Polyurethanes having shape memory effects

Kim, Byung Kyu; Lee, Sang Yup; Xu, Min

doi:10.1016/s0032-3861(96)00442-9

Cited by 663 publications

(576 citation statements)

References 6 publications

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“…The strain recovery rate R r was calculated from m and the extension at the tension-free states P (N-1) and P (N) while expanding the sample in two following cycles N-1 and N after ref. 20: The total strain recovery rate R r,tot is defined as the strain recovery after N cycles, compared with the original shape (therefore p (N Ϫ 1) ϭ 0), and is typically given for the last cycle, n ϭ 5:…”

Section: Figmentioning

confidence: 99%

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AB-polymer networks based on oligo(varepsilon -caprolactone) segments showing shape-memory properties

Lendlein

Schmidt²,

Langer³

2001

Proceedings of the National Academy of Sciences

106

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Although shape-memory metal alloys have wide use in medicine and other areas, improved properties, particularly easy shaping, high shape stability, and adjustable transition temperature, are realizable only by polymer systems. In this paper, a polymer system of shape-memory polymer networks based on oligo-( -caprolactone) dimethacrylate as crosslinker and n-butyl acrylate as comonomer was introduced. The influence of two structural parameters, the molecular weight of oligo( -caprolactone) dimethacrylate and the weight content of n-butyl acrylate, on macroscopic properties of polymer networks such as thermal and mechanical properties has been investigated. Tensile tests above and below melting temperature showed a decrease in the elastic modulus with increasing comonomer weight content. The crystallization behavior of the new materials has been investigated, and key parameters for the programming procedure of the temporary shape have been evaluated. Shape-memory properties have been quantified by thermocyclic experiments. All samples reached uniform deformation properties with recovery rates above 99% after 3 cycles. Whereas strain recovery increased with increasing n-butyl acrylate content, strain fixity decreased, reflecting the decreasing degree of crystallinity of the material.M etallic alloys with shape-memory properties like NiTi alloys are already used in different areas, e.g., biomedical applications (1). § However, their mechanical properties can be adjusted only within a limited range, and they are not degradable.Here, we report an AB-polymer network showing shapememory properties. The advantage of this polymer system is its versatility. Several macroscopic properties such as transition temperature and mechanical properties can be varied in a wide range by only small changes in their chemical structure and composition.Shape-memory polymers are characterized by two features, triggering segments having a thermal transition T trans within the temperature range of interest and crosslinks determining the permanent shape. Depending on the kind of crosslinks, shapememory polymers can be thermoplastic elastomers or thermosets. By using this technology, shape-memory polymers potentially can be tailored for specific applications.For this polymer system, oligo( -caprolactone) has been selected as a crystallizable triggering segment that can fix a temporary shape by physical crosslinks. These segments were incorporated covalently into the thermosets. Therefore, oligo( -caprolactone) diols were functionalized with polymerizable methacrylate endgroups. The molecular weight of this macromonomeric crosslinker represents a first parameter on the molecular level to adjust crystallinity and mechanical properties of the polymer networks. For that purpose, especially for temperatures below the transition temperature, an additional monomer is introduced representing a second parameter. As comonomer, n-butyl acrylate, has been selected. Because of the low glass transition temperature of poly(n-butyl acrylate) [T g ϭ Ϫ55°C (2)...

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Section: Figmentioning

confidence: 99%

“…The strain fixity rate R f is the quotient of the extension in the tension-free state u (N), while drawing back the extension, and m (20):…”

Section: Figmentioning

confidence: 99%

AB-polymer networks based on oligo(varepsilon -caprolactone) segments showing shape-memory properties

Lendlein

Schmidt²,

Langer³

2001

Proceedings of the National Academy of Sciences

106

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“…Therefore, the softness was increases at elevated temperatures. Similarly, the hardness of the alloy was decreased with increasing in processing temperatures [16]. Fig.…”

Section: Resultsmentioning

confidence: 80%

Study of the Mechanical Behavior of LM20 Alloy at Various Temperatures Processed By Die Casting

Mashamba¹,

Avvari²

2015

Third International Conference on Advances in Mechanical and Robotics Engineering- AMRE 2015

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Abstract-Now a day's in the current domain, manufacturing industries are competing to reduce the cost and fuel consumption rates. Especially, in automobile and aerospace applications because of the improvement of lightweight metal advantages. Magnesium, aluminum and other few materials are considered as lightweight materials to use in required applications due to their inherent properties. Therefore, in this paper tried to characterize the advances of LM20 aluminum alloy rods by using the die-casting processes at various processing temperatures followed by room temperature, 373 K, and 473 K. The main aim is to study the effect of various processing temperature on microstructures and mechanical properties of LM20 alloy. Also, this paper reveals the stability of the microstructures of LM20 aluminum alloy though the processing temperature has been increased. The tensile strength, hardness of the LM20 aluminum alloy was decreased with increase in processing temperature. Similarly, the wear, and surface roughness tests were performed on the LM20 alloy rods to understand the effect at various processing temperature.

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“…For example, the recovery time of EFeZn25 is only 7 s while for EFeZn25H40, the recovery time reaches 20 s. However, when the recovery temperature of EFeZn25H40 is elevated to 60°C (Figure 13(c)), the recovery rate could be tuned to that achieved in EFeZn25, indicating the recovery rate is conveniently tuned. According to the reports by Kim et al [39,40], the sharp transition from glassy state to rubbery state is crucial to the material for use as SMPs. A high elasticity ratio between glass-state modulus and rubbery-state modulus (E g '/E r ') allows easy shaping at T > T g and good resistance to deformation at T < T g .…”

Section: Regulation Of Sme Of Zdf-cured Enr By Hntsmentioning

confidence: 99%

Sustainable shape memory polymers based on epoxidized natural rubber cured by zinc ferulate via oxa-Michael reaction

Zhang

Lin

Tang

et al. 2015

International Journal of Smart and Nano Materials

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Although various shape memory polymers (SMPs) or diverse applications have been widely reported, the SMPs based on rubbers have been rarely realized due to the low triggering temperature of rubbers. In another aspect, the SMPs based on sustainable substances are highly desired for the growing shortage in fossil resources. In the present study, we accordingly developed the sustainable SMPs with tunable triggering temperature, based on natural rubber (NR) and ferulic acid (FA) as the raw materials. Specifically, the SMPs are based on a crosslinked network of epoxidized natural rubber (ENR) crosslinked by in situ formed zinc ferulate (ZDF) via oxa-Michael reaction. The excellent shape memory effect (SME) is found in these SMPs, as evidenced by the high fixity/recovery ratio and the tunable triggering temperature. With the incorporation of natural halloysite nanotubes (HNTs), the stress and recovery rate of the SMPs are found to be tunable, which widens the application of this kind of SMPs. The combination of adoption of sustainable raw materials, and the excellent and tunable SME makes these SMPs potentially useful in many applications, such as various actuators and heat-shrinkable package materials.

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Polyurethanes having shape memory effects

Cited by 663 publications

References 6 publications

AB-polymer networks based on oligo(varepsilon -caprolactone) segments showing shape-memory properties

AB-polymer networks based on oligo(varepsilon -caprolactone) segments showing shape-memory properties

Study of the Mechanical Behavior of LM20 Alloy at Various Temperatures Processed By Die Casting

Sustainable shape memory polymers based on epoxidized natural rubber cured by zinc ferulate via oxa-Michael reaction

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