Shape Memory Polymers with Polymer Bi-Layers

Xie et. al. has created a shape memory material that contains multiple “temporary shape” through creating a layered polymer material.  This material was created by layering two polymers with different glass transition temperatures.  The first layer was made from a mole ratio of 1.6 mole Epon 826/0.4 mole NGDE/1 mole Jeffamine.  It was placed in the mold and cured at 100 deg C for 40 minutes.  The second layer was made from a mole ratio of 0.8 mole Epon 826/1.2 mole NGDE/1 mole Jeffamine.  This mixture was poured on top of the first layer and cured for an additional 40 minutes at 100 deg C.  Then the mold was post-cured at 130 deg C for 1 hour.  The first layer had a Tg of approximately 48 deg C and the second layer had a Tg of approximately 75 deg C.  The figure below shows the shape setting and recovery process.

In step 1, the molded shape was heated to 90 deg C.  Then a deformation stress was applied.  The sample was then cooled under stress to 56 deg C.  The stress was release to create temporary shape B.  Shape B was then further deformed under larger stress and cooled to below 20 deg C.  The stress was released to create temporary shape C.

(1)  The molded shape was heated to 90 deg C. Then a deformation stress was applied. The sample was then cooled under stress to 56 deg C. The stress was release to create temporary shape B. (2)  Shape B was then further deformed under larger stress and cooled to below 20 deg C. The stress was released to create temporary shape C.  (3)  The polymer was heated to 56 deg C and shape B was recovered.  (4)  The polymer was heated to 90 deg C and shape A was recovered.

References:

1.  http://onlinelibrary.wiley.com/doi/10.1002/marc.200900409/full

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