MATERIALS | FOAMED SHEET
Translucent technology
At the recent Polymer Foam confer- ence in Hamburg, Germany – organ- ised by AMI – Lutz Boehnke, senior manager at Covestro in Germany, told delegates about the challenges and benefits of developing translucent foam. Translucency is achieved through a
combination of cell structure, cell size, surface roughness and sample/layer thickness, he said. “Fine cellular foams have a higher density of cell walls and cell struts –
which act as scattering centres,” he said. The difficulty in setting the level of
translucency was partly because there are few scientific studies on the subject. “For PU foams, they are non-exist-
ent,” he said. Translucent foams require a coarse cell structure and large cell struts, in order to minimise absorption. As long as the incident light is not absorbed, it can be scattered without a decrease in light intensity – other than for
der Meer, an engineer in market development and technical Support. “We have created innovative recipe designs of our new grades with additional value due to improved foam quality and increased process efficiency.” The new grades can enable better surface quality and smaller cell-size, with potentially improved mechanical properties due to their improved reactivity, said the company, which has carried out several customer trials in Asia to confirm this. The improved reactivity of the two grades to
cross-linking can result in more efficient process- ing, with shorter cycle times or faster line speeds, typically leading to a more competitive product and added value, said the company.
Chemical foaming Momentum International, a German additives producer, has developed two new chemical foaming agents for use in extruded products. Microcell 547 and 548 are new chemical foaming agents aimed at applications in foamed film and sheet. The aim of the development was to
back-scattering (if side-scattering can be avoided through reflectors). The foams are aimed at applica- tions such as translucent panels for buildings – for both interior and exterior use. n The next Polymer Foam conference is held in Pittsburgh, USA on 18-19 June 2019. For more details, visit the conference website, or contact organiser Christa Beveridge (
christa.beveridge@
ami.international) on +1 610 478 0800.
obtain foaming agents that improve the cell morphology and broadens the foaming window of PP and HDPE. “We focused on density reduction at low dosing
levels, and surfaces without any defects such as streaks,” said the company’s Klaus Gerhardt. “We were able to obtain these properties with our Microcell 547 at dosing levels of 0.8-1.0% in HDPE. Microcell 547 enables the processor to extrude foam sheet and film with glossy surfaces.” Microcell 547 uses a microporous powder to
create a large number of nucleation sites. This gave cell sizes of 50-100 microns in size. On the other hand, Microcell 548 uses a
nucleation agent with a particle size of around 8 microns, which also increases the crystallisation temperature of PP by around 15°C. This leads to faster production cycles but is low enough not to obstruct bubble growth. Trials on a 35mm Reifenhäuser with polypropyl- ene (PP) showed densities of 0.45-0.50 g/cm3 0.55 g/cm3
and in HDPE at dosings of 0.8% for both
products, without impairing surface qualities in extruded sheet and profiles.
� SUPER G®
4000 3500 3000 2500 2000 1500 1000 500 0
HighSPEED™
SGHS3000-36D Example PP Output
1814 1588 1361 1134 907 680 454 227 0
200 400 600 800 1000 1200 1400 Copolymer
RPM Homopolymer EXTRUSION SYSTEMS
high density manufacturing solutions that yield high production outputs with small machinery footprints.
SUPER-G®
HighSPEED™
extruders offer 55
lbs/hr
kg/hr
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