The Practice Question ask to Specify special type of SMP(Shape Memory Polymer) m

Question

The Practice Question ask to Specify special type of SMP(Shape Memory Polymer) materilas not in general.

Some shape-memory polymers (SMP) have relatively low glass transition temperatures, T_g. As glass transition occurs, the volume/shape of the SMP changes significantly. Typically, a shape-memory experiment consists of the following steps: (1) as T> T_g, the SMP has a specified shape ("A"); the temperature is lowered to below T_g; the SMP is deformed to another shape ("B"); the temperature is increased back to above T_g; it can be observed that the shape of SMP changes from "B" back to "A". The polymer under consideration is a thermoplastic. Do an independent literature research; describe in detail why the thermoplastic polymer has such a shape memory characteristic. If after the 4^th step, the temperature is changed to below T_g again, will the shape of SMP change from "A" to "B" again? Why? Clearly list all your references.

Explanation / Answer

The memory of a polymer depends on the recovery rate and the fixicity rate. Recovery rate is the ability of becoming to the initial position after deformation.

Amorphous polymers have more entanglements. They are realeased due to temperature. At tg entropy gets increased. Since such polymers have high strain recovery rate they can go to their startion positions making entaglements back.

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