A plastic that remembers

A plastic that remembers
Bayer MaterialScience and BAM Federal Institute for Materials Research and Testing develop shape memory polymer from thermoplastic polyurethane

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 a plastic can be temporarily reshaped and fixed in this shape. 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 approximately 40 °C. The abbreviation SMP stands for the English designation for such plastics: Shape Memory Plastics.

“Given this special property, there are virtually no limits to the potential applications for the plastic,” says Jürgen Hättig, Head of Business Development for TPU at Bayer MaterialScience. “We can imagine applications in areas ranging from mechanical engineering and the automotive, textile, sports and leisure industries to toy manufacturing and aerospace engineering.” Possible applications include the easy repair of damaged bodywork parts using a hair dryer, remote temperature sensors, artificial muscles, hinges, self-loosening screws, packaging and shrink tubing.

The two partners recently submitted a patent application for a possible application in the area of functional film tunnels and self-erecting structures. Film tunnels in a field act like greenhouses and accelerate the growth of lettuces and vegetables so that these can be harvested sooner than is possible if allowed to mature in the “classic” manner under the open sky. While it is easy to lay flat films on a field, erecting a permanent tunnel with films can be a time-consuming and costly operation.

This is an opportunity for the new shape memory polymer. Profiles made of the new TPU plastic that have temporarily been brought into a flat shape are fastened to the transparent film. After the film has been laid on the bed, all that's left to do is to heat the profiles to the switching temperature. 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.

The new material could also prove useful in product and brand protection applications. The BAM has used the TPU product to develop labels with engraved and 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 Dr. Thorsten Pretsch, Head of the BAM department for the investigation of shape memory polymers. The project for labels with switchable readability is funded by the German Ministry of Education and Research.

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


sent: 2012-08-10 14:03:21

If you have ever had a TPU case, this one is typical in feel and fit. In fact, the TPU-cases fit is perfcet in every way. The necessary cut-outs for the camera, mic, and power button are spot on for the Sprint Galaxy II S Epic 4G Touch. I like the fact that the recessed power button has a cut-out hole because it is used so often. On the other hand, the volume rocker, which sticks out slightly, is covered by the case. The look is a bit different because you can order matte backs. This is similar to the difference between the Sprint Evo backs that have a rubbery substance on them and the Samsung Nexus backs that have glossy plastic. At TPU-cases, you have a really large selection of designs and textures. I like the different matte look, and TPU are my favorite case type because they are the least intrusive, fitting tight against the phone while having a soft feel. They are easily removed for battery replacement, and you don't feel as if you might break the case at any second as you do with hard cases that have small plastic prongs holding the case together. The nice thing is that the TPU cases are inexpensive, so you can swap out the look and feel anytime you want. Finally, I have found any type of hard case to eventually scratch glossy phones. (No matter how careful you are, small pieces of dirt and sand wedge between the case and the phone.) Not so with TPU cases. I compare the difference between TPU cases and hard cases to the difference between a condom and a chastity belt: They are both effective, but one is much more comfortable.


sent: 2012-09-04 11:56:48

Thanks for the post. I would prefer to the strong plastic.