Imagine a package that changes shape when you turn a hair dryer on it, or one that changes colour and shape in the sun and transforms back to its original shape in the shade. Shape shifting plastic is no longer the domain of science fiction, as research into many different types of 'smart' plastic material is increasing.
Shape memory polymers are plastics that can change into to a temporary shape, and then back to original form when subjected to changes in heat, light or pressure. This property has been achieved with several malleable polymers, but is difficult to do with thermoset plastic because it has strong cross-linked molecular bonding and is therefore 'stuck' in its final shape. However, scientists from the US Department of Energy’s Oak Ridge National Laboratory (ORNL), Washington State University and the University of Idaho have now developed a process that permits reshaping and reuse of thermoset plastic.
The study, published in the journal Macromolecule by Yuzhan Li et al., describes the new shape shifting plastic - a smectic main-chain liquid crystalline elastomer - with triple-shape memory, as seen in the photo below, which "can transform from one temporary shape to another temporary shape at one temperature, and then back to a permanent shape at another temperature," according to information from ORNL. The process allows for great flexibility in design and application - whether in manufacturing or packaging - but requires fine-tuning, says researcher Orlando Rios. In particular, controlling the ratio of chemicals during synthesis of the plastic will be key to managing the temperature required for the material's transformation.
According to the research team, the new technique is expected to have broad applicability in a range of industries, including the aerospace, medical and packaging industries, and a patent application has been filed.
According to Rios, the shape memory behavior could be used in the packaging industry by having a temperature dependent process for de-packaging something: "For example, you could use a hair drier to heat a part of the packaging, which would trigger the shape memory behavior and open the package; or ... a folded up package that can unfold when heated. Thermally activated color changing makeup could also be a possibility (if we can reduce the transformation temperatures).”
Another potential application of the material, according to Washington State University’s Yuzhan Li, is adjustable and re-usable packaging: "The material, such as a SMP film, can be deformed to nicely wrap products with different size and shape, allowing minimum use of the packaging material. And by heating the package to a higher temperature, the package can be easily opened and the packaging material will return to its original form for the next package.”
