Leverkusen, Germany -- A new thermoplastic polyurethane (TPU) developed by Bayer MaterialScience together with the BAM Federal Institute for Materials Research and Testing in Berlin, Germany, shows that plastics can also have a memory.
Parts made of such SMP (shape memory plastics) can be reshaped and fixed in this shape. But when heated to a certain temperature -- known as the switching temperature -- they "remember" their original shape and return to it virtually unchanged. In the case of the new product, Desmopan DP 2795A SMP, the switching temperature is about 40°C.
"Given this special property, there are virtually no limits to the potential applications for the plastic," said Jürgen Hättig, head of Business Development for TPU at Bayer MaterialScience, in a BMS statement. "We can imagine applications in areas ranging from mechanical engineering and the automotive, textile, sports and leisure industries to toy manufacturing and aerospace engineering."
SMP characteristics may be exploited for easy repair of damaged bodywork parts using a hair dryer, as remote temperature sensors, artificial muscles, hinges, self-loosening screws, packaging and shrink tubing, BMS suggests.
The two partners recently submitted a patent application for use of SMPS in functional film tunnels and self-erecting structures. These agro-tunnels act like greenhouses, accelerating the growth of lettuces and vegetables so they can be harvested rapidly.
Erecting tunnels using films can be time-consuming and costly. But this offers opportunities for shape memory polymers. Profiles made of the new TPU are temporarily made into a flat shape and fastened to the transparent film. When the film has been laid on the ground, the user heats the profiles to the switching temperature, when they 'remember 'their bent, permanent shape and pop up to form a half-tunnel, lifting the films with them. The mini-greenhouses are then ready for use.
Another use for the SMP is in product and brand protection. BAM has used the TPU to develop labels with engraved and coloured quick response (QR) codes. The codes can only be read if the labels are in their permanent shape. "The labels are thus very well suited as a means of storing information to mark and identify products in a way that is very difficult to counterfeit," said Dr Thorsten Pretsch, head of the BAM department for the investigation of SMPs.
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