additives | Polymer foam
Right: Automo- tive demands for lighter
weight and improved
surface quality are being
targeted by Imerys with its MIstrocell mineral
nucleator
as well as high performance industries, primarily to reduce the amount of materials used. In most cases, weight reduction would also result in less CO2
emis-
sions and greater sustainability,” he says. “Consequently, as chemical blowing agents usually
are supplied in granulate forms containing a carrier, it will be necessary to think about carriers that can withstand or melt at higher temperatures. In future, we anticipate an increase in the types of different particle foams (bead foams) available on the market. Currently EPS, EPP, and ETPU to some extent dominate the consumer markets. However, the design freedom that such materials provide is a big driving force for other polymers to enter the market,” Bahrami says. Recent developments at Clariant Masterbatches include the introduction of a new nucleating agent - Hy- drocerol NUC 6000 – said to enable production of finer cell sizes. Speaking at last year’s Polymer Foam conference, Patrizia Scholz, Product Development Additives at the company, described how nucleation with NUC 6000 could achieve cell sizes of less than 50 microns, which she said compared with a cell size of around 130 microns for active nucleation with a chemical foaming agent and 230 microns using passive nucleation with a standard talc. Scholz added that a smaller cell size is a key advantage in providing higher compression strengths at lower densities.
Mineral nucleation Imerys Group has been developing a variety of mineral fillers to provide functional characteristics such as high cell nucleation, which can be used to achieve polymer foams with improved mechanical properties and so further extend their scope of application. The company says controlled cell size results in improved mechanical properties and dimensional stability, allowing manufac- turers to reduce material cost. The latest nucleating
grade from the Imerys Talc division of the company is Mistrocell, a new talc range designed for production of lightweight materials with improved stiffness at lower density. Mistrocell is described as a micro-lamellar talc,
where the surface area of each talc particle depends upon individual platelet size. Imerys says that a lamellar talc has large individual platelets, whereas a micro-lamellar talc has smaller ones. Because the individual micro-lamellar talc platelets are smaller, the active surface area available for nucleation on each is higher. The result is that cell nucleation with micro- lamellar talc is far more efficient than with lamellar talc, says the company. Foam cell densities are claimed to be twice as high with Mistrocell compared with PP foams containing lamellar talc while the higher surface area of the micro-lamellar talc also enables more gas to be entrapped, which generates more cell nuclei. Caroline Abler, Development Manager Polymers at
Imerys Talc, said at the Polymer Foams conference that as a foam nucleating agent, Mistrocell offers good results in terms of cell structure. These improved results include the generation of finer cells, cell aspect ratio close to 1, more homogeneous structure and higher cell density. Storage modulus is also improved and reinforcement is better when compared to unfilled PP.
US-based Trexel, which developed and continues to
Cross-section micrograph of FEP wire insulation foamed with Colorant Chromatics Chemical Foaming technology showing the consistent cell structure, which helps preserve mechanical and electrical performance
42 COMPOUNDING WORLD | January 2016
market the Mucell physical foaming process for injection moulding applications, has decided to extend its foaming options to include chemical technology. The company has reached an exclusive greement with US-based Polyfil allowing it to market TecoCell chemical foaming technology for injection moulding applications (Polyfil will continue to market its EcoCell line of CFAs for extrusion opportunities). “While we are well known for our MuCell physical
www.compoundingworld.com
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