Structural recovery memory

Memory effects play an important role in structural recovery (18), as can be seen in Figure 12.21, where illustrative plots of the evolution of volume with time for different thermal histories are shown. Curve 1 presents the... 

The decrease in volume during physical aging is specifically known as volume recovery or volume relaxation. Volume recovery experiments include down-jump, up-jump, and memory experiments. The results of these experiments, which are shown and discussed later, demonstrate that structural recovery is both nonlinear, nonexponential and path-dependent. 

Rampon, C.,Tang,Y., Goodhouse, J. etal. Enrichment induces structural changes and recovery from nonspatial memory deficits in CA1 NMDAR1-knockout mice. Nature Neurosci. 3 238-244, 2000. 

The nickel-titanium orthodontic wire (Nitinol, 3M Unitek, Monrovia, CA, USA) that was first marketed [6] had a heavily cold-worked stable martensite structure [25], but superelastic wires [21] were subsequently introduced and followed [34] by wires having shape memory in the oral environment [7]. For the most efficient treatment, the archwire that is bent by the clinician for treating malpositioned teeth should return completely to the initial undeformed state during the process of tooth movement. Complete recovery will not occur for superelastic wires if there is permanent deformation [33], whereas full recovery will take place for nickel-titanium wires with in vivo shape memory. 

More sophisticated versions of SMPs are those based on the so-called cold hibernated elastic memory as self-deployable intelligent structures (Sendijarevic, 2003). This technology is based on polyurethane foams whereby shape memory effect is combined with elastic recovery of the foam, thus allowing them to be packed into the smallest possible form and inserted into the body via catheters. Given the foam s excellent biocompatibility, porosity, and lightness, they can potentially be used in many other forms, e.g., orthopaedic braces and splints, vascular and coronary crafts, as well as other equally vital prosthetics and implants. 

Tobushi, H., Hashimoto, T., Ito, N., Hayashi, S., Yamada, E., 01/1998. Shape fixity and shape recovery in a film of shape memory polymer of polyurethane series. Journal of Intelligent Material Systems and Structures 9 (2), 127—136. http //dx.doi.org/10.1177/... 

When the gel content was low (e.g., 40% or less), the samples did not recover fully upon heating. On the other hand, when the gel content was high, the complete final recovery rate was obtained indicating the requirement of a network structure to achieve the property of shape memory effect. 

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