Polymer foam | technology
Clariant’s new Hydrocerol CFAs are said to help avoid these dosing and dispersion problems while making it possible to achieve a highly uniform structure of cells as small as 50-100 microns in diameter. This compares very favourably to the 400 microns typical using first-generation foams and even the 200 micron cell size considered “fine” until recently. “The most important thing is to listen to what the customer needs,” says Kerstin Schrinner. “They told us they had some serious concerns about using CFAs in bottles. This new Hydrocerol formulation helps to solve them all.” Another supplier of CFAs, Polyfil Corp, says it has changed its focus away from its product line of conventional endothermic foaming agents in favour of its Ecocell technology (it will, however, continue to produce endothermic formulations for existing customers). The company says that Ecocell produces finer cells and overcomes problems such as dual decomposition temperatures, which are common with typical endothermic products. According to Polyfil, Ecocell is finding uses in
processes where cell size and aesthetics are critical, such as thermoforming and blow moulding. Meeting requirements for food contact, the product is now being used in polypropylene thermoformed food packaging for produce and baked goods. It is also being used in blown polyethylene films for non-load applications such as water barriers. “Ecocell is a preferred nucleant for polypropylene foams producing the least amount of open cells compared to talc and conventional endother- mic CFAs,” according to a company spokesperson. Polyfil has also introduced an Ecocell grade for use with TPOs and TPEs. Bergen International, which offers a wide range of both endothermic and exothermic CFAs - including combinations of the two types - recently introduced Foamazol 14. This is an exothermic CFA supplied in the form of compound microbeads rather than a concen- trate, designed especially for rotomoulding. Brandon
Andorka, Director of Technical Services and Develop- ment at the company, says this makes it very easy to handle since no further mixing is required on the part of the user. Rotomoulders will typically use Foamazol 14 in the
middle layer of a part, feeding it into the mould via the drop box or through the vent tube. The microbeads help produce a smooth and even foam layer, Andorka says, adding that the company has custom formulated the chemical foaming agent in the product to control its decomposition to help uniformity of cell size and foam dispersion and to minimise voids. A novel topic discussed at the AMI
Polymer Foam conference was physical foaming of polymers using embedded gas-filled expandable microspheres. Embedded micro- spheres in a plastic melt act as expanding fillers and provide a variant of physical foaming that yields a three- phase system: the blowing gas, the thermoplastic shells of the microspheres, and the thermoplastic matrix. Carl-Otto Danz
and Karl-Christian Danz from KCD Kunststoffe Additive und Beratung discussed the use of expandable micro- spheres produced with a shell in polyacrylonitrile (PAN) and filled with a low boiling point alkane. When heated, the sphere skin softens, the liquid boils, and the spheres expand dramatically. They said the diameter will
Figure 3: Cost reduction analysis of the use of expandable microspheres in production of an extruded PVC-U ‘wavy’ construction profile
Cost of PVC-U-Blend
Cost of PVC-U-Blend with 1 wt. % microspheres batch Density of PVC-U profile without foaming
Density of foam-sheet with 1 wt. % microspheres batch Material cost saving due to foaming with spheres Source: KCD Kunststoffe
www.compoundingworld.com
1.30 €/kg 1.44 €/kg 1.40 g/cm3 0.90 g/cm3
+ 10.8 %
- 35.7 % - 24.9 %
Above: Bergen supplies its
Foamazol 14 CFA as a
microbead compound for
simple handling in rotational moulding
applications
Left: Foamazol 14 from Bergen is intended for production of foamed core layers in rotationally moulded parts
January 2017 | COMPOUNDING WORLD 69
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