INNOVATION | DESIGN
so the floor can be cleaned. Rätsch also wanted to design a cantilever chair, which is a challenging chair type when using thermoplastics. “The Crastin PBT with its strength and stiff
Above: BASF is integrating its support for innovation projects with customers. Left to right: Dr. Uwe Seemann, Trend Scout, Eva Höfli, Designer and Helge Weiler-Schlecker, Simulation Expert
injection moulding technology (GIT), which results in a lightweight but strong structure. Using its Ultrasim software BASF said it was able to account for the actual shape of the gas bubbles for the first time in a structural simulation. “In a realistic process on the computer, first the component is volumetri- cally filled with melt; in a second step, the gas is injected, forming a gas bubble as in the actual injection moulding process. The internal geometry generated through the process simulation with GIT is then used for the strength calculation in the structure simulation.”
Right: DuPont Performance Materials worked with designer Frederic Rätsch on his Double Cantilever Chair
BASF is not the only polymer producer to become involved in the design of chairs that showcase plastic materials in a combined function- al and aesthetic manner. In June 2017, a collabora- tion between DuPont Performance Materials (now part of DowDuPont) and designer Frederic Rätsch, called ‘Flexible Seating in public spaces’, was displayed at the Royal College of Art gradua- tion show in London. The engineering plastics group provided its materials and manufacturing expertise in the creation of Rätsch’s Double Cantilever Chair, which uses Crastin PBT in the frame and Hytrel thermoplastic elastomer (TPC-ET) in the seat. The chair is intended for use both indoors and outdoors at cafés, libraries, universities and so on. The flexible seating concept is applied in different ways: the flexible Hytrel material allows variable sitting postures; the chair is also flexible in relation to its environment, for example it can be put on a table
68 COMPOUNDING WORLD | March 2018
properties is an adequate material to support the seat shell, while still allowing some flex,” said DuPont. “The design process was driven by a constant exchange between the computer and full-scale model making. CAD models are used as a tool to record the process and allow FEA [finite element analysis], stackability tests and arrange- ments in the chair’s context.” In the prototyping phase, wire and cardboard models were made to help define the design idea, and then models in polystyrene foam or plywood enabled the basic seating comfort to be assessed. DuPont said that in the final phase of the chair’s development, the Institute of Plastic Processing (IKV) of the RWTH Aachen University, Germany, made a full-scale prototype with its large 3D printing technology, using Hytrel for the seat shell to showcase the intended flexibility. Eastman has provided the material and techni- cal support for another plastic chair called Luxtiera from Japanese group Kawajun, which produces furniture and accessories for hotels and other public settings. The clarity of Eastman’s Tritan copolyester is highlighted in the seat of Luxtiera which is intended for public spaces and commer- cial usage including premium hotels, restaurants, hospitals and offices. A diamond pattern is moulded throughout the
chair’s seat and back, which presented a challenge in material selection. Nanae Imbe, Chief Designer in Kawajun’s Planning & Development Group, said: “We knew this design was too demand- ing for polypropylene, the plastic used in traditional chair applications. We looked at other options, but PMMA didn’t give us the toughness nor the chemical resistance we wanted—and polycarbonate lacked the chemical resistance we needed for durability.” Eastman said the properties of
Tritan make the chair easier to process and give it greater impact strength and resistance to body oils and environmental cleansers. Tritan also makes the chair more comfortable and softer feeling for the end user, it said. Chairs are a new area for Tritan copolyester, which Eastman has targeted largely at food and drink applications. A recent
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