ADDITIVES | FUNCTIONAL FILLERS
with its introduction of DenzFlex, a high purity Fe2
O3
red iron oxide launched earlier this year. DenzFlex is described as a high purity Hematite-
based product and is said to be substantially less expensive than traditional iron oxide offerings, allowing it to compete with barium sulphate. With a thermal conductivity of 1,250 W/(m.K), it may also find application in the production of thermally conductive compounds. It can also provide x-ray and radar blocking and enable microwave heating.
Wollastonite fibres Wollastonite is the dominant mineral filler in the marketplace at present, says DeArmitt, but users are looking for alternatives. Here, Arctic Minerals expects to soon be able to sample a new experimental amorphous mineral fibre product called FibraF- lex. This is said to have a higher aspect ratio than wollastonite – which means it delivers superior mechani- cal properties – but contains no detectable crystalline silica. The main target applications are foreseen as a reinforcement or to provide scratch resistance in PP automotive parts. DeArmitt also highlights the custom milling and surface treatment services offered by Arctic. Mineral
Above: Washing machine
counterweights are a potential application for DenzFlex red iron oxide from Artic Minerals
fillers are often surface treated with dispersants or spoiling agents to confer additional performance. Dispersants can, for example, help provide higher gloss, impact resistance and elongation at break while allowing for higher filler loadings for a given polymer melt viscosity. Coupling agents help retain high temperature and wet mechanical and electri- cal properties of a composite material. Standard options are available but, until now, he says few affordable custom surface treatment options have been on offer. DeArmitt says Arctic has developed a new in-line process that offers a new level of flexibility
Right: Wollastonite fibres could improve scratch resistance of PP automotive interior parts
Figure 1: Particle size distribution of Hubercarb W325 low-silica calcium carbonate Source: Huber
and affordability. The company is now able to mill additives and minerals to tight specifications and surface treat them where needed. It can also offer a low-moisture milling option to produce talc and other minerals with very low levels of water. “This is important for sensitive plastics like polyesters and for cases where venting of moisture during compounding is not possible,” DeArmitt says.
Talc developments Huber Carbonates is another functional filler supplier responding to increasing demand for additives with low levels of crystalline silica. It mines and manufactures an array of ground industrial calcium carbonate grades at three strategic locations in the US: Marble Hill in Geor- gia; Quincy in Illinois; and Marble Falls in Texas. The company has introduced Hubercarb W325, a ground grade of CaCO3
it says is manufactured
from the brightest limestone ore available and offers a silica level of 0.05%. “Consequently, Hubercarb W325 does not require a health warning on its SDS. Other benefits include a consistent particle size at 13 microns along with its white and high brightness appearance,” says a company spokesperson (Figure 1). Imerys Performance Additives Development
Manager, Polymers & Rubber, Anaïs Berjeaud says developments in its talc products are further improving the performance of polymer com- pounds. She says engineering thermoplastics such as PC and PC alloys require a good balance of mechanical properties combined with good surface appearance. “Glass fibre can cause abrasion and poor appearance and mineral solutions used in polycarbonate and PC alloys must have very limited interaction with the PC matrix to prevent deteriora- tion of the polymer and surface appearance issues.” Talc – hydrated magnesium silicate – is the softest of all minerals and provides improved stiffness and
56 COMPOUNDING WORLD | August 2018
www.compoundingworld.com
PHOTO: CHRIS DEARMITT
PHOTO: SHUTTERSTOCK
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