Extrusion International 6-2019

51 Extrusion International 6/2019 SML is developing foamed sheet for hot fill applications with new features in terms of heat resistance, insulation and recyclability in a joint R&D programme together with its partner KIEFEL. The basis for these new products is a 3-layer PET (or PP) sheet with a physically foamed central layer. Mono-material foamed PET or PP sheet produced from SML’s new systems have outstanding product features that can help to replace difficult-to-recycle hot fill appli- cations made of expanded polystyrenes. Generally, PS is permitted for food applications, but it is considered to release the chemical compound styrene into the environ- ment. The foamed sheet from SML’s new lines has an A/B/A structure, in which the central B layer is foamed while the two outer layers are rigid. The central layer is physically- foamed with the injection of nitrogen or simple carbon dioxide gas which is widely available. Mono-material structures facilitate recycling while the foamed layer re- duces weight up to 50% compared to PET sheet with the same properties. No special additives are required to en- hance the heat stability of the sheet which is thus suitable for the economic production of low-weight cups with ex- cellent insulation properties. In a new joint R&D project, KIEFEL Technologies and SML are exploring and further developing the potentials and opportunities this type of foamed sheet is offering. Beside end products with very specific mechanical and thermal properties, the optimization of the manufacturing pro- cesses and the research on new recycling methods are in the focus of this research programme. The first outcomes are absolutely promising: cups boasting a heat resistance of up to 100 degrees Celsius have been created form stan- dard APET. The sheet for such cups can have an overall density of about 0.65 kg/dm³, which saves material and increases the insulating properties, so that it is possible to hand-hold these cups filled with extremely hot liquids. Unlike polystyrene, mono-material foamed sheet, espe- cially from PET, is straight-forward to recycle as the rel- evant infrastructure already exists in many places. Hot fill applications made of foamed PET sheet can be easily pro- cessedwith other single use products fromPET. This opens opportunities to branches as airline catering or system gastronomy which still rely on disposable items. When all products are from the same material, respectively PET, re- cycling processes are becoming truly effective – both with regard to ecological and economical aspects. A key element in the joint research programme of KIEFEL and SML is the new demonstration and development line for thermoforming sheet in SML’s Technology Centre. With a thickness range from 200 micron to 2 mm, the line offers a maximum of flexibility for all kinds of projects related to thermoforming. Except from this research pro- gramme, it stands open to SML’s customers and partners for trials and R&D. SML Maschinengesellschaft mbH www.sml.at Mono-Material Hot Fill Cups out of foamed PET Hot fill cups made of foamed PET: heat-resistant, insulating and easy recyclable