Shape memory fixity

Strained silicon wafers, in scaling to deep submicron dimensions, 22 256 Strainers, in refrigeration systems, 27 539 Strain fixity rate (R ), in testing shape-memory polymers, 22 361... 

Cross-linked PUs with shape memory properties were prepared by Galia, Meier et al. using linear polyols synthesized by ADMET [140]. In this work, ADMET of a 10-undecenoic acid-derived a,co-diene containing a hydroxyl group was performed in the presence of 0.1 mol% of C4. 10-Undecenol was used as chain stopper, and the mixture of oligomers and diols (from 10-undecenol SM) obtained was cross-linked with MDI. The PUs obtained displayed outstanding values of strain fixity and recovery. 

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/... 

Features Good shape memory properties Improved properties on phase 1 Body temp, responsive Fixity under lower temp. Elasticity under common. Larger shrinkage Stable tensile modulus Multifu notions. 

Shape memory (SM) properties are typically quantified by the shape fixity (ffj) and shape recovery ratios (/ ,). means the extent of fixing of the externally applied deformation in the temporary shape. Its value is 100% when the applied deformation, introduced above is fully kept below in the temporary... 

Shape-memory properties can be quantified in cyclic, stimuli-specific mechanical tests [23,40]. Each cycle consists of the SMPC and the recovery of the original, permanent shape. From the data obtained, the shape fixity ratio (Rf) and the shape recovery ratio (/ r) can be determined (see, e.g., [40-42] and Chapter Characterization Methods for Shape-Memory Polymers in this volume). Rf describes the ability of the switching segment to fix a mechanical deformation, e.g., an elongation to applied during SMCP resulting in the temporary shape. Rr quantifies the ability of the material to memorize its permanent shape. Different test protocols have been developed. They differ in SMCP, which can be performed under constant strain or constant stress conditions (see Chapter Characterization Methods for Shape-Memory Polymers in this volume). The recovery process under stress-free condition enables the determination of the switching temperature Tsw for thermally-induced SMP. 

In this section, the sterilization and biocompatibility of SMPs are discussed jointly. All proposed SMP medical devices evenmally have to be validated with a designated sterilization method before they can be used clinically. The method of sterilization can influence the biocompatibility and performance of a device [104, 105], Subsequently, sterilization can also alter the thermomechanical properties of the polymer, which directly influence shape-memory properties such as shape storage (fixity) and recovery [106]. Currently, there are three types of sterilization methods including heat, radiation, and chemical techniques. 

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