MATERIALS | MINERAL FILLERS
The company also offers a way of improving barrier in monolayer food packaging. “Latest tests in polyolefins and biopolymers show that with KMI’s ultra-fine mica types it is possible to reduce water damp and oxygen permeability significantly, even by low filler addition,” she says. “Again, the trick is the combination of suitable mineral raw material with a special grinding technology to achieve finest products which are still flaky. The platelets provide the barrier, and the fineness supports the dispersion in the compound.”
Talc alternatives Not all minerals are as geographically widespread as CaCO3
and kaolin. Calcined Neuburg siliceous
earth, for example, is only found near Neuburg in Germany and Hoffmann Mineral is the only company mining it. But its properties make it interesting to plastics companies working in several diverse areas. During the Mineral Fillers Virtual Summit held in March by Compounding World publisher AMI, Félix Vicente Mondéjar, Area Sales Manager with the company, discussed applications for the mineral, which include use as an alternative to premium talc in PP (where it can provide better
impact strength and scratch resistance); as an impact modifier and warpage reducer in PA; as an anti-block agent in PET film; and as an IR absorber in LDPE greenhouse films. Use of mineral fillers to improve various proper- ties in bioplastics also came up in a presentation from Imerys at the same AMI summit. In this case, the mineral in question was talc. Imerys offers talcs branded Steamic and HAR. Anaïs Berjeaud, Technical Support Manager Polymers EMEA, says they provide significant improvements in flexural modulus of PLA, for example, and increase melt strength. Steamic talc used as a nucleating agent can significantly reduce crystallisation times too. On top of this, because of its high aspect ratio, HAR talc can double barrier to oxygen and moisture in PLA film at a 20% loading level. Canada’s Trinity Resources, which is in the
process of rebranding to Trinity Performance Minerals, is introducing its Altibright aluminium silicate-based high performance reinforcement additives as a talc replacement for polyolefin compounds. It is mined and produced in Newfound- land, and is currently available for market applica- tions in North America and Europe. Company president John Hurley says it provides extremely high brightness and high aspect ratio properties. Key properties cited by Hurley include high wet brightness, zero asbestos-form mineralogy, extremely low iron oxide content (less than 0.15%), and undetectable levels of carbonate. “Perfor- mance results at 20% and 38% reinforcement levels either matched or exceeded several incumbent talcs when comparing colour, impact, tensile and flexural test results,” he says. Grades are available in 2, 4 and 6 median micron sizes. Trinity has reserves in excess of 35m tonnes and Hurley says the company has developed a “zero waste” mining process that provides sustainable supply and price stability. “Combined with the implementation of a robust Environmental Social Governance Platform, Trinity Performance is guiding its operations to a net zero Carbon footprint by 2023,” he says.
Figure 2: Data showing the effect of various filler treatments on E-modulus and elongation at break in a number of different high performance PA compounds Source: HPF The Mineral Engineers
28 COMPOUNDING WORLD | June 2021
Surface modification At Quarzwerke Group subsidiary HPF The Mineral Engineers, Péter Sebö, Head of Marketing & Market Development, highlights the potential for development of functional filler systems for polyamides. “Some interesting new developments showed the possibilities of the replacement of high performance plastics (for example PPS) with some HT-PA grades,” he says. “For this reason, we have made recently a quite extensive investigation in
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