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April 21, 2016

2 Min Read
Wonder mineral displays multiple functionalities as a plastic additive

Mined in the state of Utah, halloysite possesses a structure that resembles hollow carbon nanotubes. Supplier Applied Minerals (New York, NY) has been marketing the material as a plastic additive capable of various functionalities under its Dragonite brand since 2009 and at the recent Plastic Japan in Tokyo, company President and CEO Andre Zeitoun gave PlasticsToday an update on application development.

Naturally-occurring halloysite possesses a carbon nanotube-like structure, with typical dimensions of 0.2-2.0 μm in length, a 15-30-nm inside diameter, and a 50-70-nm outside diameter.

The hollow tubular mineral acts as a nucleating agent not only for polypropylene (PP) but also for high-density polyethylene (HDPE) and has been demonstrated to reduce cycle times in injection-molded parts by 25% for HDPE using a 1% dosage for an overall cost saving per part of 11% according to Applied Minerals. The Dragonite-HP grade can also be used in rotomolding applications where a similar 1% dosage allows a 15% reduction in cycle time and a 16% weight reduction through thinwalling.

Dragonite also exhibits a nucleating effect in a dosage of 0.5–1% in film extrusion and blow molding applications. Transparent films, for example can be extruded up to 30% faster according to Zeitoun. Further, adding Dragonite to polyolefin foam sheet serves to nucleate the foaming process, while increasing stiffness by 20% without adversely affecting impact strength.

Another functionality of halloysite is flame retardance. The mineral acts as a synergist for alumina trihydrate (ATH) or magnesium hydroxide (MDH) halogen-free flame retardants. “Adding 5% Dragonite-HP:A allows you to remove 10% of the primary flame retardant, thereby reducing overall loading to 55%,” says Zeitoun. “You can also reduce antimony trioxide (ATO) flame retardant synergist loading from 5% down to 1.25% by adding 3.75% Dragonite.”

Dragonite can also be utilized as an encapsulant to extend the life of antioxidants, for example, within a polymer by acting as a time release agent. “We’ve also developed Dragonite as a carrier for slip aid masterbatches to restrict migration from the masterbatch prior to usage,” adds Zeitoun

Halloysite can also be used as a reinforcing additive for thermoset resins such as epoxy, where it can improve impact resistance in certain epoxy systems by up to 400% with just a 2% dosage.

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