technical paper | Foaming polyolefi ns Foam Density: Tables 3 and 4 show the results of the
foam density for packaging sheet materials with a thickness of 0.8 and 11 mm respectively. A comparison is made between production with a regular grade and with 2202UMS. Both products had comparable cell size and cell structure. The recipe contained PE, isobutane and talc. The product was cured to stabilize the growing process and degassed. In this situation it was possible to reduce the density of the regular product by approxi- mately 9-10%. These results are in line with results achieved at different locations. Average cell size: The average cell size was
measured with a stereo microscope. A typical picture is shown in Figure 9, while statistical data is published in Table 5. The product produced with the regular grade had a density of 22 kg/m3
with the UMS grade had a density of 20 kg/m3
Figure 9: Assessing cell size via stereo microscope
conductivity of the material. Another potential opportunity for this grade is to
help fulfi l certain fi re classifi cations. In Europe, new fi re classifi cations (Single Burning Item) are currently generating interest in the foam industry. By reducing the material density while maintaining the other properties, it is possible to improve the results in this new European fi re test. The ability of 2202UMS to reduce the waves or
corrugation in physically foamed sheet material has been proven in practice. For certain application and product densities, it is even possible to reduce the number of waves to zero. However, because of the other foaming behaviour of 2202UMS, it is also possible to maintain the number of waves at a fi ner cell structure. The various product properties obtained using 2202UMS are covered below, including foam density, cell size and structure, compression stress, and resilience.
, while the product produced . In this
situation, the number of waves in the end product was comparable, while the average cell size was reduced by 5% even with the density reduction of 9.8%. It is likely that an increase of the density of the foam produced with 2202UMS would make the cell size even fi ner. This is because reducing the blowing agent will lead to an increase of pressure, resulting in fi ner cells. Cell structure: The cell structure was measured via
SEM microscopy. Figure 10 shows a typical cell fragment of regular foam, while Figure 11 shows a typical cell-fragment of foam produced with 2202UMS. Not only is the average cell size smaller for the foam produced with 2202UMS, but also the cell walls are more homogeneous and thinner. Compression stress: The compression stress was
measured according to ISO 7217 and the results are compared in Table 6. The foams had a thickness of approximately 11 mm, and the foam density of the product produced with grade 2102TX00 was 21.1 kg/m3
Figure 10: cell fragment of regular foam 52 COMPOUNDING WORLD | January 2013
Figure 11: cell fragment of foam produced with 2202UMS
www.compoundingworld.com
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