Shape Memory Polymer Foam with Programmable Apertures

• Main Authors: Mario Walter, Fabian Friess, Martin Krus, Seyed Mohammad Hassan Zolanvari, Gunnar Grün, Hartmut Kröber, Thorsten Pretsch
• Format: Article
• Language: English
• Published: MDPI AG 2020-08-01
• Series: Polymers
• Subjects: foam; programmable material; polyester urethane urea; actuation; construction; air slot
• Online Access: https://www.mdpi.com/2073-4360/12/9/1914

In this work, a novel type of polyester urethane urea (PEUU) foam is introduced. The foam was produced by reactive foaming using a mixture of poly(1,10–decamethylene adipate) diol and poly(1,4–butylene adipate) diol, 4,4′-diphenylmethane diisocyanate, 1,4–butanediol, diethanolamine and water as blowing agent. As determined by differential scanning calorimetry, the melting of the ester-based phases occurred at temperatures in between 25 °C and 61 °C, while the crystallization transition spread from 48 °C to 20 °C. The mechanical properties of the foam were simulated with the hyperplastic models Neo-Hookean and Ogden, whereby the latter showed a better agreement with the experimental data as evidenced by a Pearson correlation coefficient R² above 0.99. Once thermomechanically treated, the foam exhibited a maximum actuation of 13.7% in heating-cooling cycles under a constant external load. In turn, thermal cycling under load-free conditions resulted in an actuation of more than 10%. Good thermal insulation properties were demonstrated by thermal conductivities of 0.039 W·(m·K)⁻¹ in the pristine state and 0.052 W·(m·K)⁻¹ in a state after compression by 50%, respectively. Finally, three demonstrators were developed, which closed an aperture or opened it again simply by changing the temperature. The self-sufficient material behavior is particularly promising in the construction industry, where programmable air slots offer the prospect of a dynamic insulation system for an adaptive building envelope.