Bayer MaterialScience shape memory polymer

Co-developed by BAM Federal Institute for Materials Research and Testing in Germany and Bayer MaterialScience, the new thermoplastic polyurethane (TPU) can be temporarily reshaped and fixed in that shape. When heated to a certain temperature-known as the switching temperature-the plastics "remember" their original shape and return to it virtually unchanged. In the case of the new product Desmopan DP 2795A SMP, produced by Bayer MaterialScience, the switching temperature is approximately 104-deg F (40-deg C). (View a short video clip of a piece of plastic returning to its original shape at www.packagingdigest.com/SMP.)

Because the TPU material is free from plasticizers and antihydrolysis agents, it is also suitable for food contact applications. And it boasts the typical advantages of TPU, such as high abrasion resistance, flexibility and good chemical resistance.

The BAM has used the TPU product to develop labels engraved with colored 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," says Thorsten Pretsch, head of the BAM department for the investigation of shape memory polymers. 

The research project for labels with switchable readability was funded by the German Ministry of Education and Research (BMBF). It tested SMPs potential as specialized information carriers and concluded that tagging products with these information carriers is expected to be helpful for secure one-time identification.

To enhance surface contrast, BAM had surface-specific dyeing processes developed. QR codes printed on polymer surfaces were rendered temporarily unreadable as they were reshaped via thermo-mechanical programming strategies. Once thermally switched, the polymer recovered large parts of its permanent shape, which enabled error-free decoding of the QR code by a typical scanning and decoding device. 

According to BAM, labels printed on SMP provide significantly more effective protection against imitation than conventional bar code labels or holograms. In industries where product piracy is a problem, BAM sees large market potential for labels with switchable readability.

Researchers at BAM are also studying whether shape-memory polymers could remember more than one shape (that is, multiple-shape memory behavior) depending on how various thermo-mechanical treatments might actuate the different properties. Scientists at the institute also explored the material's degradation behavior under various aging conditions.

In addition to its agreement with Bayer MaterialScience, the BAM is open to other licensing agreements or joint projects with industry partners as a spin-off to its research.

Other applications  not a stretch
Packaging is just one potential use of this technology. Jürgen Hättig, head of business development for TPU at Bayer MaterialScience, says, "Given this special property, there are virtually no limits to the potential applications for the plastic. We can imagine applications in areas ranging from mechanical engineering and the automotive, textile, sports and leisure industries to toy manufacturing and aerospace engineering."

If you are interested in more technical data, researchers Martin Bothe and Thorsten Pretsch published an article titled "Two-Way Shape Changes of a Shape-Memory Poly(ester urethane)" online May 29, 2012, in the journal Macromolecular Chemistry and Physics (www.packagingdigest.com/SMParticle). The abstract states:
"Phase-segregated poly(ester urethane) exhibits two-way shape changes under various constant stresses. Most distinct actuation (expansion on cooling and contraction on heating) can be detected when the maximum stress applied during a thermo-mechanical pretreatment approaches the point where deformation-induced crystallization of the poly(1,4-butylene adipate) soft segment sets in."

Additionally, you can access the patent application documents for "Security Label for Identifying Products" at www.packagingdigest.com/SMPpatent. The description explains: "The invention relates to a security label for identifying products comprising a layer comprising a shape memory polymer, wherein a surface profile comprising information for identifying the product is embossed in the layer and wherein the layer has a smooth surface in a first state and the layer has the embossed surface profile in a second state, wherein the security label is adapted such that the layer can be changed from the first or second state to the second or first state upon reading out the security label and to a connection means for connecting the layer to the product."

BAM Federal Institute for Materials Research and Testing, +49 30 8104-0. www.bam.de/en/

Bayer MaterialScience, 800-662-2927. www.materialscience.bayer.com

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