explained how commercial purging compounds are engineered to clean screws and barrels as well as seal the screw during shutdowns to prevent material from oxidising and depositing on the screw. Special commercial purging compounds are designed to both clean and reduce screw pull force, which he said is particularly beneficial for compounders who often pull screws to change to a different screw designs. Compounders are well aware that screw and barrel
design can be used to optimise mixing and dispersion. Paul Martin, Vice-President of Japan Steel Works (JSW) America, described JSW’s Nippon Intensive Cylinder
Left: OCSiAl’s Christian Maus discussed electrical conductivity modification using SWCNTs
Softwood fibre reinforcements were addressed by Scion’s Jeremy Warnes
January 2017 | COMPOUNDING WORLD 77
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