"Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane"

Thursday, May 23, 2013: 12:30
Congress Hall 2 (OREA Pryamida Hotel)
Prof. Elzbieta Alicja PIECZYSKA , Institute of Fundamental Technological Research, Warsaw, Poland
Prof. Hisaaki Tobushi , Aichi Institute of Technology, Toyota, Japan
Prof. Shunichi Hayashi , SMP Technologies Inc., Tokyo, Japan
Dr. Katarzyna Kowalczyk-Gajewska , Institute of Fundamental Technological Research, Warsaw, Poland
Dr. Mariana Cristea , "Petru Poni" Institute of Macromolecular Chemistry, Iasi, Romania
Ms. Maria Staszczak , Institute of Fundamental Technological Research, Warsaw, Poland
Dr. Michal Maj , Institute of Fundamental Technological Research, Warsaw, Poland
Initial experimental evaluation of polyurethane shape memory polymer (PU-SMP) is presented.

Results of dynamic mechanical analysis suggest that the SMP (Tg = 19°C) fulfills some preliminary demands to function as shape memory polymer. Namely, a high glass elastic modulus Eg’(1500 MPa), proper value of the rubber modulus Er’(15 MPa) and a high ratio of Eg’/Er’(100) were obtained.

The SMP samples were subjected to uniaxial tension carried out at room temperature (23°C) at different strain rates till rupture. The true stress and true strain data were elaborated and temperature changes from the samples surface were determined using fast and sensitive infrared camera.

It was found that the SMP yield strength increases upon increase of the strain rate. The initial elastic strain is accompanied by the sample temperature decrease, called a thermoelastic effect. It is worth noting that the maximum temperature drop, related to the material yield point, also depends on the strain rate.

At higher strains, the monotonic stress increase was observed, related to reorientation of the polyurethane molecular chains. This stage is followed by the stress drop noticed at the strain of approximately 1.4. The stress drop can be related to the SMP crystallization phenomenon. After that the stress increases till the SMP rupture, observed for all the strain rates applied at the strain of about 1.8.

The higher strain rate, the higher temperature changes were obtained, since the process was more close to adiabatic conditions. The maximal values were 18K for 2x10-1s-1, 37K for 2x100s-1 and 44K for 101s-1.  

Basing on the mechanical characteristics and their relevant temperature changes, the SMP thermomechanical properties have been studied. Identification of the PU-SMP parameters for one-dimensional rheological model will be performed.

Acknowledgments: The research has been carried out with the support of the Polish National Center of Science under Grant No. 2011/01/M/ST8/07754.

See more of: Session 8: Shape Memory Polymers and Hybrids
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