TECHNOLOGY | FUNCTIONAL FILLERS


“The stiffness is significantly increased by using our needle-shaped fillers and the impact strength can be improved by using our blocky additives. In addition, these effects can be further enhanced by using suitable surface coatings,” he says. The company’s Trefil phlogopite mica can be used to improve thermal and mechanical proper- ties in PLA compounds, says Sebö. What results is much reduced and more isotropic shrinkage, increased tensile strength and tensile modulus, and higher rigidity with no cost in toughness.


Above: Talc is established as the workhorse filler for plastics


Steamic provide improved processing and crystal- lisation speed along with increased stiffness and enhanced temperature resistance. Imerys also offers specific calcium carbonate grades for maximising processing, optical, and mechanical properties of bioplastics films, while reducing cost.” For both flexible and rigid compostable applica-


tions, talc plays a functional role and especially in PLA based applications, says IMI Fabi’s Malacari. He references a special talc grade, EcoFill, which he says meets the demanding requirements of food contact compostable applications, especially where relatively high temperature environments are in use. “High mineral purity and extremely enhanced lamellarity make EcoFill a new generation additive for such fast developing applications,” he says. Biopolymers are also in the spotlight at the HPF


The Mineral Engineers division of Quarzwerke. Bio-based polymers such as PLA have the potential to be used in a broad range of applications, “but the required property profiles can often not be met by the biopolymers alone,” says Péter Sebö, Head of Marketing & Market Development. Sebö says studies at HPF show that different high-performance mineral fillers, including wollas- tonite, kaolin, and micas, open up various possibili- ties for property modification in PLA compounds.


The appeal of mica Phlogopite micas are also available from Arctic Minerals under the ThermaFlex tradename. DeArmitt says micas can provide a step up from talcs in several cases, not just for compounds based on biopolymers. For many years, talc has been a workhorse reinforcement, and much has been done to improve its aspect ratio to eke out the last drop of performance, he says. “As talc reaches its limits, people are looking more at ultra-pure, specially-milled mica, which can give even higher aspect ratio with a concomitant boost in strength and stiffness. For automotive customers, that means lightweight and better gas mileage.” Huber Engineered Materials is another compa- ny highlighting its broad portfolio of fillers, in this case ranging from alumina trihydrate (ATH) and magnesium hydroxide (MDH) to ground calcium carbonate. ATH and MDH are functional fillers that can reduce flame spread and smoke generation in a wide variety of plastic, rubber, adhesive and coating products. But, like other fillers, their presence alters the mechanical properties of the compound. To augment the degradation of properties such as elongation, tensile strength and flexibility, Huber produces a full line of surface- coated ATH and MDH products (Table 1). Huber says its newest surface treated halogen-


free products are Magnifin H-5 TV and H-10 TV magnesium hydroxides. Compared to other MDH products, they offer higher elongation (Figure 1),


Table 1: Typical compound processing and performance gains resulting from various filler surface treatments Surface Coating Type


Effect Stearic acid


Non-functional silane Amino functional silane Vinyl functional silane Epoxy functional silane Proprietary coatings Source: Huber


34


Faster incorporation, lubricity, reduced degradation, often used in PVC Hydrophobicity, improved elongation, higher loadings at lower viscosity Improved balance of tensile, elongation and flexibility in polyamide Improved balance of tensile, elongation and flexibility in polyolefin and silicone Improved cohesive strength in thermoset systems


Improved mechanical properties after heat aging, improved fire retardance COMPOUNDING WORLD | June 2020 www.compoundingworld.com


IMAGE: SHUTTERSTOCK


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