additives | Functional fillers
Right: This SEM image of talc shows the plate-like
structure that gives it its
reinforcing properties
production of high brightness and high purity lamellar talc. The company says it has an annual capacity of more 100,000 tonnes. Talc is not without its challenges for compounders. Prime among these is poor flow due to its fluffy, lamellar structure. This is especially notable for the most highly engineered grades of talc with small particle sizes and narrow particle size distributions, says Malacari. However, he says poor flowability can be overcome using devices designed for handling such powders in the feeding process or, for some applica- tions, by compacting the talc before feeding. IMI Fabi’s HTP1S grade of talc, for instance, is
Below: IMI Fabi’s Mount Seabrook talc mine in Australia is using new sorting technology to produce whiter grades
engineered for improved flow by compaction into spherical agglomerates. This compacting increases the bulk density of HTP1S to approximately 0.6 g/ml compared to 0.26 g/ml for standard powders while the spherical shape minimises friction during material flow and enables bulk density to be retained. Malacari says HTP1S is recommended for applica- tions where the product has to be manually handled or for use in a premix of additives in the compounding process. In the latter case, HTP1S talc is said to give the blend the high flowability required so that accurate levels of all additives can be incorporated into the
formulation during the dosing phase. The HTP1S spherical talc agglomerates are soft and easily dispers- ible in the compounding process, the company says. Another new introduction from IMI Fabi is HVTultraC. This is an ultrafine micronised talc with an improved impact-to-stiffness balance in TPOs compounds, where low temperature ductile behaviour along with high stiffness and dimensional stability are required. The company says it can also be used in engineering polymers. Other solutions for lightweighting applica- tions in automotive compounds are in development, notes Malacari. Meanwhile, IMI Fabi’s NB240 grade is designed for
antiblocking applications in PE film extrusion, where it is claimed to provide an optimal balance between antiblocking, transparency, and slip properties. The grade is also said to minimise equipment wear compared to some other harder minerals.
Milled improvement Talc is mined from natural deposits and each ore source produces material with its own characteristics, including platelet size, says Imerys Performance Additives. Mined talcs are then further processed to create fillers that impart specific properties in plastic compounds. In February of this year, Imerys added two new products to its High Aspect Ratio (HAR) talc family,
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PHOTO: IMI FABI
PHOTO: IMI FABI
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